SpudFiles Wiki - User contributions [en]

Quick Dump Valve

2009-08-27T23:10:38Z

Boilingleadbath: + cross section

'''Article Flag''' 
As an article relating to spudding hardware, this should be presented in a more neutral format - it currently reads like an advertisement. 
It should also be presented in a third person point of view, as newcomers won't be able to associate "I" or "Me" usefully. 
Flagged by [[User:Ragnarok|Ragnarok]] 20:32, 29 July 2009 (EDT)

== The Quick Dump Valve ==
[[Image:Wtooliepiston.png|frame|Toolie-style piston valve; A is barrel, B is sealing face, C is chamber, D is drive rod, E is piston, F is pilot volume, G is pilot valve.]]
The quick dump valve is a variation on a traditional barrel sealer piston valve. In the section on piston valves, various configurations are covered and the advantages and disadvantages of each. A quick dump valve may be used where the traditional valves shortcomings cause problems for the builder. It was noted in the piston valve section in the wiki that as a barrel sealer valve nears a 1:1 ratio, the pilot pressure needed to open the valve drops lower, and when they pop open, they do so with more force and speed. They become temperamental as the ratio approaches a 1:1 ratio as the force to start opening the valve drops. They tend to stick or are unable to vent the pilot low enough to fire it. As a result, piston valves that won't fire are a common problem.

The Quick Dump Valve or QDV was built to take advantage of close ratio piston valve advantages of speed while fixing the disadvantages of the temperamental nature of them failing to fire reliably or seal properly to build chamber pressure.

Spool valves are balanced design valves with several o rings that move past ports and are operated by the rings crossing ports to join some in the same segment or separate them. They are noted for the ability to switch high pressures with little force to operate the valve. Typical uses are the hydraulic controls on heavy machinery such as a backhoe. Normal spool valves have both ends of the valve rod at atmospheric pressure.

A QDV when closed has the appearance of a spool valve. The air source under pressure is sealed off in the chamber with an o ring on both sides of the port. What makes this different than a typical spool valve is when it is opened, the supply pressure is then applied to the end of the spool. This pressure provides a positive feedback to the spool so as it opens, the force opening it rapidly increases as supply pressure in the outlet port pushes on the piston.

Unlike a piston valve that uses pressure in a "Pilot" area to hold the valve closed, the QDV has no pressure on the pilot area of the piston to hold it closed. In this manner it is much like a spool control valve.

A video on the valve theory is posted here; [http://www.youtube.com/watch?v=No3nI07mlQo Youtube The Quick Dump Valve]

The first appearance of the Quick Dump Valve in an air cannon is covered in a contest for building t shirt launchers;
[http://inteltrailblazerschallenge.wikispaces.com/The+brag+zone IntelTrailBlazers Engineering Challenge]

The first mention of the valve on Spudfiles is in this thread.
[http://www.spudfiles.com/forums/interesting-new-valve-design-t17617.html Interesting New Valve Design]

This is a video of the T Shirt launcher in action. The team won the competition with this design.
[http://www.youtube.com/watch?v=9Klxqav_6NM Quick Reload T Shirt launcher]

Quick Dump valves can be constructed as either a coaxial design with the valve inside a chamber, or built inside a T for an external valve. Coaxial valves provide some of the best COF values possible.

[[Image:WikiOverview.jpg]]

The oldest is constructed with ABS. The valve is located in the breech of the chamber. The barrel is a long pipe that extended all the way though the chamber with ports cut into the pipe between the chamber and barrel. A plastic bag was stuffed into the barrel to highlight the ports for the photo. Otherwise they were too dark to see very well.

[[Image:ValvePorts1.JPG]]

This design works well. The drawbacks are the piston needs a rod shoved into the breech rope pull hole to reset the valve between shots and the design did not use floating o rings, so it pulls a little hard.

The piston is made from a piece of PVC pipe and a couple pipe caps and o rings. Any sturdy cylindrical object can be used that will hold the pressure and forces.

