SpudFiles Wiki - User contributions [en]

User:Benstern

2012-11-24T06:00:02Z

Benstern: Blanked the page

Wantedpages

2008-06-15T19:27:36Z

Benstern: aded and fixed

I am making this as a page to list pages people want to see created. This page separate from the [[Special:Wantedpages|page from the special section]] which shows non-existent pages with links to them. These can either be a result of a wanted page or just bad linking.

==Building materials and construction==
*Threads
*Flange
*Cleanout
*Plug
*Cap
*Elbow
*Chamfering
*Teflon tape
*ABS
*Syringe
*Fire extinguishers
*Epoxy

==Accessories and improvements==
*Hop-up
*Suppressors
*Muzzle break
*Propane bottle adapter
*Propane bottle adapter how-to make
*Painting
*Ramrod
*Ballistic pendulum

==Theories==
*Blowby
*Automatic firing
*Semi-automatic firing
*Drag coefficient (CD)
*Cleaning
*Hang-time

==Fuels and related==
*Alcohol
*Hydrogen
*Methane
*Helium
*Oxygen
*Nitrogen
*Air
*CO2

==Valves==
*Gate valve
*Globe valve
*Hammer valve

==Tools==
*HCMP
*Launcher Range Calculator
*ProMeterSuite
*SpudTool

==Ammo==
*Airsoft BB
*0.177 BB
*Water

==Other==
*Spudfiles

Wantedpages

2008-06-14T21:09:34Z

Benstern:

I am making this as a page to list pages people want to see created. This page separate from the [[Special:Wantedpages|page from the special section]] which shows non-existant pages with links to them. These can either be a result of a wanted page or just bad linking.

==Building materials and construction==
*Threads
*Flange
*Cleanout
*Chamfering
*Plug
*Cap
*Elbow
*Teflon tape
*ABS
*Syringe
*Fire extinguishers
*Epoxy

==Accessories and improvments==
*Hop-up
*Suppressors
*Muzzle break
*Propane bottle adapter
*Propane bottle adapter how-to make
*Painting
*Ramrod
*Ballistic pendulum

==Theories==
*Blowby
*Automatic firing
*Semi-automatic firing
*Blowby
*Drag coefficient (CD)
*Cleaning
*Hang-time

==Fuels and related==
*Alcohol
*Hydrogen
*Helium
*Oxygen
*Nitrogen
*Air
*CO2

==Valves==
*Gate valve
*Globe valve
*Hammer valve

==Tools==
*HCMP
*Launcher Range Calculator
*ProMeterSuite
*SpudTool

==Ammo==
*Airsoft BB
*0.177 BB
*Water

==Other==
*Spudfiles

Piston valve

2008-06-14T21:04:08Z

Benstern: fixed link that I overlooked

A '''piston valve''' is a [[pilot]] operated [[valve]]. It is very similar to a [[diaphragm valve]] in theory, but replaces it's flexible diaphragm with a rigid cylinder. There are 2 varieties; [[barrel]] sealing and [[chamber]] sealing.

== Barrel sealing valve ==

In a barrel sealing valve, the piston seals against the breech of the barrel. This is the most common piston valve design.

=== construction ===

The piston is often a well fitting cup-shaped object, such as a end cap. To provide a sealing face, a piece of rubber is attached, typically with a bolt. In the simplest case, equalization is accomplished by allowing the air to leak past the piston and into the chamber. Some people will machine their own pistons, in which case they often build [[O-ring]]s into them. With the O-rings, you need to make a small equalization hole; sometimes this is fancied up to be a homemade [[check valve]].

Because a piston is heavier and harder than a diaphragm, and PVC is somewhat brittle, it is recommended that a bumper of sorts is built into your pilot volume. Common bumpers include heavy-duty rubber hose, and such. This is labeled "'''F'''" in the "use, barrel sealing" diagram.

These valves are often used on [[coaxial]]s and [[over/under]]s. In an over/under, the valve is built in a "T" fitting. The barrel is put co-axially through one end, the pilot and piston are put in the opposite one, and a chamber is connected to the perpendicular opening with a 90° elbow.

=== Use ===
[[Image:Wpiston.PNG|frame|top=pressurized, bottom=firing]]
Operation:
#Air is added by filling behind the piston (C).
#The piston (E) slides forwards, and seals against the barrel (A). (Alternatively, one can use a spring to move the piston forwards, which allows one to fill [slowly at first, to allow the [[pressure]] to equalize] from the chamber.)
#More air is added, and leaks around the piston (or through a small equalization hole) and into the chamber (B), filling it to the desired pressure.
#The [[pilot valve]] (D) behind the piston is opened, the pressure in the pilot volume (C) drops, and the higher pressure in the chamber area pushes the piston away from the barrel.
#The air flows around from the chamber, and into the barrel, propelling the projectile.

== Chamber sealing piston valve ==

=== construction ===

The piston of a chamber-sealing piston valve has to seal on both the chamber port and to the pilot volume. This requires that the piston be machined with [[O-ring]]s. A small equalization hole is required; sometimes this is fancied up to be a homemade [[check valve]].

The piston is almost always housed in a "t" fitting.

Because a piston is heavier and harder than a diaphragm, and PVC is somewhat brittle, it is recommended that a bumper of sorts is built into your pilot volume. Common bumpers include heavy-duty rubber hose, and such. This is labeled "'''F'''" in the "use, chamber sealing sealing" diagram.

These valves are often used on [[over/under]]s, as the flow is already turned around 90o.

=== Use ===
[[Image:Wcspiston.PNG|frame|top=pressurized, bottom=firing]]
Operation:
#Air is added by filling behind the piston (C).
#The piston (E) slides forwards, and seals against the barrel (A). (Alternatively, one can use a spring to move the piston forwards, which allows one to fill [slowly at first, to allow the [[pressure]] to equalize] from the chamber.)
#More air is added, and leaks through the equalization hole in the piston and into the chamber (B), filling it to the desired pressure.
#The [[pilot valve]] (D) behind the piston is opened, the pressure in the pilot volume (C) drops, and the higher pressure in the chamber area pushes the piston away from the chamber.
#The air flows out of the chamber, and into the barrel, propelling the projectile.

== Common traits ==

#The performance of these valves can be calculated with the [[GGDT]].
#If your valve [[honking|honks]], it is probably a good idea to invest in a better pilot valve, though this is more of a problem with barrel-sealing valves.
#In both cases, provided there is a good deal of space around the barrel, the full flow potential of the valve is realized when the piston has moved back 1/4th of the barrel's inside diameter.
#Pneumatic actuation is not mandatory; mechanical means can be used to hold the valve shut, rather than using the force of the air.

[[category:valves]]

Pneumatic air sources

2008-06-14T21:00:07Z

Benstern: added and fixed links

This page lists some of the common sources of air [[pressure]] to power a pneumatic, and the advantages and disadvantages of each:

==Gases==

'''[[Acetylene]]'''

Advantages:
* Very powerful combustion pressure spikes

Disadvantages:
* Extremely unstable, will auto-ignite at pressues over 15 psi
* Pressure spikes are very rapid, and therefore can cause fatigue much more readily
* Safe to use in very few spudding applications

'''Air'''

Advantages:
* It's price (completely free of course)
* Global availability.
* Inert

Disadvantages:
* Limited performance approaching the sound barrier.

Performance of air is moderate. It is very uncommon for a air powered launcher to exceed the sound barrier, but not completely impossible. Most gases are compared against air as a benchmark
Sources: If you want to use air, you'll either need a [[compressor]], [[Hand pump|hand/foot pump]] or a [[gas bottle|High Pressure Air (HPA) tank]]

'''Helium'''

Advantages:
* Exceptional performance
* High speed of sound and particle speed
* Inert

Disadvantages:
* Costly
* Will leak faster than any other gas
* Helium regulators typically limited to 200 psi.

Performance is second only to Hydrogen.
Sources: Unless you have an on-site extraction plant, the only option is [[gas bottle]]s

'''[[MAPP]]'''

Advantages:
* More powerful than propane, but still safe for [[pressure rated]] PVC

Disadvantages:
* More expensive than propane

'''Nitrogen'''

Advantages:
* Performance slightly better than air.
* Option for high pressures.
* Inert

Disadvantages:
* Costly
* Particle speed is not significantly more than that of air

Nitrogen is slightly more powerful than air for a given pressure, but nitrogen regulators are capable of very high pressures.
Sources: Unless you have an on-site extraction plant, the only option is [[gas bottle]]s

'''Hydrogen'''

Advantages:
* Highest performance gas, in terms of particle speed

Disadvantages:
* Costly.
* Potential explosive risk.
* Will leak fast.

Hydrogen is the most powerful gas that can be used in a pneumatic, but it has numerous risks associated with it.
Sources: Unless you have an on-site extraction plant, the only option is [[gas bottle]]s or electrolysis

'''Carbon Dioxide'''

Advantages:
* Reasonably cheap
* High pressure
* Highest gas volume to bottle volume ratio
* Inert

Disadvantages:
* Low power due to high molar mass and high density
* Very heavy cooling on decompression (can cause problems with [[PVC]] launchers)

CO2 is a very common bottled gas, but it's power is limited by it's high density.
Sources: [[Gas bottle]]s, [[CO2 cartridge]]

'''[[Propane]]'''

Advantages:
* Reasonably cheap
* High gas volume to bottle volume ratio
* Readily available

Disadvantages:
* Low power
* Low pressure
* Possible (if unlikely) fire risk

Propane is better known as a [[combustion cannon]] power source, but some pneumatics have used it as a gas. It's performance is low, because of it's high density and low pressures, but it is cheap and easily found.
Sources: [[Gas bottle]]s, either in large bulk tanks of several kilograms, or in small tanks of 0.5 - 1 lb.

==Supplies==

[[Compressor]]

[[Hand_pump|Hand/Foot Pump]]

[[Gas_bottle|Gas bottles]]

[[CO2 cartridge]]s

Copper pipe

2008-06-14T20:51:21Z

Benstern: fixed and added links

Copper pipe and fittings are popular spudgun construction materials due to their common availability in DIY stores. It is especially popular in countries such as the UK where pressure rated plastic piping is only available by order.

==Pros/Cons==

The primary advantages of copper pipe are that it is rated to much higher [[pressure]]s than PVC, and has better failure characteristics due to it's high malleability which results in splitting rather than shattering. This makes it well suited for making high pressure [[pneumatic cannon]]s and [[hybrid cannon|hybrid]]s. The pressure ratings have a safety factor of around 7.

Copper piping is typically very smooth and consistent, which combined with it's high rigidity makes it exceptional [[barrel]] material. The consistent internal diameter also makes it popular for construction of [[combustion cannon]] [[fuel meter]]s.

For comparable sizes of [[PVC]] it is around four times the price and considerably heavier, it is therefore only a viable alternative to plastic for small calibers of around 1" or less.

For comparable sizes of [[Steel Pipe|steel]] it is has a lower pressure rating and again is more expensive. However due to the thinner walls it is comparatively light and it is cheaper to make non-mechanical joins with.

==Types & Use==

Copper pipe is usually joined by [[sweating]], using [[compression fitting]]s, or [[Copper epoxy]].
Compression fittings are much more expensive than soldering ones but require minimal tools to use (a spanner or two), copper epoxy uses the same solder fitting as for sweating but replaces the solder to make the join therefore requiring no blowtorch.

The threaded fittings for copper pipe are made of brass or less commonly, corrosion resistant/coated steel as they have better mechanical strength than pure copper.

Copper pipe comes in two tempers, annealed and drawn. Annealed pipe is very soft, is sold in coils and can usually be bent by hand. Drawn pipe is rigid, sold as straight lengths and will flex rather than bend (to a certain limit). Bending drawn pipe without causing it to flatten out requires bending springs or mechanical bending devices which force the pipe over curved forms to create the desired shape without unwanted deformation.

Drawn pipe is the most useful in spudgun construction for [[chamber]]s and barrels, since it will keep its shape and not get damaged as easily. It is also rated to about twice the pressure as an annealed pipe of the same size. Small bore annealed tubing has a place in areas such as [[pilot]] tubing from the main [[valve]] to the [[pilot valve]] where it's higher malleability allows for pilot valve positioning.

==Safety==
Copper or Brass pipe/fittings should not be used with [[acetylene]] gas, as copper alloys can act as a catalyst to the explosive decomposition of the gas.

Due to it's relatively thin walled nature, potentially dangerous sharp ends can exist on pipe ends that have not been cleaned, and anybody using it should be aware of this.

Cutting of copper has a high attrition rate on rotary multi-tool abrasive discs, which will wear down at a high rate, and break apart regularly. Use of safety goggles is recommended

[[category:construction materials]]

Combustion cannon

2008-06-14T20:47:15Z

Benstern: fixed link

[[image:Basic_combustion.JPG|right|thumb|350px|Basic combustion cannon]]
A '''combustion cannon''' is a cannon powered by the combustion of flammable fuel-air mixtures. A basic combustion cannon is the simplest one to build, and is therefore often the choice for first time builders, though advanced designs with more power and useability are also possible. Most of the combustion spudguns are made out of [[PVC]] or [[ABS]].

Though being the simplest cannon of all, a well-made pneumatic or hybrid is usually more powerful then a combustion. The pressures in a combustion usually do not rise above 50-60 psi on [[spray and pray]] cannons and about 70-90 psi on advanced cannons. Jimmy101, a member of spudfiles showed that in closed chamber experiments the maximum pressure possible with a propane mix is a little more then 100psi in a closed chamber.

Potato guns are often painted to increase their aesthetic value and to cover unsightly primer stains. Krylon Fusion, a type of paint specifically made for plastics, is the most common type of spray paint used on potato cannons. Some combustion cannons have chambers made from clear pvc, this allows you to see the internals like the sparks and the fan (LED fans can be beautiful this way) and most importantly: a flash of fire on ignition.

==Basic elements==

* Combustion [[Chamber]]
* [[Fuel]]
* [[Ignition source]]
* [[Barrel]]

==Operation & Theory==

In order to fire, the operator loads a projectile (usually a potato) down into the barrel, adds [[fuel]] to the combustion chamber, like spraying [[aerosol]]s in the back end and screwing the cap on and then triggers the [[ignition source]] (e.g. a piezoelectric [[BBQ ignitor]]). The ignition system creates a spark in the chamber wich ignites the fuel. The fuel quickly burns up and the hot gases want to expand, creating pressure. The pressure acts out force on the back of the projectile and the air pushes the projectile out. Muzzle velocity and distance vary greatly mostly depending on the [[stoichiometry]] of the fuel/air mixture, the size and [[chamber to barrel ratio]] (C:B ratio) of the launcher and possible performance increasing additions like a [[chamber fan]].