[[Image:CoreDetail.JPG]]

For safety on this design, it is very important to remember that shoving anything into the barrel does the same thing as pulling the rope. It opens the valve. ''' Never shove anything into this design of valve while it is under pressure.''' Load it and then add pressure.

The spudfiles page on the cannon is here;
[http://www.spudfiles.com/forums/abs-cellular-core-test-cannon-t17968.html ABS Cellular Core Test Cannon, also known as the apple cannon]
It was posted as a materials test discussion on using unrated plastic pipe in air cannons.

Later improvements to the design included using a rod instead of a rope to open and close the valve. The piston if permitted to slide freely on the rod can be made to operate quickly without having to accelerate the control trigger rod. In operation, when the rod is pushed in, a pin on the rod pushes the piston closed. To fire the rod is pulled back through the piston which retracts the pin behind the piston out of the piston travel area. Then a nut on the end of the rod pushes the front of the piston pulling it open triggering it. Once the valve cracks open, the air pressure between the piston and projectile pushes the valve open with the same pressure it applies to the projectile.

The valve can be relocated to the barrel end of the chamber.
This permits easy detachment of the barrel and the ability to attach various size barrels with minimum dead space.

A model of the T Shirt launcher shows the construction detail with the improvements. In Spudfiles, it is called the Marshmallow Cannon. It was built for a high speed marshmallow launching competition. With a removable and interchangeable barrel selection, it is easy to adapt to shooting gumballs, jawbreakers, batteries, tennis balls, and t shirts. With a 36 inch long t shirt barrel the 1 inch valve is able to toss shirts 200 feet.

The Spudfiles entry is here;
[http://www.spudfiles.com/forums/quick-dump-valve-t17858.html The Quick Dump Valve]
The spudfiles entry has links to a theory of operation video as well as more photos.

The tank as before is coaxial design with a valve body in the center. Unlike the earlier design, the barrel is removable and the valve is located at the barrel end of the chamber instead of the breech. The new design uses a rod to trigger and reset the valve.

[[Image:WikiTank.jpg]]

The valve core removed from the tank shows the piston with floating rings, rod, bumper, stopper, and trigger and reset pins.

[[Image:WikiVavleCoreAssy.jpg]]

A close up view of the piston shows the o rings fit loose in a floating O Ring design. The spudfiles page and linked videos show how this style of o ring installation lowers the friction in the valve.

[[Image:Piston_rings.jpg]]

The ports between the chamber and valve body can be seen inside the valve.

[[Image:WikiTankEnd.jpg]]

View of the assembled cannon with the tennis ball barrel. It tosses tennis balls 100 yards.

[[Image:Tennis_ball_barrel1.jpg]]

With high speed of operation and a high flow, the cannon is able to deliver high speeds. The photo is a 2X4 that was split with a couple jawbreakers.

[[Image:Split1a.JPG]]

Photos are copyright by Technician1002. Please ask before using elsewhere.

Triggered burst disk

2009-08-27T23:05:25Z

Boilingleadbath: formatting fail

[[Image:Triggered_burstdisk.PNG|frame|The firing cycle of a triggered burst disk]][[Image:Triggeredburstdisk2.png|frame|An example of a mechanically triggered burst disk; for the purpose of the example, D is a broad head.]]
A triggered [[burst disk]] system allows the user to accurately control the time of firing, in one of two ways:

== Cascade Failure ==
Cascade failure systems consist of two burst disks mounted between the [[chamber]] and [[barrel]] of a [[pneumatic cannon]], with a trigger chamber in between and a trigger [[valve]] that either dumps said chamber to the atmosphere, or connects it to the main chamber.

The burst disks must be dimensioned to break somewhere between half and full chamber [[pressure]]. The trigger chamber is filled to half the chamber pressure, and then the chamber is filled to full pressure. When the trigger valve is opened, one of the disks is subjected to the full chamber pressure and ruptures, in turn overloading and rupturing the second burst disk.

The design has the advantages of quick opening and full flow of a burst disk, and with the reliability and repeatability of normal [[pilot valve]]s. It has the other disadvantages of a burst disk system, as well as higher consumption of burst disks.

Implementations of this idea may be found here: [http://www.spudfiles.com/forums/triggered-burst-disk-by-pilgrimman-t12809.html] and here[http://www.spudfiles.com/forums/sctbdcv1-5-450psi-50mm-steel-cannon-updated-with-new-vid-t12103.html].

== Mechanically Induced Failure ==
Alternatively, the structural integrity of a single burst disk may be compromised, as by a broad head on a pneumatic ram or a resistive heating element embedded in the burst disk.

By damaging the burst disk, the bursting pressure of the disk decreases, until the pressure in the chamber is sufficient to destroy it.

[[category:valves]]

Triggered burst disk

2009-08-27T23:04:32Z

Boilingleadbath: + mechanical triggering

[[Image:Triggered_burstdisk.PNG|frame|The firing cycle of a triggered burst disk]][[Image:Triggeredburstdisk2.png|frame|An example of a mechanically triggered burst disk; for the purpose of the example, D is a broad head.]]
A triggered [[burst disk]] system allows the user to accurately control the time of firing, in one of two ways:

_Cascade Failure_
Cascade failure systems consist of two burst disks mounted between the [[chamber]] and [[barrel]] of a [[pneumatic cannon]], with a trigger chamber in between and a trigger [[valve]] that either dumps said chamber to the atmosphere, or connects it to the main chamber.

The burst disks must be dimensioned to break somewhere between half and full chamber [[pressure]]. The trigger chamber is filled to half the chamber pressure, and then the chamber is filled to full pressure. When the trigger valve is opened, one of the disks is subjected to the full chamber pressure and ruptures, in turn overloading and rupturing the second burst disk.

The design has the advantages of quick opening and full flow of a burst disk, and with the reliability and repeatability of normal [[pilot valve]]s. It has the other disadvantages of a burst disk system, as well as higher consumption of burst disks.

Implementations of this idea may be found here: [http://www.spudfiles.com/forums/triggered-burst-disk-by-pilgrimman-t12809.html] and here[http://www.spudfiles.com/forums/sctbdcv1-5-450psi-50mm-steel-cannon-updated-with-new-vid-t12103.html].

_Mechanically Induced Failure_
Alternatively, the structural integrity of a single burst disk may be compromised, as by a broad head on a pneumatic ram or a resistive heating element embedded in the burst disk.

By damaging the burst disk, the bursting pressure of the disk decreases, until the pressure in the chamber is sufficient to destroy it.

[[category:valves]]

Toolies Piston Valve

2009-08-27T22:50:16Z

Boilingleadbath: + cross section

[[Image:Wtooliepiston.png|frame|Cross-section of toolie-style piston valve; A is barrel, B is sealing face, C is chamber, D is drive rod, E is piston, F is pilot volume, G is pilot valve.]]
A '''toolies piston valve''' is a type of inline barrel-sealing [[piston valve]] which allows inline (or any) [[launcher configuration|configuration]] launcher setup with more effective chamber volume than a simple coaxial barrel-sealing piston valve.

==Inner Workings==
The toolie's type valve consists of an air chamber. At one end (the pilot end), a large piston sits which is the same diameter as the inside of the pipe. A long rod (threaded rod, smooth rod, pipe nipple, whatever) reaches all the way to the other side of the chamber, where it ends in a sealing face only marginally larger than the outside diameter of the barrel. This rod also usually has a spacer to center it in the air chamber.

When the pilot is exhausted, the piston will move back because of the force pushing against the other side of the larger piston, and against the small exposed area on the barrel-sealing piston. Like most barrel-sealers, there is a "jump" in force as the barrel-sealer unseats from the back of the barrel, and the piston moves backwards.