The most basic spudguns use aerosols like hairspray, deodorant or [[starting fluid]] sprayed in at the back ([[spray and pray]]), while more advanced cannons usually use [[propane]] injection. Besides the difference of low-power aerosols and pure fuels like propane there is not much of a difference between fuels, the power of propane and butane vary no more then a few percent. Achieving the right stoichiometry (right amount of fuel and air/oxygen) is usually more important for the performance. Spray and pray cannons often have poor stoichiometry and thus inconsistent shots with relatively low power. Fast burning fuels like [[hydrogen]], [[acetylene]] and [[oxygen enriched]] mixtures are usually avoided, even if they may be a little more powerful, their fast burn rates and high chance of [[DDT]] create shockwaves that are powerful enough to rip any PVC or ABS chamber to shreds.

==Advanced improvements==

*[[Chamber fan]]
*[[Stun gun]], [[Flyback circuit|flyback transformer]] or [[camera flash]] ignition
*Multiple [[spark gap]]s
*[[Fuel meter]]
*A good [[C:B ratio]]
*[[Breech loading]] mechanism

The above improvements will increase the power and/or useability of the gun. View those pages for more information.

==Safety==
Non [[pressure rated]] "DWV" pipe is used so now and then in combustion cannons and it is generally accepted that this is safe with basic spray and pray; however some of these cannons have blown up. If you want to be safe you should definitely use pressure rated pipe and fittings, especially on advanced combustions.
As stated above specific fuels such as acetylene, hydrogen, and any oxygen enriched mixtures are not safe to use in a gun made out of PVC or ABS.
When using a normal fuel, pressure rated pipe and fittings and have properly [[solvent welding|solvent welded]] all of the joints, you can be considered 100% safe.

Some people, like parents think it is unsafe because it is an "explosion" and thus dangerous. In that case point them on the facts that it is just a [[deflagration]] and not a [[detonation]] creating no huge shockwaves, but creating just heat and pressure. This pressure is lower then the rated pressure of pressure rated pipe and fittings and that means the gun simply can't explode.

Note that cold weather makes pvc brittle and you should not use a frozen gun. However a gun that has been frozen some time but is up to normal temperature again is safe to use.
Dropping the gun isn't recommended, especially frozen guns, since this might create tiny cracks; a starting point for completely cracking open and blowing up.

==Legality==
Laws are different in each country, state or even city, check the [[legal issues]] page for more information. In some countries combustion cannons are illegal while pneumatics (possibly being way more powerful) may be legal.

Common Ammo

2008-06-14T20:44:37Z

Benstern: fixed links

== Description of the table columns: ==

; Ammo : The type of ammo. For ammo that is cut by the [[barrel]], such as spuds, this gives a typical length of the ammo. The length of the ammo and the barrel diameter determine the actual size of the ammo. For spuds, there is more than one way to [[potato#Selection, cutting and use|cut]] the shell.
; Mass : The mass of the ammo in ounces (oz.) and grams.
; Diameter : The diameter of the ammo in inches (") and centimeters (cm). For ammo that is cut by the barrel, such as spuds, this is the barrel diameter. For ammo that is not cut, such as golf balls, this is the ammo's normal diameter.
; Cd : Coeficient of drag. The Cd of a particular ammo is usually dependent on the velocity of the ammo and whether or not it is spinning or tumbling.
; Terminal Velocity : The maximum velocity the ammo will reach when dropped, in air, form a great height.
; Barrel : Suggestions as suitable barrels for the particular ammo. Primarily for ammo that has a defined size, such as a tennis ball.
; Other Info : Various other bits of information concerning the ammo.

'''Table Notes'''
# The Cd values for the various sport balls (tennis ball, golfball ...) were calculated based on their terminal velocities using the equation Cd=2mg/(Aρvterminal2) with g=9.8m/s and ρ=1290g/m3. The terminal velocities were from [http://www.cord.org/uploadedfiles/CTNJune2002.pdf Terminal Velocity Teachers Notes] and [http://www.gantless.com/paper.html A Penny in Free Fall].

{| border="1" cellpadding="5" cellspacing="0" align="left" style="text-align:center"
|+ '''Common Spud Gun Ammo'''
|-
| '''Ammo''' || '''Mass''' || '''Diameter''' || '''Cd''' || '''Terminal Velocity''' || '''Barrel''' ||''' Other Info'''
|-
!colspan="7" align="left" | '''Fruit + Vegetables'''
|-
| half [[Potato]], 2"L || 2.5 oz., 72g || 1.59", 4.04cm || - || - || 1.5" SCH 40 ||align=left|
* density ~1.1g/cm3
|-
| half [[Potato]], 2"L || 5.0 oz., 120g || 2.05", 5.21cm || - || - || 1.5" SCH 40 ||align=left|
* density ~1.1g/cm3
|-
| full [[Potato]], 4"L || 5.1 oz., 140g || 1.59", 4.04cm || - || - || 1.5" SCH 40 ||align=left|
* density ~1.1g/cm3
|-
| full [[Potato]], 4"L || 10 oz., 240g || 2.05", 5.21cm || - || - || 1.5" SCH 40 ||align=left|
* density ~1.1g/cm3
|-
| Apple, || 4.2 oz., 110g || 2.05", 5.21cm || - || - || 2" SCH 40 || align=left|
* density ~0.95g/cm3
|-
| Citrus Fruit, || 3.5 oz., 100g || 2.05", 5.21cm || - || - || 2" SCH 40 ||align=left|
* density ~0.9g/cm3
|-
!colspan="7" align="left" | '''Balls'''
|-
| Ping-Pong Ball || 0.095 oz., 2.7g || 0.95", cm || 0.460 <br\> (note 1) || 9m/s, 30fps || - || -
|-
| [[Golf ball]] || 1.59 oz., 45g || 1.68", 4.27cm || 0.299 <br\> (note 1) || 40m/s, 132fps || - || -
|-
| [[Tennis_ball|Tennis Ball]] || 2.08 oz., 59g || 2.56", 6.5cm || 0.283 <br\> (note 1) || 31m/s, 102fps ||align=left|
* 2.5" SCH 40
* 2.5" SDR 21
* 2.5" SDR 26
|| -
|-
| Baseball || 5.1 oz., 145g || 2.9", 7.4cm || 0.290 (note 1) || 42m/s, 138fps || - || -
|-
| Basketball || 21.2 oz., 600g || 9.5", 24.1cm || 0.500 (note 1) || 20m/s, 66fps || - || -
|-
!colspan="7" align="left" | '''Ball Bearings (BBs, Airsoft, Paintballs...)'''
|-
| 0.177" Copper/Steel BB || 0.0116 oz, 0.33g || 0.177", 0.45cm || - || - || - || -
|-
| 6mm Airsoft || 0.0071 oz., 0.20g || 0.23", 0.6cm || - || - || - || -
|-
| .68" [[Paintball]] || 0.1 oz., 3.2g || ?", ?cm || - || - ||align=left| * 0.5" SDR 13.5 || -
|-
| .61" glass [[marble]] || 0.17 oz., 5g || .61", 1.5cm || - || - || 18mm copper || -
|-
!colspan="7" align="left" | '''Batteries'''
|-
| AA || ? oz., ?g || ?", ?cm || - || - || - || -
|-
| AAA || ? oz., ?g || ?", ?cm || - || - || - || -
|-
| [[C cell|C]] || 2.4-2.6 oz., 68-74g || 0.996", 2.53cm || - || - || - ||align=left|
* 2" (5.1cm) long
* mass varies by brand
|-
| D || ?? oz., ??g || ?", ?cm || - || - || - || -
|-
!colspan="7" align="left" | '''Other Things'''
|-
| [[CO2_cartridge|12g CO2 Cartridge]] (empty) || 1.05 oz., 30g || 0.73", 1.85cm || - || - ||align=left|
* 0.75" SCH 40 PVC
* 22mm Copper pipe
|| -
|-
| [[Ice]] || ?? oz., ??g || ?", ?cm || - || - || - || -
|-
| [[Pycrete]] || ?? oz., ??g || ?", ?cm || - || - || - || -
|-
| Film Canister || 0.5oz., 12g || 1.45", 3.7cm || - || - ||align=left|
*1.25" SCH 40
*40mm 10bar
||* Fits better with the right sized lid, still very good otherwise
|-
| [[Beverage_can|Soda Can]] || 13.0 oz., 369g (water filled) || 2.6", 6.6cm || - || - ||align=left|
* 2.5" SDR 26
* [[Sleeving|Sleeved]] 3" SCH 40
|| -
|}

[[Category:Projectiles]]

Wantedpages

2008-06-14T20:35:26Z

Benstern: made page to help make improving the wiki easier

I am making this as a page to list pages people want to see created. This page separate from the [[Special:Wantedpages|page from the special section]] which shows non-existant pages with links to them. These can either be a result of a wanted page or just bad linking.

==Building materials and construction==
*Threads
*Flange
*Cleanout
*Chamfering
*Teflon tape
*ABS
*Syringe
*Fire extinguishers
*Epoxy

==Accessories and improvments==
*Hop-up
*Suppressors
*Muzzle break
*Propane bottle adapter
*Propane bottle adapter how-to make
*Painting
*Ramrod
*Ballistic pendulum

==Theories==
*Blowby
*Automatic firing
*Semi-automatic firing
*Blowby
*Drag coefficient (CD)
*Cleaning
*Hang-time

==Fuels and related==
*Alcohol
*Hydrogen
*Helium
*Oxygen
*Air
*CO2

==Valves==
*Gate valve
*Globe valve
*Hammer valve

==Tools==
*HCMP
*Launcher Range Calculator
*ProMeterSuite
*SpudTool

==Ammo==
*Airsoft BB
*0.177 BB
*Water

==Other==
*Spudfiles

Muzzle velocity

2008-06-07T01:35:35Z

Benstern: added and fixed links

'''Muzzle velocity''' is the velocity of the projectile immediately after leaving the [[barrel]], and other than a few hypothetical situations, is the fastest the projectile will ever go. Muzzle velocity is typically measured by a [[Chronometer|chronograph]], a device that measures the time it takes the projectile to travel between 2 sensors, although less accurate results can be gathered from a [[ballistic pendulum]] or the quite inaccurate [[hang time]] test.

==Muzzle energy==

This is muzzle velocity's companion, and can be calculated as following:
(1/2)(Mass)(Velocity2), where mass is in kilograms, velocity is in meters/sec, and output is in Joules.
For instance, a 100g (0.1Kg) [[potato]] going 150 meters/sec (a large [[combustion launcher|combustion spud gun]] is capable of this) would have a muzzle energy of:
(1/2)*(0.1Kg)*(150m/s)2=1125 J.

1.5 joules is approximately 1 foot pounds, the traditional imperial (US) unit of energy for firearms.

It should be noted that in the case of [[sabot]]ed projectiles being simulated with the [[GGDT]], the actual muzzle energy is equal to GGDT muzzle energy * projectile mass/projectile mass+sabot mass.

The following is a table of miscellaneous, rim, and centerfire ammunition muzzle energies, for comparison.
<table cell-border=2 cell-padding=1 align=center><tr><td> '''Projectile''' </td><td align=right> '''Energy, J''' </td></tr>
<tr><td>typical [[paintball]]</td><td align=right>17</td></tr>
<tr><td>0.22 rimfire</td><td align=right>180</td></tr>
<tr><td>2" Spud at 300FPS (moderate sized combustion spud gun)</td><td align=right>~400</td></tr>
<tr><td>0.45 colt</td><td align=right>675</td></tr>
<tr><td>410 slug</td><td align=right>1000</td></tr>
<tr><td>2" Spud at 490FPS (large sized combustion spud gun)</td><td align=right>~1100</td></tr>
<tr><td>2" Spud at 600FPS (moderate sized pneumatic spud gun)</td><td align=right>~1600</td></tr>
<tr><td>0.223 (M-16)</td><td align=right>1900</td></tr>
<tr><td>0.60 (M-14, M-60)</td><td align=right>3640</td></tr>
<tr><td>30-06</td><td align=right>4500</td></tr>
<tr><td>100g slug at 1300FPS (moderate sized 10x [[Hybrid Cannon|hybrid spud gun]]) </td><td align=right>~7600</td></tr>
</table>

[[category:Concepts]]

Muzzle loading

2008-06-04T14:27:54Z

Benstern: added and fixed links

The standard way of doing things, because it is the cheapest and easiest to make; in fact, it is not possible to make a launcher that cannot be muzzle-loaded.

To muzzle-load a spudgun:
* Get a (straight) stick, and preferably mark it where it is flush with the muzzle when the pushing end of it is at the desired projectile depth.
* Cut your projectile to size, by either pushing your projectile over your muzzle knife or your separate spud cutter. Paring knifes are not recommended.
* Ram that projectile home. Firm, steady pressure works best. If you cannot get the projectile go down, you may need to scratch it; this is done to allow the air to leak past.

Some design their launchers to be easier to muzzle load by making a small (~1/16") vent hole at the base of their barrel for air to escape. This air would otherwise prevent the nearly airtight [[ammo]] from being rammed down there. Some, however, prefer to install a small [[valve]] of sorts. This prevents air or hot combustion gases from shooting out of the vent hole thus decreasing performance and/or burning the operator.

If you are loading a standard [[Combustion cannon|combustion gun]], the cleanout plug can be removed to prevent pressurization of the [[chamber]] and to avoid the need of any type of vent. For [[Pneumatic cannon|pneumatic launchers]], it is sometimes possible to open a bleed port on the valve to allow the excess air to escape as the projectile is rammed home.

It is recommended that you sharpen your muzzle if you are planning to shoot produce ([[potato|spuds]], zucchinis, etc.). This is called a "muzzle knife" or [[spud cutter]]. If just the outside edge of the muzzle is sharpened, a "single bevel knife", the ammo will be cut so that it's outside diameter is the same as the barrel's inside diameter. The fit will be very nearly air tight. For combustion guns, somewhat better performance can be obtained by adding a small bevel to the inside of the muzzle as well, a "double bevel knife". With a double bevel knife the ammo is cut so that it's diameter is slightly larger then the ID of the barrel. As the ammo is loaded it is compressed giving a very tight fit, very little gas leakage when firing, and increased static friction which is beneficial for combustion guns.

If you do not feel safe having a cutter on the end of your gun, you can instead keep your spud cutter as a separate instrument.

It is generally '''not''' a good idea to load a gun that is otherwise ready to fire. A pneumatic gun should have the ammo loaded before the chamber is pressurized.

Barrel

2008-06-04T14:22:11Z

Benstern: fixed spelling, added links, added 1 more size

The '''barrel''' is the pipe used to launch the projectile, and is, along with the [[chamber]], the only component found in all launchers. The diameter determines what projectiles will fit in the launcher, and the length affects how much energy is transferred to the projectile.

Modifications and improvements to the basic barrel include [[sleeving]], [[rifled barrel|rifling]], [[hop-up]]s and flatline barrels.

There are many diameters of barrels popular in spudding, below are some that fit certain [[ammo]]:

* 4.5mm brakeline - fits bbs, good for [[BBMGs]]
* 6mm brakeline - fits [[airsoft bb]]s, a commonly used ammo in BBMGs.
* 3/4" CPVC, 3/4" sch 80 PVC (looser fit), or 3/4" SCH 120 PVC - fits .68" [[paintball]]s
* 1/2" SCH 40 PVC (.602" id) - fits "AA" batteries, marbles.
* 1/2" SDR 21 PVC (.685" id) - fits .68 caliber paintballs.
* 3/4" SCH 40 PVC (.804" id) - fits 12g [[CO2 cartridge]]s, C batteries.
* 1" SCH 40 PVC (1.029" id) - size [[C cell|"C" batteries]], smaller sized [[bouncy balls]].
* 1.25" SCH 40 PVC (1.360" id) - Fits size [[D cell|"D" batteries]], [[film canister]]s
* 1.5" SCH 40 PVC (1.590" id) - a common size, good trade-off between power and [[potato]] usage. [http://www.spudtech.com/components.asp Available rifled from the [[SGTC]]]
* 1.5" SDR 21 PVC (1.700" id) - fits [[golf ball]]s. Traditionally sleeved within SCH-80 PVC.
* 1.5" SDR 26 PVC (1.734" id)- fits golf balls, but it is thinner than SDR 21, so the golf balls fit a little looser. Traditionally sleeved within 2" SCH-80 PVC.
* 2" SCH 40 PVC (2.047" id) - fits caulk tubes and (large) potatoes.
* 2" SCH 80 PVC (1.913" id) - fits 1.5" nominal pipe well, making it ideal for sleeving Also used as a golf ball barrel by itself, with the golf ball held in place by a rag patch, or other wadding. Also fits normal light bulbs! [http://advancedspuds.com/concreteballs.htm (Details)].
* 2.5" SDR 26 PVC (2.635" id) - fits [[beverage can]]s extremely well
* 2.5" SCH 40 PVC (2.445" id) - fits [[tennis ball]]s well.
* 3" SCH 80 PVC (2.864" id) - fits many drink bottles well.
* 3" SCH 40 PVC (3.042" id) - fits normal [[steel can|cans]], empty propane torch tanks, certain wine bottles, and Gatorade bottles.
* 4" SCH 80 steel (3.826" id) - fits softballs PERFECTLY. Kind of heavy though, at over 15 pounds/foot.
* 4" SCH 40 PVC (3.998" id) - fits 29 oz. cans

Inside diameter (id) data from www.harvel.com
[[Category:Components]]

Tennis ball

2008-06-04T12:51:13Z

Benstern: added and fixed links

'''Tennis balls''' are hollow, pressurized balls of vulcanized rubber, with a fuzzy felt-like covering, approximately 2.6" in diameter. They are sold in many retail stores (including Wal*mart) for use in the game of tennis. 
Somewhat smaller (and significantly cheaper) alternatives with the same basic construction exist, and are marketed as "fun balls" or pet toys.

== Aerodynamics ==

The fuzz on the ball increases air resistance above what would be expected of a sphere, to a Cd of about .6 at high velocities. (See for example this [http://www.aeromech.usyd.edu.au/15afmc/proceedings/papers/AFMC00075.pdf research])

This, coupled with the low sectional density of approx. 10.5g/in2 exterior the launcher, cause the unmodified tennis ball to be a short range projectile; range is limited to about 150 yards (137 meters), even with a powerful launcher.
It should be noted that this is not necessarily a bad thing.

== Modifications ==

The friction required to load a tennis ball in a 2.5" sch 40 barrel is about 12 pounds [http://forums.spudtech.com/topic.asp?TOPIC_ID=14446]. If one finds this excessive, they generally correct the problem by burning the fuzz off.

Additionally, one may seek to increase the range or damage capabilities of the tennis ball. This generally entails weighting the tennis ball by injecting water, or inserting pennies or other small, dense objects. [[Optimal mass]] increase may be calculated with repeated trials using the [[GGDT]]'s integral ''external ballistics calculator''.

== Use and target performance ==

Tennis balls are typically launched out of 2.5" sch 40 pipe, and they may be either [[Muzzle loading|muzzle]] or [[Breech loading|breech loaded]]. Some recommend putting an inside chamfer on the pipe to facilitate loading.

Due to having to reduce the OD of the tennis ball from ~2.6" to 2.445", there is a significant amount of friction; 2.1 - 2.7 [[psi]], average of 2.5 psi, for a force of about 12 pounds (54 newtons). This complicates loading, slightly reduces [[muzzle velocity]], and during launch will scorch the fuzz on the ball.

The inexpensive "fun balls" are slightly smaller, and thus have reduced friction.

As an alternative, some use SDR 21 or 26 2.5", which have IDs of 2.581" and 2.635" respectively.

== Specifications ==

Diameter, unsqueezed: 2.6" (65mm) 
Mass, unfilled: 57g 
Friction; in 2.5" sch 40: 2.5 psi; 12 pounds (.18 k/cm^2; 54 newtons) 

[[Category:Projectiles]]

Cannon construction

2008-06-04T12:44:29Z

Benstern: fixed links

It is important to construct your launchers with care. This includes:

* Using pressure rated (NSF-PW or NSF-61) fittings and pipe, especially in a [[pneumatic cannon]].
* [[Solvent welding]] [http://www.burntlatke.com/weld.html correctly]
* Using pipe of the proper pressure rating, eg. sch 80 in a [[Hybrid Cannon]].
* Only [[tapping|tap]] through a double layer of pipe where the pipe and a fitting is joined (for bolts, [[pressure gauge]]s) .

[[Cell-core]] or [[sleeving|unsleeved]] thinwall [[PVC pipe]] should not be used in the making of cannons. Cellular-core PVC can be used in low-power, [[aerosol]] powered [[combustion cannon]]s, but remember, cellular-core PVC is nothing more than laminated foam.

You may also want to make a design of your cannon first. Sketches and dimensional drawings are both very helpful. You may find out ahead of time that your design will not work, saving precious money. [[3d models]] are some of the most effective visual representations. A limited library of parts (~115) for potato gun construction is currently completed and will be available soon.

See also: [[:Category:Construction materials]], [[:Category:Construction methods]]

{{stub}}

Beverage can

2008-06-04T12:41:54Z

Benstern: fixed links

'''Beverage cans''', also known as '''beer cans''' or '''soda cans''', are disposable aluminum containers sold with a liquid content.
They are easy to fill with water, sand, or concrete.

==Barrels==
Very few pipes fit standard-sized beverage cans; with the only stock pipe being 2.5" SDR 26. Such pipe has a total gap of .035", which is a pretty good fit.

Alternatively, one can make their own [[barrel]] for soda cans, by [[sleeving]] a piece of 3" sch 40 pipe inside another piece of 3" sch 40 pipe using the "modified insert" method.
This yields a barrel with an estimated inside diameter of 2.61" (.01" gap).

Smaller cans, such as those of "energy drinks" are said to fit in 2.5" sch 40 pipe. (Which also fits [[tennis ball]]s)

For those that don't wish to go to the trouble of procuring a special barrel for beverage cans, it's always possible to use a [[sabot]].

==Use and target performance==
Soda cans can be filled with any fluid or solid small-particles including water, sand, or cement. A flap of material can be glued over the opening to keep its new contents inside.
Alternatively, they can be fired without consuming their contents; this effectively spreads the odor of the product.

(Need info on target performance)

Aluminum containers don't biodegrade very well. Pick up your trash.

==Specifications==
* Outside diameter: 2.6 inches
* Length: 4.8"
* Mass: 14 grams
* Wall thickness: .005"
* Volume: 355 ml
* Mass, water filled: 369g

[[Category:projectiles]]

Marble

2008-06-04T12:39:41Z

Benstern: added and fixed links

'''Marbles''' are good solid projectiles, that can penetrate hard targets like wood and sheet metal. They are cheap easy to find and come in a range of sizes, the most common being 1/2", 5/8", 7/8" and 1 inch, or 12, 16, 22 and 25 mm. Larger marbles exist but are often too costly to be used in day to day shooting.

==Use and Target Performance==
The manufacturing tolerances of marbles are often quite wide, so not all 16mm marbles will fit in a 16mm [[barrel]] for instance. If you go to the store to buy marbles, it is suggested to bring a piece of your barrel to test fit your [[ammo]].

A marble hitting a hard target (such as a rock) is often crushed to harmless sand, but there are chances of getting sharp splinters and ricochets, and appropriate care should be taken. Because of their relatively consistent shape and size marbles are good projectiles to use in cannons with automatic loading mechanisms.

==Specifications==
The following sizes are common for marbles both in the US and abroad.
1/2, 5/8, 7/8, or 1" (12, 16, 22, or 25mm)

The average density of glass is ~2.4-2.8 g/ml. This may vary slightly from the density of your marbles, do to manufacturing and glass content differences.

[[Category:Projectiles]]

Launcher configuration

2008-06-04T12:37:01Z

Benstern: added links

== Chamber-Barrel position ==
The possibilities are limitless, but these are the most common ways to position the [[chamber]] and [[barrel]]:

*[[Linear]] or inline
*[[over/under]]
*[[co-axial]]
*[[multiple tanks and T's]]
Like the setup used on the [http://www.spudtech.com/images/products/mega-II-ov2.jpg megah-launcher]. However, the multiple bends results in slightly reduced flow. [[GGDT]] simulations typically don't show much improvement from the increased chamber volume.

== Projectile delivery ==

* [[Muzzle loading]]
The basic option. Projectile loads from the front, and reload time is quite slow. If there's any significant friction between the projectile and barrel, a ramrod must be used to push the projectile down the barrel.

* [[Union]] loading
A step up. Allows you to load the projectile from the breech, but requires alignment and twisting afterwards. A union can also hold a [[burst disk]]. [[Camlock coupling]]s are similar to unions, but faster to open and close. They are usually rated for less [[pressure]] than unions.

* [[Breech loading]]
Allows you to load a projectile from the breech (end of gun towards user). Mechanism and loading time varies by construction technique.

* [[Vogt-pattern]]
A tube holds the [[ammo]], about around half a dozen balls. Upon firing, the balls are sucked one-by-one into the airflow, resulting in a tight grouping of balls fired a few dozen milliseconds apart. Suitable for large-caliber weaponry (has been tested with as large as [http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=11012 tennis balls]) Named after the late [[Bill Vogt]], who came up with the design.

[[category:Concepts]]

Index

2008-06-04T10:23:43Z

Benstern: fixed links

This page is under construction, but should provide an '''alphabetical''' list of common spudding terms, as well as a note/definition about the term.

If you feel like it, start adding things.

==A==
ABS (Acrylonitrile Butadiene Styrene) - A plastic used in plumbing applications. More resistant to shock, low temperature, and chemicals, but difficult to find rated for pressure. Pressure rated ABS is legal for compressed gas applications.

==B==

Ballistics - The science of the motion of projectiles. Sometime divided into two sub-classes; "Internal Ballistics" is the motion of the projectile while it is still in the barrel, "External Ballistics" is the motion of the projectile after it has left the barrel.

[[Barrel]] - Present on all cannons. A barrel is a tube designed to allow the projectile to reach maximum velocity before the pressurized gas propelling it escapes to the atmosphere. Barrels also improve accuracy, and can be rifled to improve accuracy further.

BBMG - See [[BB machine gun]].

[[BB Machine Gun]] - Pneumatic gun designed to fire airsoft pellets or metal BBs at high rates of fire.

Bottled Gas - See [[Gas bottle]]

[[Butane]] - A common fuel for combustion spud guns. Butane, a gas at room termperature and pressure, is readily available in disposable lighters.

==C==
[[Chamber]] - An element shared by all pressure based cannons, where either the pre-compressed air or flammable gas mixture is stored before firing.

[[Chronometer]] - 1. A device for measuring time. 2. A device for measuring the muzzle velocity of a gun. See also Chrony, muzzle velocity.

Chrony - A commercial device for measuring the muzzle velocity of a gun. Used for "real" guns, paintball guns, bows, and spud guns.

[[Combustion Cannon]] - A cannon that generates pressure by burning flammable gases.

[[Compressor]] - Motorized air pump.

[[Copper]] - Metal. Construction material.

==D==
[[DDT]] - Deflagration to Detonation Transistion. This very dangerous effect occurs when the flame front in a combustible gas mix exceeds the speed of sound in the gas - creating a super sonic shockwave and a very large pressure spike which may damage or destroy the [[chamber]].
It is very rare, and is only likely to occur in high mix [[Hybrid cannon]]s, or in combustion cannons with very long chambers.

[[Diaphragm valve]] - Related to [[Piston valve]]. Generally rarer, but often considered to open faster but have lower flow. Typically used in coaxial designs, and commercially manufactured as inline sprinkler valves.

Drain Waste Vent (DWV) - A designation by the NSF (National Sanitation Foundation) that means the item is approved for drain, waste, or venting applications. By nature, DWV does not require a pressure rating, but some DWV pipes are rated for pressure.

==E==
[[Epoxy]] - A combination of chemicals that form a bond much stronger than any glue. Often used for sealing leaks or during sprinkler valve modification. Some people have created very large parts of cannons from epoxy, as well as pistons.

==F==
Flame Front - The edge of a flame whose speed, in part, affects the power of the cannon it is powering. If the flame front exceeds the speed of sound, [[DDT]] occurs.

==G==
[[Gas Bottle]] - A metal cylinder filled with pressurized gases.

==H==
[[Hybrid Cannon]] - A cannon that uses a pre-compressed flammable gas mixture. The increased fuel + oxygen charge in the chamber substantially increases the pressure, temperature and energy in the chamber. Ignition is somewhat difficult, as spark length is roughly inversely proportional to pressure. Very powerful, but requires experience to successfully and safely implement.

==I==

[[Ignition source]] - Used to start the combustion reaction in a [[combustion cannon]] or [[Hybrid Cannon]]. Sources range from lantern sparkers, to piezoelectric grill ignitors, to ignition coils and camera flash circuits.

==J==

==K==

==L==
Lathe -

==M==

Mach - The speed of sound for a ''given set of environmental conditions''. The speed of sound changes with temperature and the nature of the fluid involved. For dry air at 15C, one Mach is equivalent to 340.3 m/s (1225 km/h, 761.2 mph, 1116 fps). At normal temperatures the small temperature dependence is usually ignored. At the elevated temperatures that exist in the chamber of a combustion gun, the speed of sound is significantly increased. At the adiabatic flame temperature of propane in air the speed of sound is increased by about 3-fold to ~990 m/s (3560 km/h, 2210 mph, 3250 fps).

MAPP - A bottled gas used in combustion or hybrid applications. MAPP has been experimentally determined to produce muzzle velocities 11% greater than those of propane.

Muzzle Knife - (Aka [[spud cutter]].) The sharpening of the muzzle of a barrel so that it will automatically cut a spud to the proper size for the barrel. Internal beveling of the muzzle can produce a better seal. See also [[spud cutter]].