==Implementations==
[http://www.spudfiles.com/forums/valve-trouble-t14475.html Valve implementation by judgment_arms]

[http://my.freeway.net/~toolies/ The Original]

[[category:valves]]

Butterfly valve

2009-08-27T22:47:57Z

Boilingleadbath: + cross section

[[Image:Wbutterfly.png|frame|Cross-section of butterfly valve; A is barrel, B is seal, C is disk, and D is chamber. Note that sealing geometry is probably inaccurate.]]
[[Image:Butterfly_valve.jpg|frame|A typical butterfly valve]]
A '''Butterfly valve''' is a type of flow control device, used to make a fluid start or stop flowing through a section of pipe. The [[valve]] is similar in operation to a [[ball valve]]. A flat circular plate is positioned in the center of the pipe. The plate has a rod through it connected to a handle on the outside of the valve. Rotating the handle turns the plate either parallel or perpendicular to the flow of water, shutting off the flow. It is a very robust and reliable design. However, unlike the ball valve, the plate does not rotate out of the flow of water, so that a [[pressure]] drop is induced in the flow.

These valves are typically used in applications where a very large valve is needed, such as pumpkin chucking and dams, and are available on ebay in sizes from roughly 2" to 10+". These are very cheap, with a 4" metal valve often selling for 50-20$ or less. Unfortunately, most butterfly valves use bolts to attach to the pluming system, requiring one to buy a flanged [[adapter]] or use [[flange]]d metal pipe.

There are three types of butterfly valve:
# '''Resilient butterfly valve''' which has a flexible rubber seat. Working pressure up to 1.6 Mpa (232 psi)
# '''High performance butterfly valve''' which is usually double eccentric in design . Working pressure up to 5.0 Mpa (725 psi)
# '''Tricentric butterfly valve''' which is usually with metal seated design. Working pressure up to 10.0 Mpa (1450 psi)

== See also ==
* [[Ball valve]]
* [[Gate valve]]
* [[Globe valve]]

[[category:valves]]

Burst disk

2009-08-27T22:45:20Z

Boilingleadbath: + cross section

[[Image:Burstdisk.png|frame|Cross-section of burst disk in a union; A is chamber, B is barrel, C is the fragile disk, and D is the union.]]
A '''burst disk''' consists of a thin disc of airtight material that will rupture at a certain pressure, held in place inside a [[union]] or cam lever coupling. (See the [[burst disk material]] page.)

Since the burst disk ruptures almost instantly when the pressure gets to a certain point, they have the fastest [[opening time]] of any [[valve]] in existence. Since they are pressure-triggered they are nearly always used in [[hybrid cannon|hybrids]], they are also occasionally used as the main valve in a [[pneumatic cannon]] because of their superior performance. Sometimes they are used as a secondary valve in a [[pneumatic cannon]] to compensate for the slower opening time of the main valve.

Burst disks are a very close rival to a [[ball valve]] in cost, at roughly $13 for a 2" [[union]] in sch 40 PVC. More expensive (but convenient) devices exist, such as [[camlock coupling]]s.

To use, [[solvent welding|solvent weld]] your chamber to one half of your union or cam coupling. One then 'loads' the valve by putting one or more layers of [[burst disk material]] (such as aluminum foil, or a piece of a beverage container) in between the two halves of the union or coupling. The union or cam coupling is then tightened down, locking the burst disk in place.

In a hybrid cannon, burst disks fail when the pressure builds due to the combusting gases. Prior to this, the chamber was containing the flammable gases at a relatively low pressure. They are also sometimes used on [[combustion cannon]]s - for their noisemaking capabilities, and/or their ([http://www.advancedspuds.com/burstdisk.htm debated]) performance improvement.

In a pneumatic cannon, they can be used in the same way, simply pointing the cannon in the correct direction and filling it until it fires. However, many opt to use another system because of the inherent safety issues with this. Such systems include puncturing it with a pointy object (such as a nail) attached to the end of the projectile, melting it with an electrically heated wire, or having a pneumatically [[triggered burst disk]] system using dual burst disks.