==N==
Nitrogen - An inert gas with a lower molar mass than the average of air. This allows slightly higher particle speeds, and therefore, higher muzzle velocities.

NSF - National Sanitation Foundation. "NSF" is often printed on pipe, along with letters that designate what applications the pipe is NSF-approved for.

==O==
O-Ring - Often made of Neoprene or similar, these rings can seal thousands of pounds of pressure, but must be mounted very precisely for most applications, which often requires use of a lathe.

==P==
Piezoelectricity - A property of certain materials where the material can be mechanically stressed, and produce high voltage electric current. When electricity is applied to the crystal, it vibrates. This property is implemented in grill ignitors, which are commonly used as ignition sources in spud guns.

Pilot Valve - A valve whose purpose is to exhaust pilot air, thus triggering a larger main valve, or, in cases, another pilot valve.

[[Piston valve]] - A high power home-made valve which is generally considered to be second only to [[Burst disk]] valves in performance, but more practical to use. Releases air by rapidly exhausting the area behind the piston (pilot), thus causing the piston to be pushed backwards, and stop sealing the chamber from the barrel. See also: [[Diaphragm valve]]

[[Pneumatic Cannon]] - A cannon that uses pre-compressed air for power.

Potable Water (PW) - An NSF designation found on some plumbing pipe and fittings. Potable Water systems are pressurized, so, by nature, NSF-PW pipes are pressure rated.

[[Propane]] - A common fuel for combustion spud guns, as well as hybrid cannons.

[[PVC]] - Most common spudgun construction material. Gets brittle in cold weather, and may shatter if dropped or abused. Pressure rated PVC is easy to find in the U.S., although large diameter pipe is difficult to find. PVC is illegal for compressed gas applications.

==Q==
[[QEV]] - Quick Exhaust Valve. Essentially a pre-made [[piston valve|piston]] or [[diaphragm valve]]. These are quite hard to find, and are moderately expensive.

==R==

==S==

[[Safety]] - More important than even the spudgun. If you don't have this, then you need it fast.

Schelkin Spiral - A method that causes turbulence in burning gasses. This increases the risk of [[DDT]].

[[Spark_gap|Spark Gap]] - A spark gap consists of two metal electrodes placed close to each other with a gap in between, where an electrical spark can jump. They are used for igniting the fuel in combustion and hybrid cannons. Electrodes that are more pointed can generate a longer spark at a given voltage than those that are more planar.

==T==
Tee - A name for pipe fittings that have sockets arranged so that the fitting looks like the letter "T".
==U==

==V==
[[Valve]] - Essential to pneumatic cannons. A valve retains pressure and then opens, or in the case of a burst disk, ruptures, to release the air. A valve will perform better if its flow rate is increased, or its opening speed is decreased.

[[Vortex cap]] - Typically a cap in shape and is made out of strong materials such as PVC or metal. Their construction is similar to the Vortex Block, in which an air inlet and a hole for a barrel are drilled perpendicular to each other. The vortex cap was designed by Davidvaini and provides a small substitute to the standard vortex or inline vortex blocks.

==W==
Wye - A name for pipe fittings that have sockets arranged so that the fitting looks like the letter "Y".

==X==

==Y==

==Z==

Venting

2008-06-04T10:18:47Z

Benstern: added category: concepts

Venting is the action of cleaning out combustion products and introducing fresh air to the [[chamber]] of a [[combustion cannon|combustion]] or [[hybrid cannon]]. This is necessary to ensure that there is enough oxygen present to sustain the combustion of the [[fuel]].

Venting can be done by simply opening the chamber by means of a threaded plug or cap, a large [[ball valve]], or a [[check valve]]; a [[chamber fan]] is often used to help exchange the gases. Other venting methods include using a bike pump, [[compressor]] or [[mattress inflator]] to inject air into the chamber. Pressurized air from a scuba or HPA paintball tank can also be used, but with a [[pressure regulator]].

[[Category:Concepts]]

DDT

2008-06-04T10:11:05Z

Benstern: moved to category concepts

"DDT" stands for Deflagration to Detonation Transition and is the technical term for the little-understood phenomenon that occurs when the flame front inside a burning fuel/air mixture reaches and exceeds the (local) speed of sound. Note that the speed of sound changes with pressure, temperature, and even humidity, so the speed of sound inside the combustion chamber can be very different from the atmospheric speed of sound.

In a normal combustion situation, the flame front in a burning fuel/air mixture does not exceed the speed of sound, classifying it as a deflagration (see [http://en.wikipedia.org/wiki/Deflagration Deflagration on Wikipedia]). The combustion inside a gasoline or diesel engine, gunpowder, and low-grade explosives are all deflagrations.

Under rare circumstances (generally in respectively long, thin combustion chambers containing pressurized fuel/oxidizer mixtures), the flame front can exceed the (local) speed of sound, as does the flame front of high explosives, classifying it as a [http://en.wikipedia.org/wiki/Detonation Detonation]. This transition from subsonic to supersonic can create an immense pressure spike that has damaged even well-constructed metal chambers, and is certain to cause a PVC chamber to fail. Usually pipe will fail at the point where DDT happens. This is because the point is subject to a localized rapid high pressure change.

It is the goal of anyone who constructs a [[hybrid]] launcher to avoid DDT. It is thought that a short, fat (theoretically closer to spherical) chamber is less likely to incur DDT than a long, thin chamber. Using oxygen enriched mixtures or exotic fuels such as acetylene increase the risk of DDT.

Here we can see the first normal pressure spike at 2510 µsec compressed the fuel and air and caused a DDT at 2555 µsec.

[[Image:6_6.gif]]

For more information on DDT, try [http://www.google.com/search?hl=en&q=deflagration+detonation+transition&btnG=Search Google]

[http://www.gexcon.com/index.php?src=handbook/GEXHBchap6.htm#sect6.3 GexCon article on DDT]

[[Category:Concepts]]

Chronometer

2008-06-04T10:07:46Z

Benstern: moved to newly created Tools category

In the world of devices that launch things at high velocity a '''chronometer''' is a device for measuring a projectile's velocity. This device is sometimes referred to as a "'''shooting chronometer'''".

There are many methods for measuring the speed of a projectile. They range from simply counting how long a round takes to hit the ground after being fired straight up (the "hang time" method) to sophisticated commercial devices that can measure velocities to an accuracy of a couple percent over a range of velocities from a few tens of feet per second (FPS) to several thousand FPS.

== Hang Time Method ==

One method for estimating the [[muzzle velocity]] of a spud gun is to measure the hang time for a spud fired straight up. The "hang time" is the time from when the spud leaves the [[barrel]] until it hits the ground. If there is no air friction, then the speed at which the spud hits the ground is the same as the muzzle velocity. If air friction is neglected, the formula is based on the equation of motion in a uniform gravitational field;

''Muzzle velocity = (1/2)gt''

Where ''g'' is the acceleration due to gravity (32.2 fpss, 9.81m/s) and ''t'' is the time in seconds from firing until the round hits the ground. So, a hang time of 10 seconds would suggest a muzzle velocity of (1/2)(32.2fpss)(10s)=161fps.

Unfortunately, for a typical spud gun, air friction is significant and makes the simple calculation fail miserably. Hang time can be used to estimate the relative muzzle velocity of two guns firing the same [[ammo]] but it can not be used to calculate the actual muzzle velocity.

If the aerodynamic characteristics of the ammo are known then the hang time can be used to estimate the muzzle velocity, such as in the case of a tennis ball, whose Cd (Coefficient of Drag) has been experimentally determined to be about 0.6.

== Commercial Shooting Chronometers ==

There are several commercially available chronometers suitable for use with spud guns. Perhaps the most common is the Chrony® F1, a product of [http://www.shootingchrony.com/ Shooting Chrony Inc.] The F1 sells at retail for $90 and they are frequently available used for a bit less.

The F1 uses optical detectors to detect the passage of the round and the velocity is shown on a digital display.

== PC and Laptop Based Homemade Chronometers ==

It is fairly easy to construct a usable shooting chronometer from readily available parts. If you have access to a PC or laptop then a chronometer is trivial to construct. The PC can be just about any old PC that has a Win98 or later (or about any version of a Mac) operating system. An old PC that has been retired makes an excellent "data acquisition system" for a homemade chronometer.

Since most guns operate in the subsonic to supersonic range any device designed to work with audio signals will have suitable characteristics.

Most PCs and Laptops made in the last 15 years came equipped with a sound card. The sound card is an analog to digital (A/D) and digital to analog (D/A) converter. Sound cards are usually dual channel (left and right stereo channels), sample at up to 48,000 (48KHz) samples per second at 8 or 16 bits resolution per sample. Therefore, the typical sound card is a fairly powerful data acquisition system. It is possible to buy better data acquisition systems (i.e., laboratory grade equipment) but they are expensive. For our purposes, the sound card is more than adequate and readily available.

== Sound Based Homemade Chronometer ==

The simplest way to use the sound card as a chronometer is to just use a microphone to record the sound of the gun firing at a solid target. The audio recording will have a signal at the moment the projectile left the barrel and another when it strikes the target. If the microphone is positioned the same distance from the muzzle and the target then the average velocity of the round is simply the distance from the muzzle to the target divided by the flight time. If the target is reasonably close to the muzzle, within say a few feet, then the average velocity is essentially the same as the muzzle velocity.

There are a couple software packages that are of use in a PC audio based chronometer. [http://audacity.sourceforge.net Audacity] is an excellent freeware sound recording, visualization and analysis package. Audacity can be used to both record the audio and measure the flight time.

[http://talonairgun.com/softchrono/ SoftChrono] is a freeware Windows application specifically designed for using a microphone plus soundcard as a shooting chronometer.

== Optical Input to a Sound Card Based Chronometer ==

Recordings that are somewhat simpler to interpret can be made if the microphone is replaced with a pair of optical detectors such as phototransistors. This optical approach eliminates any possible confusion caused by echoes and gives a signal that is much easier to interpret.

For example, using the setup described [http://www.inpharmix.com/jps/Jims_chrono.html here], the recording below was obtained for the firing of a [[BB machine gun]];
[[Image:long_burst_part.jpg]]

Each pair of peaks represents a single BB passing over the two photo detector gates. The gates were three inches apart and the first gate an inch or two from the gun's muzzle. The velocity of each BB is calculated as the time between peaks (in seconds) divided by the distance between the two gates. Based on this recording, this particular BBMG is firing at about 330 FPS (the velocity varies from round to round) and with a rate of fire of ~4800 rounds per minute.

[[Category:Tools]]

Compressor

2008-06-04T10:06:51Z

Benstern: created and added category: Tools

A '''compressor''' is a mechanical pump that compresses gas. They range from small 12 Volt emergency compressors with relatively high [[pressure]] but very low volume, to shop compressors with large air tanks for storage, and scuba compressors that can deliver thousands of [[psi]] to fill high pressure cylinders.

== Pros/Cons of each type ==
'''12 Volt Emergency Compressor:'''

''Advantages:''
* Quite cheap to buy
* Light
* Theoretically capable of 200-300 psi

''Disadvantages:''
* Low flow
* Poor duty cycle - as low as 20% (the other 80% is for rest) is not uncommon.
* Prone to malfunction and often have a very short life.
* Requires power source (Car battery, car battery charger, or Mains to cigarette socket transformer)
* Noisy

'''Tool/Shop Compressor:'''

''Advantages:''
* Reasonably cheap to run
* Fast.
* Won't run out, unlike [[gas bottle]]s.
* Can provide a mobile pressure supply if gasoline powered.

''Disadvantages:''
* Requires power socket (if electrical).
* Requires fuel (if [[gasoline]] powered).
* Heavy.
* Typically limited to 8 bar/120 psi but 10 bar/145 psi types are available.
* Can be costly to buy initially.
* Noisy

'''Scuba Compressor'''

''Advantages:''
* Very high pressure (typically 2500-4500 psi)
* Can be used to fill gas bottles.
* Moderate flow

''Disadvantages:''
* Very large.
* Very expensive.
* Noisy.
* Power socket required.

==Types of compressors==
*'''Reciprocating''' - Uses a reciprocating piston to draw gas in through a [[valve]] and force the drawn gas into a storage tank or through a smaller orifice. They are available with single or multiple cylinders, depending upon the pressure and volume required. Reciprocating compressors are referred to as positive displacement compressors. (1)
*'''Rotary Screw''' - Two intermeshing helical rotors in a twin bore case are used to compress between one convex and one concave rotor. The trapped volume of gas is decreased while the pressure is increased. Rotary screw compressors are referred to as positive displacement compressors. (1)
*'''Centrifugal Compressor''' - Unlike the reciprocating and rotary screw compressors, centrifugal compressors do not make use of positive displacement. Gas enters the center of rotation of an element and is forced outward. The element can use curved blades, radial blades, or backward blades. The acceleration of the gas causes the pressure to rise. (1)

sources:
(1) http://www.ctrlsys.com/library/applications/compressors-2.php

[[Category:Tools]]

Talk:Cloud BBMG

2008-06-04T10:05:43Z

Benstern:

Is it random movement of the BBs or the Venturi effect at work to suck BBs into the barrel?

Cloud BBMG

2008-06-04T10:04:25Z

Benstern: added category bb machine gun

A '''cloud chamber [[BB machine gun]]''', or BBMG, works by blowing air up through a mass of BBs (BBs are small plastic or metal balls). This makes a "cloud" of BBs inside the [[chamber]] in which the BBs move around at random, and occasionally get near enough to the entrance to the [[barrel]] to be sucked in.

The actual cloud chamber is typically built within a short length of small diameter pipe, such as a couple inch segment of 1.25" sch 40 pipe. More detailed descriptions can be found [http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=11115 here]
However, cloud chamber launchers [http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=8085 have been built] to accept [[ammo]] up to 3/4" projectiles.

A cloud chamber BBMG typically gets rates of fire of about 50 projectiles per second, which is at least as good as the [[vortex block]] style of construction.

[[Category:BB machine gun]]

Chronometer

2008-06-04T10:02:00Z

Benstern: added to category Accessories

Mauler Valve

2008-06-04T09:57:24Z

Benstern: added link

The Mauler valve is a commercially available [[barrel]] sealing [[piston valve]] for the use in [[pneumatic cannon]], designed by Sean Gort.

An independent test by John Shell, author of [http://neospud.com/ NeoSpud], found that the Mauler valve yields [[muzzle velocity]] superior to that of the [[Supah-Valve]]. A [[chronometer|shooting chronograph]] was used to return muzzle velocity data.

The Mauler valve is unique in that it utilizes modified [[PVC pipe]], and fittings. In contrast the Supah-Valve has machined PVC bar stock for the internal components. Both [[valve]]s use a lathe to modify the components found in the valve. The Mauler using a wood lathe, and the Supah-Valve using a metal lathe. The difference between the wood, and metal lathe is how the tooling is controlled. On a metal lathe, the tooling is fixed in a mechanism, then moved along linear axises. With a wood lathe the tooling is held in the operators hands, steadied by a tool rest.

'''Specifications:'''
* 2" Female NPT Porting
* Encased in 2.5" PVC [[tee]]

==Variants:==
For every size variation the valve is given a different name.

'''NPT Porting:'''
* 1.5" - Shredder
* 1.25" - Ripper
* 1" - Stinger

[[category:valves]]

CALM

2008-06-04T09:53:46Z

Benstern: added links

Compressed Air Launcher Modeling Program

by AKBiocca comcast net

The CALM modeling software works by computing the amount of air that passes
through the [[valve]] every 100 microseconds, subtracting the from the
[[chamber|pressure chamber]] and adding it to the [[barrel|bore]]. The force on the ([[tennis ball]])
Projectile is computed, the net acceleration, velocity, and new position.
New [[pressure]]s are computed for the bore and chamber. This is repeated
until the ball leaves the bore. This allows us to see what is
happening in some detail.

The CALM program is written in the Python language, and is available in source code
format, so you can see how it works and even make changes.

CALM is available at http://www.qsl.net/wb6zqz/calm.html

CALM Example

example launcher webpage at: http://www.qsl.net/wb6zqz/csv19/index.html

<pre>
Computer Modeled Launcher Performance*

CSV-19 Compact Sprinkler Valve 19 inch Launcher

16" SDR21 2.5" Barrel, 8" by 4" Schedule 40 PVC Chamber,
Rainbird 1" Sprinkler Valve, Over/Under configuration

system Cv 5.0 Ballwt 4.0 ounces

chp oal chl bbl fps sec xbp xcp ht tofl

30 19 8 14 79 0.020 0.2 20.5 76 4.4
40 19 8 14 105 0.017 1.3 29.7 117 5.4
50 19 8 14 123 0.015 2.5 38.8 146 6.0
60 19 8 14 138 0.014 3.7 48.0 168 6.5
70 19 8 14 151 0.013 4.8 57.1 188 6.9
80 19 8 14 162 0.013 5.9 66.3 205 7.2

Cv = system flow coefficient, gpm per psi
chp = chamber pressure in psi
oal = overall length inches
chl = chamber length
bbl = barrel length
fps = velocity feet per second
sec = barrel time in seconds
xbp = exit bore pressure
xcp = exit chamber pressure
ht = peak trajectory height in feet
tofl = time of flight in seconds

* note that these performance numbers are uncalibrated and subject to change
based on measurements with your own launcher. The Cv value can be adjusted to
fit your specific results. They seem to be quite close to the Dacron line
measurement, however measurements with new synthetic line were somewhat higher.
</pre>

[[category:Concepts]]

Steel Pipe

2008-06-04T09:50:09Z

Benstern: added links and fixed spelling

'''Steel''' pipe comes in many flavors (Galvanized, stainless, etc), and is a good choice for the construction of a spudgun.

Advantages and disadvantages of steel pipe:

'''Advantages:'''

-Readily available at many hardware stores.

-Rated for [[pressure]] (Full details can be found at [http://www.engineeringtoolbox.com/wrought-steel-pipe-bursting-pressure-d_1123.html Here])

-Threaded fittings

-Cheap, relative to [[Copper pipe|copper]]. It is also available in larger diameters.

-Durable

-Will not melt (but it will heat up!).

'''Disadvantages:'''

-Heavy

-Length of pipe cannot be changed, if threaded fittings are used.

-More difficult to drill into/[[Tapping|tap]] threads than PVC.

[[Category:Construction materials]]

Gasoline

2008-06-04T09:45:55Z

Benstern: added links, fixed spelling

==Use as a Fuel==

Gasoline is used in some [[combustion cannon]]s. It can be [[Fuel meter|metered]] like [[propane]], but instead using a syringe. Gasoline provides a powerful [[Combustion process|combustion]], but will very easily flood the [[chamber]].

==Myths==
Gasoline will not damage PVC chambers as proved in a [http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=7896 test] by a well-respected Spudtech forum member Plasticex009.

==Safety==

An excessive amount of gasoline in a combustion launcher will not fragment a properly constructed chamber, but can drip out, causing burns to the operator and fire hazard. A surprisingly small amount of gasoline (about 0.12ml per liter of chamber volume) is necessary for proper combustion.

[[Category:Fuels]]

Flow coefficient

2008-06-04T09:42:33Z

Benstern: added links, added to Stubs category

The flow coefficient of a [[valve]] is a relative measure of its efficacy at allowing fluid flow. It describes the relationship between the [[pressure]] drop across an orifice and the corresponding flow rate.

[[category:Concepts]]
[[category:Stubs]]

Cell-core

2008-06-04T09:40:51Z

Benstern: added links

Cellular core pipe is basically hard foam with a veneer of plastic on the outside and inside. It is commonly used for DWV (drain, waste, vent), and is not rated for [[pressure]]. Do '''not''' use it for [[pneumatic cannon]]s.
It can usually withstand the limited pressures created by a [[combustion cannon]], but it is not recommended due to the fact that it is non-pressure rated pipe. It will have "cellular core - not for pressure" written on it, and probably DWV.
[[Category:Construction materials]]

Bushing

2008-06-04T09:37:45Z

Benstern: added links

Used for connecting two pipes of different sizes. This is different then a reducer in the respects that a reducer connects two male pieces, meanwhile a bushing connects both a female and male pipe. The larger side is for inserting into female connections and the smaller side connects to male connections.

Often used to connected the [[barrel]] to the [[chamber]] and doesn't angle on the outside but rather the inside. Most commonly the bushing is inserted into a coupling, but will connect to any female connection that is both the same size and connection type (Slip or Thread).

Some people [[bushing modification|modify]] them so that the stop on the inside of it is no longer present.

[[category:Fittings]]

Common Fuels for Combustion Spudguns

2008-06-04T06:37:27Z

Benstern: added links

So, you've glued together some hunks of PVC, installed an [[Ignition source|ignition
system]] and bought a bag of [[potato|russets]]. What should you use for [[fuel]] to get
the most oomph into
that hunk of starch? There are many ways to judge the best fuel for a
[[Combustion cannon|combustion spud gun]]. How
easy is it to use? How expensive is it? And, perhaps most important to
the average spudder, which fuel
will launch the spud at the highest speed?

=You Must Use The Correct Amount Of Fuel=
Before discussing the various fuel options we'll start with the most important aspect of fueling a combustion spudgun.

'''You Must Use The Correct Amount Of Fuel'''.

An inexperienced spud gunner might think that adding more fuel to the [[chamber]] will increase the power of their gun. This is almost always incorrect. For all common fuels too much fuel won't ignite. All fuels have a property called the "combustion limits". The combustion limits is the range of fuel concentration (usually expressed as the volume percent of fuel in the chamber) that will actually ignite. For most hydrocarbon fuels ([[propane]], [[butane]], flammable [[aerosol]]s etc.) the combustion limits is about 3% to 9% by volume. If you inject less than ~3%, or more than ~9% of the chamber volume in fuel then the gun will not ignite.

'''If you've built a combustion spudgun and you can't get it to fire the most likely problem is that you are using too much fuel.'''

So, your first challenge is to get your fuel in the 3~9% range so that the gun will fire. Your second challenge is to try to get the fuel as close as possible to the '''stoichiometric''' fuel ratio. The [[Stoichiometry|stoichiometric]] fuel ratio is the ratio of fuel to oxygen that allows all the fuel to burn and leaves no oxygen left over at the end of [[Combustion process|combustion]]. The stoichiometric fuel ratio will get you very close to the maximum power the fuel is capable of.

The stoichiometry is determined by the fuel you are using. For example, the balanced chemical equation for the complete combustion of propane (C3H8) in air (~21% oxygen, O2) is;
C3H8 + 5O2 = 3CO2 + 4H20

For every molecule of propane we need 5 molecules of oxygen. Combustion produces 3 molecules of carbon dioxide (CO2) and 4 molecules of water. Gases have the handy property that the number of molecules is proportional to the volume at a constant [[pressure]] so the volume ratio of fuel to air will be the same as the ratio of molecules. Since air is only ~21% oxygen we can calculate that for every unit of volume of the chamber we need (1C3H8/5O2)*(0.21) = 0.042 volumes of fuel. 0.042 volumes of fuel is the same as 4.2% of fuel. (There are some subtleties about calculating the actual volume percent that'll be discussed below.)

=Common Fuels for Combustion Spud Guns=
<h2>Heats of Combustion</h2>
The "heat of combustion" of a fuel
is a measure of the amount of energy
released when the fuel is
burned. This is an important, but not the only, factor affecting the
performance of a fuel. The table
below lists the heats of combustion along with other parameters for a
variety of pure fuels. 
 
Heats of combustion can be measured in several different ways and this
makes it difficult to find a consistent set of values for various
fuels. Web based sources list both "high heat" values (which are
obtained assuming the water produced condenses to liquid) and "low
heat" values (which assume the water is present as steam) as well as
thermodynamic heats of combustion. For this reason, the table below
lists multiple values for most of the fuels. To obtain a consistent set
of values for comparison purposes, I have used the red ones which were calculated
using the method at [http://home.fuse.net/clymer/rq]. 
 
The "Displasive Volume Percent" column gives the stoichiometric volume
of fuel required if the fuel displaces some of the air in
the chamber when it is injected, for example when fueling with the
"squirt and screw" method or using a syringe. The "Additive Volume
Percent" gives the amount of fuel
required when the fuel does not
displace air from the chamber, for example when using a [[Fuel meter|pressurized
meter system]]. 
 