Since Burst disks only last for a single shot and need to be replaced before each round, [[Burst Disk Cartridge]]s (BDC) have been created.

[[category:valves]]

Ball valve

2009-08-27T22:42:24Z

Boilingleadbath: forgot lable descriptions for cross-section

[[Image:Wballvalve.png|frame|Cross-section of typical ball valve; A is barrel, B is ball, C is handle (not actually in the plane of the cut), D is chamber]]
[[Image:Ball_valve.jpg|frame|A photo of a typical PVC ball valve]]
'''Ball valves''' open with a 90* twist of lever, similar to the operation of a [[butterfly valve]]. They are about the cheapest [[valve]] you can get, but also (typically) yield the worst performance, due to the slow [[opening time]].
The flow of a ball valve, however, is quite good due to its straight-through nature. This will tend to even out the situation in cannons with very long [[barrel]]s and/or heavy projectiles (and thus long barrel dwell times).

Opening time can be shortened by:
* Using a spring or a pneumatic ram to actuate the valve
* Applying dish soap or other lubricant to the moving part. Oil or oil based lubricants should ''not'' be used, because they can damage the seals. Lubricating the ball valve will decrease friction and will result in a faster opening time.

However, there is more performance to be gained by using a faster valve, such as a butterfly valve, [[piston valve|piston]] or [[diaphragm valve]], or a [[burst disk]].

It is possible to achieve extremely low opening times with ball valves through somewhat unconventional methods. Unfortunately, to open in the time necessary to make it a practical valve, a rather large amount of energy must be applied - so much, in fact, that in the lone test this was actually tried, the kinetic energy of the handle completely demolished the valve, and the ram was never recovered. This only serves to prove that you really are better off with a faster valve.

[[category:valves]]

Ball valve

2009-08-27T22:41:06Z

Boilingleadbath: + internal diagram

[[Image:Wballvalve.png|frame|Cross-section of typical ball valve]]
[[Image:Ball_valve.jpg|frame|A photo of a typical PVC ball valve]]
'''Ball valves''' open with a 90* twist of lever, similar to the operation of a [[butterfly valve]]. They are about the cheapest [[valve]] you can get, but also (typically) yield the worst performance, due to the slow [[opening time]].
The flow of a ball valve, however, is quite good due to its straight-through nature. This will tend to even out the situation in cannons with very long [[barrel]]s and/or heavy projectiles (and thus long barrel dwell times).

Opening time can be shortened by:
* Using a spring or a pneumatic ram to actuate the valve
* Applying dish soap or other lubricant to the moving part. Oil or oil based lubricants should ''not'' be used, because they can damage the seals. Lubricating the ball valve will decrease friction and will result in a faster opening time.

However, there is more performance to be gained by using a faster valve, such as a butterfly valve, [[piston valve|piston]] or [[diaphragm valve]], or a [[burst disk]].

It is possible to achieve extremely low opening times with ball valves through somewhat unconventional methods. Unfortunately, to open in the time necessary to make it a practical valve, a rather large amount of energy must be applied - so much, in fact, that in the lone test this was actually tried, the kinetic energy of the handle completely demolished the valve, and the ram was never recovered. This only serves to prove that you really are better off with a faster valve.

[[category:valves]]

File:Wtooliepiston.png

2009-08-27T22:39:09Z

Boilingleadbath: A 'Toolie-format' barrel-sealing piston valve.

A 'Toolie-format' barrel-sealing piston valve.

File:Wballvalve.png

2009-08-27T22:38:07Z

Boilingleadbath: A ball valve. Design proportions are somewhat nonstandard.

A ball valve. Design proportions are somewhat nonstandard.

File:Wquickdump.png

2009-08-27T22:37:01Z

Boilingleadbath: A 'quick dump' style valve.

A 'quick dump' style valve.