The key value for comparing two fuels based on their heats of
combustion is not the actual heats of combustion. Instead, the "Heat
per mole Oxygen" should be used since the amount of energy in the
combustion chamber is
limited by the amount of oxygen present in the chamber. Fuel is added
to match that amount
of oxygen. As you can see from the table, there is relatively little
difference between the various fuels based on their "Heat per mole
Oxygen" values. The only two fuels with significantly higher values are
hydrogen and [[acetylene]], both of
which give 10~15% more energy
than the other fuels.
<table border="1" cellpadding="1" cellspacing="0">
<tr>
<td align="center" valign="middle"> Fuel</td>
<td align="center" valign="middle">Heat of Combust.
(Kcal/mole)</td>
<td align="center" valign="middle">Combustion Limits in
Air (Vol%)</td>
<td align="center" valign="middle">Boiling Point,C (F)</td>
<td align="center" valign="middle">Mole O2
per mole Fuel</td>
<td align="center" valign="middle">Heat per mole Oxygen
(Kcal)</td>
<td align="center" valign="middle">Displasive Volume
Percent(1)</td>
<td align="center" valign="middle">Additive Volume
Percent(1)</td>
<td align="center" valign="middle">Molecular Weight
(g/mol)</td>
<td align="center" valign="middle">Combustion Equation</td>
</tr>
<tr>
<td align="center" valign="middle"> Hydrogen</td>
<td align="center" valign="middle">68.3 
62.5 
59.7</td>
<td align="center" valign="middle">4.0 - 74.2</td>
<td align="center" valign="middle">-253 
(-423)</td>
<td align="center" valign="middle">0.5</td>
<td align="center" valign="middle"> 
119</td>
<td align="center" valign="middle">29.5</td>
<td align="center" valign="middle">41.9</td>
<td align="center" valign="middle">2</td>
<td align="left" nowrap="nowrap" valign="middle"> 2H2 +
O2 = 2H20</td>
</tr>
<tr>
<td align="center" valign="middle"> Methane</td>
<td align="center" valign="middle">192 
191 
212 
215</td>
<td align="center" valign="middle">5 - 15</td>
<td align="center" valign="middle">-162 
(-259)</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">108</td>
<td align="center" valign="middle">9.48</td>
<td align="center" valign="middle">10.5</td>
<td align="center" valign="middle">15</td>
<td align="left" nowrap="nowrap" valign="middle"> CH4 +
2O2 = CO2 + 2H20</td>
</tr>
<tr>
<td align="center" valign="middle">Ethane</td>
<td align="center" valign="middle">373 
340 
371</td>
<td align="center" valign="middle">3 - 12.5</td>
<td align="center" valign="middle">-89 
(-184)</td>
<td align="center" valign="middle">3.5</td>
<td align="center" valign="middle">106</td>
<td align="center" valign="middle">5.65</td>
<td align="center" valign="middle">5.99</td>
<td align="center" valign="middle">30</td>
<td align="left" nowrap="nowrap" valign="middle"> 2C2H6
+ 7O2 = 4CO2 + 6H20</td>
</tr>
<tr>
<td align="center" valign="middle">Ethylene 
(Ethene)</td>
<td align="center" valign="middle">315 
337 
337</td>
<td align="center" valign="middle">2.8 - 28.6</td>
<td align="center" valign="middle">-103.7 
(-155)</td>
<td align="center" valign="middle">3</td>
<td align="center" valign="middle">112</td>
<td align="center" valign="middle">6.53</td>
<td align="center" valign="middle">6.98</td>
<td align="center" valign="middle">28</td>
<td align="left" nowrap="nowrap" valign="middle"> C2H4
+ 3O2 = 2CO2 + 2H20</td>
</tr>
<tr>
<td align="center" valign="middle">Acetylene</td>
<td align="center" valign="middle">322 
301</td>
<td align="center" valign="middle">2.5 - 80 </td>
<td align="center" valign="middle">-81 
(-119)</td>
<td align="center" valign="middle">2.5</td>
<td align="center" valign="middle">120</td>
<td align="center" valign="middle">7.73</td>
<td align="center" valign="middle">8.38</td>
<td align="center" valign="middle">26</td>
<td align="left" nowrap="nowrap" valign="middle"> 2C2H2
+ 5O2 = 4CO2 + 2H20</td>
</tr>
<tr>
<td align="center" valign="middle"> Propane</td>
<td align="center" valign="middle">525 
487 
530 
527</td>
<td align="center" valign="middle">2.37 - 9.5</td>
<td align="center" valign="middle">-42.1 
(-44)</td>
<td align="center" valign="middle">5</td>
<td align="center" valign="middle">105</td>
<td align="center" valign="middle">4.02</td>
<td align="center" valign="middle">4.19</td>
<td align="center" valign="middle">44</td>
<td align="left" nowrap="nowrap" valign="middle"> C3H8
+ 5O2 = 3CO2 + 4H20</td>
</tr>
<tr>
<td align="center" valign="middle"> Butane</td>
<td align="center" valign="middle">684 
633 
687 
683</td>
<td align="center" valign="middle">1.86 - 8.41</td>
<td align="center" valign="middle">-0.5 
(31)</td>
<td align="center" valign="middle">6.5</td>
<td align="center" valign="middle">105</td>
<td align="center" valign="middle">3.67</td>
<td align="center" valign="middle">3.81</td>
<td align="center" valign="middle">58</td>
<td align="left" nowrap="nowrap" valign="middle"> 2C4H10
+ 13O2 = 8CO2 + 10H20</td>
</tr>
<tr>
<td align="center" valign="middle">iso- Butane</td>
<td align="center" valign="middle">683</td>
<td align="center" valign="middle">1.86 - 8.41</td>
<td align="center" valign="middle">-11.7 
(11)</td>
<td align="center" valign="middle">6.5</td>
<td align="center" valign="middle">105</td>
<td align="center" valign="middle">3.67</td>
<td align="center" valign="middle">3.81</td>
<td align="center" valign="middle">58</td>
<td align="left" nowrap="nowrap" valign="middle"> 2C4H10
+ 13O2 = 8CO2 + 10H20</td>
</tr>
<tr>
<td align="left" bgcolor="#dddddd" valign="middle"> [[MAPP]](2)</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
<td bgcolor="#dddddd"> 
</td>
</tr>
<tr>
<td align="center" bgcolor="#dddddd" valign="middle">Methyl Acetylene</td>
<td align="center" bgcolor="#dddddd" valign="middle"> 
</td>
<td align="center" bgcolor="#dddddd" valign="middle"> 
</td>
<td align="center" bgcolor="#dddddd" valign="middle">-23.2 
(-9.0)</td>
<td align="center" bgcolor="#dddddd" valign="middle">4 </td>
<td align="center" bgcolor="#dddddd" valign="middle"> 
</td>
<td align="center" bgcolor="#dddddd" valign="middle">4.98</td>
<td align="center" bgcolor="#dddddd" valign="middle">5.24</td>
<td align="center" bgcolor="#dddddd" valign="middle">40</td>
<td align="left" bgcolor="#dddddd" nowrap="nowrap" valign="middle"> C3H4
+ 4O2 = 3CO2 + 2H20</td>
</tr>
<tr>
<td align="center" bgcolor="#dddddd" valign="middle">Propadiene</td>
<td align="center" bgcolor="#dddddd" valign="middle">457</td>
<td align="center" bgcolor="#dddddd" valign="middle"> 
</td>
<td align="center" bgcolor="#dddddd" valign="middle">-34.5 
(-30)</td>
<td align="center" bgcolor="#dddddd" valign="middle">4</td>
<td align="center" bgcolor="#dddddd" valign="middle">114</td>
<td align="center" bgcolor="#dddddd" valign="middle">4.98</td>
<td align="center" bgcolor="#dddddd" valign="middle">5.24</td>
<td align="center" bgcolor="#dddddd" valign="middle">40</td>
<td align="left" bgcolor="#dddddd" nowrap="nowrap" valign="middle"> C3H4
+ 4O2 = 3CO2 + 2H20</td>
</tr>
<tr>
<td align="center" valign="middle">Diethyl Ether</td>
<td align="center" valign="middle">647</td>
<td align="center" valign="middle">1.85 - 36.5</td>
<td align="center" valign="middle">34.5 
(94)</td>
<td align="center" valign="middle">6</td>
<td align="center" valign="middle">108</td>
<td align="center" valign="middle">3.37</td>
<td align="center" valign="middle">3.49</td>
<td align="center" valign="middle">74</td>
<td align="left" nowrap="nowrap" valign="middle"> C4H10O
+ 6O2 = 4CO2 + 5H20</td>
</tr>
<tr>
<td align="center" valign="middle">Dimethyl Ether</td>
<td align="center" valign="middle">329</td>
<td align="center" valign="middle"> 
</td>
<td align="center" valign="middle">-25 
(-13)</td>
<td align="center" valign="middle">3</td>
<td align="center" valign="middle">110</td>
<td align="center" valign="middle">6.53</td>
<td align="center" valign="middle">6.98</td>
<td align="center" valign="middle">46</td>
<td align="center" valign="middle">C2H6O
+ 3O2 = 2CO2 + 3H20</td>
</tr>
</table>
'''Table Notes:'''
<ol>
<li>Additive and displasive volumes based on air containing 20.95%
(volume) oxygen.</li>
<li>MAPP gas is a proprietary mixture of various hydrocarbons,
principally methyl acetylene, propadiene and propane.</li>
<li>References: http://members.nuvox.net/F%7Eon.jwclymer/Frq/Fhoctable.html 
http://members.nuvox.net/F~on.jwclymer/Frq/Fhoctable.html 
http://home.fuse.net/clymer/rq combustion calculator 
http://www.nrc.gov/freading-rm/fdoc-collections/fnuregs/fstaff/fsr1805/ffinal-report/f15_explosion_calculations.xls
</li>
</ol>
<h2>"Traditional" Fuels</h2>
<h3>RightGuard</h3>
RightGuard, one of the traditional spudgun fuels, has undergone various
changes in composition over the years. Some types of RightGuard are
still usable as a spudgun fuel.
If the label has a warning about flammability and/or the ingredient
lists includes things like butane,
isobutane, or propane then it is
useable as a fuel. From the
Heats of Combustion table above you can see that there is relatively
little difference between these three ingredients. Even the optimum
volume percents are fairly close to each other. Since RightGuard is
generally used in the "squirt and screw" fueling mode, the actual
percent of fuel is difficult to
control. It seems likely that the other ingredients in the can make up
a fairly low percentage and probably have a relatively minor affect on
the energy of the fuel.
<h3>Aquanet</h3>
Aquanet, and similar hair sprays, have many of the same characteristics
as RightGuard. If the label warns that it is flammable, and if the
ingredient includes things like butane,
isobutane, or propane then it is
probably usable. As with RightGuard, the other ingredients in the can,
which may or may not be flammable, probably constitute a fairly low
percentage of the gas. There is the possibility that the other
ingredients may gum up the [[spark gap]], [[Chamber fan|fan]] or cleanout plug threads
after several uses.
<h3>Starter Fluid</h3>
By definition, automotive [[Starting fluid|starter fluid]] is combustible. There are no
doubt a couple of different formulations. One common formulation
includes 10~30% (weight) dimethyl ether and a propane propellant. Most
formulations should behave about the same as pure propane. 
<h3>Other Fuels</h3>
Pretty much any combustible compound that evaporates significantly
at ~70F can be used as fuel in a
combustion spudgun. Methanol, ethanol, isopropanol (rubbing alcohol),
gasoline, acetone (nail polish remover), paint thinner etc. can all be
used as fuel. The challenge with
these liquid fuels is getting them to evaporate in the gun in a
reproducible fashion. The actual energy
content of this type of fuel is
fairly irrelevant since the shot to shot reproducibility is so poor. It
really doesn't matter, with this type of fuel, whether the predicted
[[muzzle
velocity]] is 10% great with one fuel
versus another since the shot to shot variability is probably more like
50%. (Even with precisely metered propane,
the shot to shot variability in muzzle velocity for shooting [[potato|spuds]] is
typically in the 10 to 20% range.)
One thing that you should keep in mind with liquid fuels is the
potential for weakening the PVC. Take a look at the ingredients list on
your cans of PVC cleaner and [[PVC Glue|glue]]. Anything listed on those cans should
probably be avoided as fuels. Acetone and tetrahydrofuran (THF) in
particular are probably not the best idea for fuel since they soften
PVC.
<h2>Other Factors</h2>
The heat of combustion is not the only factor affecting the power of a
particular fuel. The rate at
which the fuel burns and the
maximum temperature and pressure obtained from the fuel also affects
the performance
of the gun.
<h3>Flame Speed and Power Law</h3>
Gaseous fuels burn at widely varying rates. For a combustion spudgun,
the faster the fuel burns the
better the gun will perform. Unfortunately, there is not a lot of
information available on the burn rates of various fuels. The table
below lists a few fuels of interests (values from
http://www.ub.uib.no/elpub/2004/h/404003/Hovedoppgave.pdf).
The flame front speed is how fast the flame moves through the mixture
at ambient conditions. In an actual combustion spudgun the flame front
accelerates as the temperature in the chamber rises. The flame front
speed as a function of temperature and pressure can be estimated using;
<blockquote>Flame speedi = (Flame speed0)*(Ti/T0)alpha*(Pi/P0)beta</blockquote>
Where Flame speed0, alpha and beta are the values shown in
the table below and Flame speedi is the speed at temperature
Ti and pressure Pi.
<table border="1" cellpadding="4" cellspacing="1">
<tr>
<td align="center" valign="middle"> Fuel</td>
<td align="center" valign="middle">Flame Front Speed,
meters/sec (FPS)</td>
<td align="center" valign="middle">Maximum Explosion Pressure
(ATM)</td>
<td align="center" valign="middle">Adiabatic Flame
Temperature, C (F)</td>
<td align="center" valign="middle">alpha</td>
<td align="center" valign="middle">beta</td>
</tr>
<tr>
<td align="center" valign="middle"> Methane</td>
<td align="center" valign="middle">0.45</td>
<td align="center" valign="middle">8.6</td>
<td align="center" valign="middle">2591 (4696)</td>
<td align="center" valign="middle">2.0</td>
<td align="center" valign="middle">-1.5</td>
</tr>
<tr>
<td align="center" valign="middle"> Propane</td>
<td align="center" valign="middle">0.43</td>
<td align="center" valign="middle">9.2</td>
<td align="center" valign="middle">2633 (4771)</td>
<td align="center" valign="middle">2.13</td>
<td align="center" valign="middle">-0.17</td>
</tr>
<tr>
<td align="center" valign="middle"> Hydrogen</td>
<td align="center" valign="middle">3.25</td>
<td align="center" valign="middle">7.9</td>
<td align="center" valign="middle">2755 (4991)</td>
<td align="center" valign="middle">1.26</td>
<td align="center" valign="middle">0.26</td>
</tr>
<tr>
<td align="center" valign="middle">Acetylene</td>
<td align="center" valign="middle">1.55</td>
<td align="center" valign="middle">9.6</td>
<td align="center" valign="middle">2918 (5284)</td>
<td align="center" valign="middle">2.0</td>
<td align="center" valign="middle">-0.06</td>
</tr>
</table>
As the table above shows, simple hydrocarbons such as methane and
propane, behave similarly, with
relatively slow flame front speeds and similar peak pressures and
temperatures. Hydrogen and
acetylene are substantially different. These two fuels burn much
faster, 3 to 8 times faster at standard conditions, than does propane.
 Hydrogen and acetylene have
another characteristic that differentiates them from fuels such as
propane of butane. Under certain conditions, hydrogen and acetylene
will
detonate (explode) instead of deflagrate (burn). When a fuel detonates
it releases all of
its energy essentially
instantaneously. The flame front speed in a detonation event is at
hyper-mach speeds (mach 6 to 7), roughly 4,000 times faster than the
laminar flame front speed (Mach ~0.001). Because of the very high burn
rate in a detonation, the gun is subjected to a tremendous shock force.
Most spudders believe that this level of stress is unsafe and that
hydrogen and acetylene are unsafe
fuels for a gun constructed from PVC.
<h2>Latke's Propane vs. MAPP
Study</h2>
Burnt Latke did a detailed study (
[http://www.burntlatke.com/lpmapprussets.html]) comparing the
muzzle velocities of propane and
MAPP</a>. Using a 1.5"D riffled barrel shooting spuds, Latke found that
MAPP out performed propane with
muzzle velocities of 444 (+/-34) FPS for MAPP and 398 (+/-34) FPS for
propane. So MAPP gave muzzle
velocities that were about 12% faster than propane. This increase in
performance is greater than what you would expect based solely on the
"Heat per mole Oxygen" values for the two fuels. If the muzzle velocity
scales as the square root of the ratio of the "Heat per mole Oxygen"
values, then MAPP would be expected to give muzzle velocities about ~4%
higher than propane. It is
possible that the 12% increase Latke observed is not statistically
different from the expected ~4% increase. Alternatively, MAPP may burn
slightly faster than propane.
Two of the components of MAPP, methyl acetylene and propadiene, would
be expected to have burn speeds that are more similar to acetylene than
propane.
<h2>So, What's the Best Fuel?</h2>
There really isn't a "best fuel"
for a combustion spud gun. If you want to get the maximum muzzle
velocity from a gun the difference between the various fuels is
relatively small. A typical combustion spud gun has so much shot to
shot variation in velocity that the relatively small difference between
fuels is not particularly relevant. Latke ([http://www.burntlatke.com/]), as good of a spudder as
there is, has done several studies using an accurate [[chronometer]] to
measure muzzle velocities. In all of his studies with spuds as
projectiles, using precisely metered fuels, the shot to shot
variability in muzzle velocity is typically in the 10 to 20% range. In
studies where Latke used the same round for several shots the
shot to shot variability is still in the 5% range. So it really doesn't
matter very much if one fuel has
5% more energy than another fuel.
 
 
The "best fuel" is the one that
the gunner is most comfortable with, that is easiest to obtain and use,
and is cheap. Beyond that there is really no significant difference
between fuels. 
 
There are other ways to get the best performance out of a combustion
spudgun. Here is my list, from most important to least important;
<ul>
<li>Mix the fuel well using a
chamber fan (like shown at [http://www.burntlatke.com/fan.html]).</li>
<li>Accurately measure the fuel
([http://home.earthlink.net/%7Ejimsluka/Sluka_Spud-zooka.html] describes a cheap
way, another at [http://home.earthlink.net/%7Ejimsluka/Fuel%20Meter%20From%20A%20Disposable%20Butane%20Lighter.html]
way, a way with much more "bling" is at [http://www.burntlatke.com/lp.html]).</li>
<li>Properly size the barrel to the chamber (or vice versa)</li>
<li>Increase the number of sparks</li>
</ul>
Any of these four will give much greater increases in performance than
will changing from, for example, propane
to MAPP. 
 
Originally posted at SpudTech.com on Fri
Feb 09, 2007
--[[User:Jimmy101|Jimmy101]] 13:53, 15 May 2007 (EDT)

Main Page

2008-06-04T06:18:54Z

Benstern: added links

== The Spudding Handbook ==
Welcome to The Spudding Handbook! This wiki format handbook contains all of the information you will ever need to build spudguns, and much more besides. The purpose of this handbook is to explain the principles of spudguns and how they are built and operated. All of the information contained in this handbook is free and available to anybody who wishes to view it.

Look around and enjoy your stay.
--[[User:BC Pneumatics|BC Pneumatics]] 02:13, 31 May 2008 (EDT)
[[Image:Cannon.jpg|frame|An Advanced Combustion Cannon]]
==What is a Spudgun?==
''Main article: [[What_is_a_spudgun%3F|What is a spudgun?]]''

There are many different names for spudguns. They are called potato cannons, spud launchers, potato guns, spud cannons, and a host of others. Whatever you decide to call it, all of the aforementioned describe the same type of device: a device used to accelerate a [[potato]] down the [[barrel]], and launch it some distance. While it may offend some purists, the humble little potato is quickly losing favor to other ammunitions such as [[golf ball]]s, [[tennis ball]]s, and other cheap, uniform projectiles.

==Types of Spudguns==

=== [[Pneumatic_launcher|Pneumatic Launchers]] ===

These use the energy stored in compressed gas to launch a projectile. The launcher's [[chamber]] is [[pressure|pressurized]] and the gas held back from the barrel by a [[valve]]. When the valve is opened the gas is allowed to rapidly expand and escape down the barrel forcing the projectile out before it.

=== Combustion Launchers ===

* '''[[Combustion_launcher|Regular Combustions]]'''

These find the energy needed to launch a projectile from the [[Combustion process|combustion]] of a gaseous [[fuel]] and air mixture. The fuel is added to the air already in the chamber, the chamber is sealed and the mixture ignited. This combustion creates a pressure spike that forces the projectile out through the connected barrel.

* '''[[Hybrid_launcher|Hybrid Launchers]]'''

Hybrid launchers are a special type of combustion launcher that use a pre-pressurised fuel/air mixture. This results in a higher pressure and hotter combustion on ignition, thereby transferring more energy to the projectile.

=== [[BB Machine Gun]]s ===
A [[BB Machine Gun]] (BBMG) is a device designed to shoot a large volume of small diameter ammo, typically plastic airsoft or steel BBs. BBMGs are pneumatic guns but unlike single shot launchers they require a constant gas supply to function.

==Important & Related Links==

[[Index|Glossary/Index]]

[[BCARMS]]

[[Useful construction links]]

[[Launcher configuration]]

[[Computer Applications]]

[[IPLA|International Potato Launching Association]]

[[Safety]]

[[Ammunition]]

[[Legal issues]]

[[History]] (A Brief History of Spud Guns)

[[SpudFiles forum guidelines]]

==External links==

*[http://en.wikipedia.org/wiki/Spud_gun Wikipedia's page on spudguns]
*[http://www.bavetta.com/aircannon.html Air Cannon Barrel Length Numerical Analysis]
*[http://www.thehalls-in-bfe.com/GGDT Gas Gun Design Tool, simulation program for pneumatic guns]
*[http://www.spudfiles.com/forums/viewtopic.php?p=13324#13324 ATF Correspondence concerning spud gun legality]
*[http://www.spudfiles.com SpudFiles Forum (aka The Spud Cannon Database)]
*[http://www.BCARMS.com BCARMS - Spud Cannon Parts, Accessories, Kits and Launchers]

BB machine gun

2008-06-04T06:04:22Z

Benstern: added link

A '''BB Machine Gun''' (BBMG) is a device designed to shoot a large volume of small diameter [[ammo]], typically plastic airsoft or steel BBs. BBMGs are pneumatic guns but unlike single shot [[pneumatic launcher|launchers]] they require a constant gas supply to function. The common use of a large air [[compressor]] restricts mobility for the majority of BBMGs although models using CO2 systems have been successfully built as portable units.

== Common Designs ==

* A [[Cloud BBMG]] agitates the BBs in the ammunition chamber by means of the air inlet blowing upwards through them. The agitated BBs then get sucked into the [[barrel]] with the outgoing air stream.

* A [[Tee vortex BBMG]] housed inside of the bottom of a [[tee]], uses the air inlet to swirl the BBs around a circular or semi-circular cutout in a block placed in the BB [[chamber]] and out through a BB sized hole in its side leading to the barrel.

* An [[Inline Vortex BBMG]] uses the same [[vortex block]] from above however the block is housed inside a straight pipe. Normally Inline Vortex BBMG's have a spring/plunger system that forces the BB's into the vortex block to allow firing from any angle without agitation.

* A [[Vortex cap BBMG]] works on an identical principle to a vortex block but instead of a cut-out in a block placed within a large BB chamber it uses the circular internals of a pipe endcap in which to swirl the BBs allowing for a smaller diameter chamber. This potentially allows for a smaller overall design. It was designed by Gatorlangman AKA DavidVaini.

== Design Characteristics ==

The performance of a BBMG, as with any gun, depends on specific characteristics. For BBMGs, perhaps the most important are;

* Air supply [[pressure]]
* Sustainability of the supply pressure
* Air flow from supply to barrel
* Barrel length
* The fit of the BBs in the barrel

Most of the characteristics that make a good pneumatic spudgun also apply to BBMGs. As with any pneumatic gun, the higher the reservoir pressure and the longer the barrel (up to a point) the greater the [[muzzle velocity]]. Because of the large amount of compressed gas that is wasted in a typical BBMG, the air supply needs to be fairly substantial. For air supplies with a resevoir such as compressors this can mean [[CB ratio]]s of 100:1 to 1000:1. Note that, for a BBMG, the "chamber volume" includes the volume of the compressor's reservoir.

The BBs should fit the barrel well enough to minimize leakage of air around the ammo ([[blowby]]) but not so tightly that friction is excessive.

The chambering and firing of BBs in a cloud BBMG appears to be a coupled process. Usually, when a BB is passing through the barrel the reduced air flow through the gun inhibits the loading of the next BB into the barrel. When the first BB leaves the barrel the increase in air flow "chambers" the next BB. As a result it appears that there is rarely more than one BB in the barrel at a time. This suggests that the muzzle velocity and ROF of cloud BBMGs are linked. The ROF for a gun would appear to be often very close to the reciprocal of the barrel transit time for a BB.

For example, a 3 foot barrel that fires at 300 FPS has an average barrel velocity of ~150 FPS and a transit time of ~20mS. The ROF would be expected to be about 1/20mS = 50 RPS. Design changes that alter the transit time would be expected to also change the ROF. When adding the feeding system of a vortex block this becomes less of a problem because vortex blocks are more of a forced air system rather than a suction system such as cloud BBMGs.

== Typical Performance ==

The rate of fire for the average gun is very high, in the vicinity of 30 to 100 rounds per second (RPS), 1800 to 6000 rounds per minute, comparable to that of a [http://en.wikipedia.org/wiki/Minigun Minigun] which clocks in at 33~66 RPS.

BBMGs in general are not usually capable of sustained full performance fire as most air sources cannot provide an adequate flow of sufficiently high pressure air. To reduce air consumption, maintain muzzle velocity and to reduce the rate that the ammunition is expended they are typically fired in short bursts lasting a few seconds at most.

'''Airsoft BBMG Performance'''

Airsoft BBMGs are known for their especially high rate of fire. This is in the region of 30 to 115 rounds per second (RPS), 1800 to 6900 rounds per minute. This is useful in Airsoft skirmishes for laying down suppressive fire or clearing out multiple targets up close. The projectile speeds of around 250-400 Feet Per Second(FPS) are comparable to higher end Airsoft Electric Guns or AEGs. The advantage of the high ROF is quite clear in skirmishes however the consumption of such a high volume of pellets can be expensive.

Other disadvantages of using BBMGs in airsoft lies in their portability and range. Portability can be fixed by using an external CO2 setup for the gas supply however it can be costly. The other problem of range is due to the lack of a hop-up system which creates backspin on the BB and so increase the distance they can fly. Although possible to add a hop-up they wear down quickly because of the high ROF.

'''Non-Airsoft BBMG Performance'''

These BBMGs are unregulated by airsoft limitations of plastic pellets as they are not intended to be fired at other people.

With 3 foot length of 1/4" OD (3/16" ID) stainless steel tubing, a 120 PSIG 3 gallon shop compressor and firing standard copper or steel BBs, a typical vortex BBMG has a muzzle velocity of about [http://www.inpharmix.com/jps/Jims_chrono.html 330 FPS]. This is about the same as a cheap commercial single shot BB gun. The muzzle energy for an 0.177" metal BB (0.33g) at 330 FPS is 1.2 foot-pounds (1.7J). Despite the relatively low projectile speed, the abrasive effects of a large number of hard BBs striking a target in a short period of time can be quite destructive.

The high ROF can consume pellets at an expensive rate. A six pound container of 6000 metal BBs costs about $15. At 50 RPS that six pound container will last for two minutes of firing.

== Links ==
[http://www.burntlatke.com/bb.html Latke's BBMG]: An excellent write-up on how to build a Vortex BBMG.

[[Category:BB machine gun]]

Inline Vortex BBMG

2008-06-04T06:02:09Z

Benstern: fixed link

An Inline Vortex BBMG as the name suggests, is a [[BB machine gun|BBMG]] that uses a [[vortex block]] as the main feeding system. The inside of the vortex block is where all the magic happens. The inside is circular in shape and guides the BBs around and around until they get chambered into the [[barrel]]. What causes the BBs to spin around is the stream of air supplied from the air inlet. None of this would matter though if the BB's could not make it to the vortex block. With the traditional [[Tee vortex BBMG|tee vortex block BBMG]] you would have to aim down for the gun to fire or shake the gun up and down. This can be solved by adding a [[plunger system]] that pushes the BBs towards the vortex block at all times and directions. Shown below is an animation that shows this concept.

[[Image:Inlinevortexanimationgiffinal2.gif]]

= Examples of Inline Vortex BBMGs =

<gallery widths="175px" heights="175px" perrow="3">
Image:IVexample1.jpg
Image:IVexample2.jpg
Image:IVexample3.jpg
Image:IVexample4.jpg
Image:IVexample5.jpg
Image:IVexample6.jpg
Image:IVexample7.jpg
Image:IVexample8.jpg
</gallery>

[[Category:BB machine gun]]

Vortex block

2008-06-04T06:00:29Z

Benstern: added and fixed links

This specifically shaped object made of a semi-hard to hard material is used in both [[Tee vortex BBMG|tee vortex]] and [[Inline Vortex BBMG|inline vortex BBMG]]s. It is located inside the [[chamber]] of the gun and is designed to take BB's located outside of this part and suck them into the [[barrel]] of the [[BB machine gun]] using what is known as the Venturi effect.

Some people use lathes in order to turn pieces metal (usually aluminum) or plastic for the construction of a vortex block, while others prefer using either [http://www.bondo-online.com/catalog_item.asp?itemNbr=176 Bondo Auto Body Filler] or epoxy molded in a PVC plug. Designs for building a Bondo vortex can be found on Burnt Latke's [http://www.burntlatke.com/bb.html BB machine gun construction] page.

= Examples of vortex blocks =

<gallery widths="175px" heights="175px" perrow="3">
Image:TVexample7.jpg|A metal vortex block for use in a tee
Image:TVexample8.jpg|A vortex block constructed from Bondo for use in a tee
</gallery>

[[Category:BB machine gun]]

Vortex block

2008-06-04T05:57:12Z

Benstern: made page about vortex blocks, added gallery, added bb machine gun category

This specifically shaped object made of a semi-hard to hard material is used in both [[Tee vortex BBMG|tee vortex BB machine guns]] and [[inline vortex BBMG]]s. It is located inside the [[chamber]] of the gun and is designed to take BB's located outside of this part and suck them into the [[barrel]] of the BBMG using what is known as the Venturi effect.

Some people use lathes in order to turn pieces metal (usually aluminum) or plastic for the construction of a vortex block, while others prefer using either [http://www.bondo-online.com/catalog_item.asp?itemNbr=176 Bondo Auto Body Filler] or epoxy molded in a PVC plug. Designs for building a Bondo vortex can be found on Burnt Latke's [http://www.burntlatke.com/bb.html BB machine gun construction] page.

= Examples of vortex blocks =

<gallery widths="175px" heights="175px" perrow="3">
Image:TVexample7.jpg|A metal vortex block for use in a tee
Image:TVexample8.jpg|A vortex block constructed from Bondo for use in a tee
</gallery>

[[Category:BB machine gun]]

Tee vortex BBMG

2008-06-04T05:56:59Z

Benstern: changed to focus on the bbmg and not vortex blocks, added gallery, added to bb machine gun and stubs categories

This is the oldest type of the vortex variety of [[BB machine gun]]s. It is made by installing a [[vortex block]] inside a [[tee]] fitting. They help comprise a portion of the [[chamber]], which holds the BBs. This design necessitates that the [[barrel]] be positioned below the chamber of the BBMG.

[[Image:Vortexanimated.gif]]

= Examples of Tee Vortex BBMGs =

<gallery widths="200px" heights="200px" perrow="3">
Image:TVexample1.jpg
Image:TVexample2.jpg
Image:TVexample3.jpg
Image:TVexample4.jpg
Image:TVexample5.jpg
Image:TVexample6.jpg
</gallery>

[[Category:BB machine gun]]
[[Category:Stubs]]

BB machine gun

2008-06-04T05:12:26Z

Benstern: added and fixed links, added to bb machine gun category

A '''BB Machine Gun''' (BBMG) is a device designed to shoot a large volume of small diameter [[ammo]], typically plastic airsoft or steel BBs. BBMGs are pneumatic guns but unlike single shot [[pneumatic launcher|launchers]] they require a constant gas supply to function. The common use of a large air [[compressor]] restricts mobility for the majority of BBMGs although models using CO2 systems have been successfully built as portable units.

== Common Designs ==

* A [[Cloud BBMG]] agitates the BBs in the ammunition chamber by means of the air inlet blowing upwards through them. The agitated BBs then get sucked into the [[barrel]] with the outgoing air stream.

* A [[Tee vortex BBMG]] housed inside of the bottom of a [[tee]], uses the air inlet to swirl the BBs around a circular or semi-circular cutout in a block placed in the BB [[chamber]] and out through a BB sized hole in its side leading to the barrel.

* An [[Inline Vortex BBMG]] uses the same vortex block from above however the block is housed inside a straight pipe. Normally Inline Vortex BBMG's have a spring/plunger system that forces the BB's into the vortex block to allow firing from any angle without agitation.

* A [[Vortex cap BBMG]] works on an identical principle to a vortex block but instead of a cut-out in a block placed within a large BB chamber it uses the circular internals of a pipe endcap in which to swirl the BBs allowing for a smaller diameter chamber. This potentially allows for a smaller overall design. It was designed by Gatorlangman AKA DavidVaini.

== Design Characteristics ==

The performance of a BBMG, as with any gun, depends on specific characteristics. For BBMGs, perhaps the most important are;

* Air supply [[pressure]]
* Sustainability of the supply pressure
* Air flow from supply to barrel
* Barrel length
* The fit of the BBs in the barrel

Most of the characteristics that make a good pneumatic spudgun also apply to BBMGs. As with any pneumatic gun, the higher the reservoir pressure and the longer the barrel (up to a point) the greater the [[muzzle velocity]]. Because of the large amount of compressed gas that is wasted in a typical BBMG, the air supply needs to be fairly substantial. For air supplies with a resevoir such as compressors this can mean [[CB ratio]]s of 100:1 to 1000:1. Note that, for a BBMG, the "chamber volume" includes the volume of the compressor's reservoir.

The BBs should fit the barrel well enough to minimize leakage of air around the ammo ([[blowby]]) but not so tightly that friction is excessive.

The chambering and firing of BBs in a cloud BBMG appears to be a coupled process. Usually, when a BB is passing through the barrel the reduced air flow through the gun inhibits the loading of the next BB into the barrel. When the first BB leaves the barrel the increase in air flow "chambers" the next BB. As a result it appears that there is rarely more than one BB in the barrel at a time. This suggests that the muzzle velocity and ROF of cloud BBMGs are linked. The ROF for a gun would appear to be often very close to the reciprocal of the barrel transit time for a BB.

For example, a 3 foot barrel that fires at 300 FPS has an average barrel velocity of ~150 FPS and a transit time of ~20mS. The ROF would be expected to be about 1/20mS = 50 RPS. Design changes that alter the transit time would be expected to also change the ROF. When adding the feeding system of a vortex block this becomes less of a problem because vortex blocks are more of a forced air system rather than a suction system such as cloud BBMGs.

== Typical Performance ==

The rate of fire for the average gun is very high, in the vicinity of 30 to 100 rounds per second (RPS), 1800 to 6000 rounds per minute, comparable to that of a [http://en.wikipedia.org/wiki/Minigun Minigun] which clocks in at 33~66 RPS.

BBMGs in general are not usually capable of sustained full performance fire as most air sources cannot provide an adequate flow of sufficiently high pressure air. To reduce air consumption, maintain muzzle velocity and to reduce the rate that the ammunition is expended they are typically fired in short bursts lasting a few seconds at most.

'''Airsoft BBMG Performance'''

Airsoft BBMGs are known for their especially high rate of fire. This is in the region of 30 to 115 rounds per second (RPS), 1800 to 6900 rounds per minute. This is useful in Airsoft skirmishes for laying down suppressive fire or clearing out multiple targets up close. The projectile speeds of around 250-400 Feet Per Second(FPS) are comparable to higher end Airsoft Electric Guns or AEGs. The advantage of the high ROF is quite clear in skirmishes however the consumption of such a high volume of pellets can be expensive.

Other disadvantages of using BBMGs in airsoft lies in their portability and range. Portability can be fixed by using an external CO2 setup for the gas supply however it can be costly. The other problem of range is due to the lack of a hop-up system which creates backspin on the BB and so increase the distance they can fly. Although possible to add a hop-up they wear down quickly because of the high ROF.

'''Non-Airsoft BBMG Performance'''

These BBMGs are unregulated by airsoft limitations of plastic pellets as they are not intended to be fired at other people.

With 3 foot length of 1/4" OD (3/16" ID) stainless steel tubing, a 120 PSIG 3 gallon shop compressor and firing standard copper or steel BBs, a typical vortex BBMG has a muzzle velocity of about [http://www.inpharmix.com/jps/Jims_chrono.html 330 FPS]. This is about the same as a cheap commercial single shot BB gun. The muzzle energy for an 0.177" metal BB (0.33g) at 330 FPS is 1.2 foot-pounds (1.7J). Despite the relatively low projectile speed, the abrasive effects of a large number of hard BBs striking a target in a short period of time can be quite destructive.

The high ROF can consume pellets at an expensive rate. A six pound container of 6000 metal BBs costs about $15. At 50 RPS that six pound container will last for two minutes of firing.

== Links ==
[http://www.burntlatke.com/bb.html Latke's BBMG]: An excellent write-up on how to build a Vortex BBMG.

[[Category:BB machine gun]]

"T" vortex BBMG

2008-06-04T05:07:06Z

Benstern: "T" vortex BBMG moved to Tee vortex BBMG: Proper use of a fitting name rather then a shortened version

#REDIRECT [[Tee vortex BBMG]]

Tee vortex BBMG

2008-06-04T05:07:06Z

Benstern: "T" vortex BBMG moved to Tee vortex BBMG: Proper use of a fitting name rather then a shortened version

This specifically shaped object made of a semi-hard to hard material is used in a [[BB machine gun]] to take bb's located outside of this part and suck them into the [[barrel]] of the [[BB machine gun]]. Some people use lathes in order to turn pieces of aluminum for the construction of a vortex, while others prefer using [http://www.bondo-online.com/catalog_item.asp?itemNbr=176 Bondo Auto Body Filler] molded in a PVC plug. Designs for building a Bondo vortex can be found on Burnt Latke's [http://www.burntlatke.com/bb.html BB machine gun construction] page.

[[Image:Vortexanimated.gif]]

[[Tee Vortex BBMG Gallery]]

Strafer

2008-06-04T05:03:52Z

Benstern: changed from manual redirection to automatic

#REDIRECT [[BB machine gun]]

BBMG

2008-06-04T05:00:02Z

Benstern: changed from manual redirection to automatic

#REDIRECT [[BB machine gun]]

Vortex cap BBMG

2008-06-04T04:56:11Z

Benstern: added links, resized and thumbnailed image, added gallery, added to BB machine gun category

This type of [[BB machine gun]] has a unique mechanism of operation and is typically a cap in shape and is made out of strong materials such as PVC or metal. Their construction is similar to the [[vortex block]], in which an air inlet and a hole for a [[barrel]] are drilled perpendicular to each other. The vortex cap was designed by Gatorlangman and provides a small substitute to the standard vortex or [[Inline Vortex BBMG|inline vortex]] blocks.

Since the cap itself creates the vortex easy modifications can be done to make magazines. A screw on cap with a spring housed inside of a pipe can be snapped down into a vortex cap for an easy-to-use magazine loaded system. Some of the designs for magazines are shown in the image below:

[[Image:vortexcapimage1.jpg|thumbnail|center|700px]]

= Examples of Vortex cap BBMGs =

<gallery widths="200px" heights="200px" perrow="3">
Image:VCexample1.jpg
Image:VCexample2.jpg
Image:VCexample3.jpg
</gallery>

[[Category:BB machine gun]]

Talk:Inline Vortex BBMG

2008-06-04T04:33:28Z

Benstern: New page: The animated picture on this article has to either be fixed or removed. For it to be considered "fixed" the following needs to happen: *The black bars on the top and bottom need to be re...

The animated picture on this article has to either be fixed or removed.

For it to be considered "fixed" the following needs to happen:

*The black bars on the top and bottom need to be removed
*The watermark needs to be removed.
*The labeling of the air intake, barrel, and threaded cap need to be of a size large enough to be easily read.
*Image needs have it's dimensions resized so it only fits the contents and has little to no extraneous space

If the source file (the original file before conversion) is sent to me I can make these changes myself. (I can handle FLA, SWF, GIF, and whatever file formats the original image used)

Thanks,
Benstern

Inline Vortex BBMG

2008-06-04T04:23:14Z

Benstern: made the section tite more noticable

An Inline Vortex BBMG as the name suggests, is a [[BB machine gun|BBMG]] that uses a [[vortex block]] as the main feeding system. The inside of the vortex block is where all the magic happens. The inside is circular in shape and guides the BBs around and around until they get chambered into the [[barrel]]. What causes the BBs to spin around is the stream of air supplied from the air inlet. None of this would matter though if the BB's could not make it to the vortex block. With the traditional [["T" vortex BBMG|"T" Vortex block BBMG]] you would have to aim down for the gun to fire or shake the gun up and down. This can be solved by adding a [[plunger system]] that pushes the BBs towards the vortex block at all times and directions. Shown below is an animation that shows this concept.

[[Image:Inlinevortexanimationgiffinal2.gif]]

= Examples of Inline Vortex BBMGs =

<gallery widths="175px" heights="175px" perrow="3">
Image:IVexample1.jpg
Image:IVexample2.jpg
Image:IVexample3.jpg
Image:IVexample4.jpg
Image:IVexample5.jpg
Image:IVexample6.jpg
Image:IVexample7.jpg
Image:IVexample8.jpg
</gallery>

[[Category:BB machine gun]]

Inline Vortex BBMG

2008-06-04T04:16:51Z

Benstern: added links, fixed grammar, added gallery, created and added bb machine gun category

An Inline Vortex BBMG as the name suggests, is a [[BB machine gun|BBMG]] that uses a [[vortex block]] as the main feeding system. The inside of the vortex block is where all the magic happens. The inside is circular in shape and guides the BBs around and around until they get chambered into the [[barrel]]. What causes the BBs to spin around is the stream of air supplied from the air inlet. None of this would matter though if the BB's could not make it to the vortex block. With the traditional [["T" vortex BBMG|"T" Vortex block BBMG]] you would have to aim down for the gun to fire or shake the gun up and down. This can be solved by adding a [[plunger system]] that pushes the BBs towards the vortex block at all times and directions. Shown below is an animation that shows this concept.

[[Image:Inlinevortexanimationgiffinal2.gif]]

== Gallery ==

<gallery widths="175px" heights="175px" perrow="3">
Image:IVexample1.jpg
Image:IVexample2.jpg
Image:IVexample3.jpg
Image:IVexample4.jpg
Image:IVexample5.jpg
Image:IVexample6.jpg
Image:IVexample7.jpg
Image:IVexample8.jpg
</gallery>

[[Category:BB machine gun]]

Talk:Chamber fan

2008-06-04T03:43:36Z

Benstern: New page: I have a few questions. 1) By "'''quick vent plug'''", do you mean Quick disconnect? 2) I am pretty sure that I have have heard of pc case fans melting in combustion spudguns. Can so...

I have a few questions.

1) By "'''quick vent plug'''", do you mean [[Quick disconnect]]?

2) I am pretty sure that I have have heard of pc case fans melting in combustion spudguns. Can someone verify this?

3) I believe that good amount of high heat in the combustion chamber lasts longer then "a few milliseconds" after combustion has ended.

4)Can someone confirm or deny the statement about turbulence of the flame front being undesirable in hybrids due to increased risk of DDT?

Thanks,
benstern

Chamber fan

2008-06-04T03:32:05Z

Benstern: added links, fixed spelling and grammar. added to accessories category

[[image:Chamberfan.JPG|right|thumb|300px|A 92mm chamber fan at the back of a cannon.]]
A '''chamber fan''' is an improvement mostly used in [[combustion cannon]]s, though [[hybrid cannon]]s sometimes also have one. The fan will improve [[muzzle velocity]], power and usability. It is a recommended upgrade and may improve the power of your cannon with 20-50%. Sometimes more then one fan is used.
For exact information on performance gains see [http://www.burntlatke.com/jpg600/fan-data.gif this latke test].

==Purposes==
They have multiple purposes:

*Mixing
*[[Venting]]
*Inducing turbulence

Their main purpose of increasing cannon performance is '''mixing''' the air or [[oxygen]] with the [[fuel]]. This creates an even mix and significantly increases performance. Unmixed chambers may have way too much fuel on one side of the [[chamber]], while a lack of fuel exists on the other side. The chamber fan fixes this and helps having a good [[stoichiometry]] throughout the chamber.

Another purpose is '''venting'''. After each shot the burnt fuel mixture needs to get out of the cannon and fresh air needs to be put in. This is because (almost) all oxygen is used during the [[Combustion process|combustion]] and new oxygen is needed for a new combustion. When the back end of the chamber is opened up using either a cap or some other system like a [[ball valve]] or quick vent plug, the fan effectively blows out all air and sucks in fresh air. With a chamber fan venting is done much faster and much more reliable.

The last purpose counts if the fan is on during combustion: '''turbulence''' is induced because the air inside the chamber is moving. This causes the flame front to speed up, and thus the combustion goes faster. This further increases the performance of the cannon.
Theories exist tell that two smaller fans blowing in opposite directions induce more turbulence though they wont do very well on venting.

==Types of fans==

The most commonly used fans are case fans out of computers. The corners may be sanded down so it fits in the chamber, and sometimes the complete frame around the fan is cut off and even the fan blades need to be cut for fitting it into in small chambers.
Instead of PC fans you could also use any other electric motor with fan blades attached. However, you should avoid brushed motors at all times. PC fans have brushless motors and thus do not create any sparks within. A brushed motor could spark with the possibility of suddenly igniting the fuel mixture, which can lead to [[safety|accidents]] damaging the environment or even harming people. So now and then someone still uses a brushed engine but sealed the holes in the housing off with glue, making sure no fuel can enter the insides of the engine. The engine wont be able to cool itself anymore, but when used in short periods, that doesn't really matter.

Since PC fans are cheap, brushless and readily available in various sizes, this is the choice of most spudders and the most recommended option.
Further characteristics of fans are noise, CFM (the amount of air it displaces) and RPM (how fast it rotates). Noise doesn't really matter for a cannon, and you probably want to have an high CFM, high RPM fan for some good mixing.

== Powering, wiring and mounting the fan ==

'''Powering the fan'''

Nearly all fans are powered by a pack of batteries. A 12V fan can be ran off a single 9V battery (though it will not run at full power) or a bunch of 8 1.5V batteries. It is also useful to have a switch to turn the fan on and off. It can also be controlled automatically using a [http://www.burntlatke.com/fan-controller.html timer circuit] which turns the fan off when it's not needed. For a good looking cannon without duct tape and wires all over it, you build all the fan circuitry and batteries into a fan control box. Since the same can be done with ignition systems in a ignition control box, some people merge it together into one fan/ignition control box. This gives the advantage of running a fan and a [[stungun]] from the same batteries, saving space and weight. Sometimes this box is built in the handle for an even cleaner look not showing any wires.

'''Mounting & wiring the fan'''

The easiest way of doing this is having a PC fan which is a bit too large. Sand down the corners until it fits in tight and squeeze it in. The fan will stay in place due to friction. Glue can be used to secure the fans and sometimes bolts are used too.

Since the batteries and possibly switch are outside the chamber while the fan is inside, you will need to get those two wires to the fan someway.
A leak free way of doing so is screwing in two bolts trough the chamber wall (preferably drill through both the pipe and fitting so you've got two layers of PVC/ABS.) Then attach the wires on the inside and the outside to the bolts and your done.

'''Fan placement'''

It is not recommended to place the fan too much near the [[barrel]] opening. Remember that all air behind the fan wants to go past it and if that is too much you will constrict flow to the barrel and most importantly: your fan will probably break. Most fans are at the back of the chamber so they can easily be taken out for service on the chamber or the fan. Note that you cant take a fan out when the electrode bolts are in the way.

==Will my fan survive the combustion?==

If you think that your fan might get burned or melt, don't worry, it wont. Since the heat in the combustion chamber lasts no more then a few milliseconds the fan doesn't have time to heat up or melt. As stated above, your fan should not be too close to the barrel. If its more to the back, it wont get blown to pieces due to the extreme flow.

A fan may have a somewhat shortened lifespan inside a combustion chamber, but it still can survive for many years. So for combustion cannons: Yes, your fan will survive.

In hybrids fans last shorter due to the more extreme environment. High-mix hybrids can break their fans on the first shot. Luckily, those hybrids don't need fans anyway. When you pressurize the fuel mixture with air after you have put in the fuel, the blow-in of air already mixes the fuel. Also because of [[DDT]] dangers you don't want to have turbulence anyway.

[[Category:Accessories]]