File:Wbutterfly.png

2009-08-27T22:36:35Z

Boilingleadbath: A butterfly valve. Details of sealing surface are most certainly inaccurate - intended to show flow and general design only.

A butterfly valve. Details of sealing surface are most certainly inaccurate - intended to show flow and general design only.

File:Triggeredburstdisk2.png

2009-08-27T22:35:46Z

Boilingleadbath: A burst disk triggered by a sharp.

A burst disk triggered by a sharp.

File:Burstdisk.png

2009-08-27T22:34:45Z

Boilingleadbath: Burstdisk in standard, non actuated, use.

Burstdisk in standard, non actuated, use.

Spudgun accuracy

2007-07-26T19:17:34Z

Boilingleadbath: New page: ''Accuracy'' is a measure of how consistently a gun shoots; an accurate gun shoots in the same position relative to where the gun was aimed. The various causes of inaccuracy in spudguns a...

''Accuracy'' is a measure of how consistently a gun shoots; an accurate gun shoots in the same position relative to where the gun was aimed.

The various causes of inaccuracy in spudguns are probably the same as those in firearms, though are of unknown importance:
#The flexing of the [[barrel]], which results in the projectile leaving in the wrong direction or velocity.
#The movement of the launcher under recoil.
#The tumbling and resulting aerodynamic lift forces on the projectile.
#In [[rifled barrel]]s, the spin throwing the projectile off of the intended path due to the center-of-mass not being in the center of the projectile.
#The muzzle blast deflecting the projectile.

The first problem can be minimized by stiffening the barrel; this can be accomplished one of two ways:
#By shortening the barrel.
#By stiffening the barrel - either by using metal pipe, using larger diameter pipe, [[sleeving]] the barrel, or using some sort of reenforcement.

The second effect cannot be eliminated, but it's negative effects can be mitigated by allowing the launcher to recoil the same on every shot.

The third effect [http://www.burntlatke.com/rifle.html seems] to be one of the main ones, as spinning the projectiles reduced group sizes by about 50%. Alternative fixes exist, including:
*Using round munitions, which cannot generate lift unless they are spinning.
*Fin-stabilizing the ammunition.

The fourth effect is probably not very significant, even given the large variations in the location of the center of mass in cut potatoes, but can be reduced in severity by using as low a twist rate as possible as well as cutting the potatoes such that their COM is inline with the center of the bore.

The fifth effect can be reduced by [[porting]] the barrel.

[[Category: Concepts]]

Rifled barrel

2007-07-26T18:29:32Z

Boilingleadbath: + greenhil

In order to more accurately send a vegetable projectile towards the desired target, barrels for produce accelerators can be "rifled" which produces spiral grooves on the inside surface of the barrel.

These grooves impart rotation to the projectile as it accelerates down the barrel, gyroscopically stabilizing it and preventing the projectile from tumbling end-over-end. This spinning motion has been demonstrated to have positive effects accuracy of potatoes, as seen in [http://www.burntlatke.com/rifle.html this] test done by the [[burnt latke]] group.

The rate of twist required can be approximated through a version of the Greenhill equation that has been modified to take into account the density of the projectile, though one must remember that the Greenhill equation was developed to deal with supersonic, pointed, and very dense projectiles:
Twist = (C*D2)/L * sqrt(SG/10.9)

where:
*Twist = number of inches per rotation
*C = 150 (use 180 for muzzle velocities higher than 2,800 f/s)
*D = bullet's diameter in inches
*L = bullet's length in inches
*SG = bullet's specific gravity

Rates of twist higher than this should not hurt accuracy much, unless they break off the bits of potato that are engaging the rifling and thusly transmit no rotation at all.

Rifled barrels are available from the [[SGTC]].

See also [[spudgun accuracy]]

[[Category:Components]]

Piston valve

2007-07-26T17:58:59Z

Boilingleadbath: + chamber sealers

A '''piston valve''' is a [[pilot valve|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|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-rings. 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|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 air to hold the valve shut, rather than using the force of the air.

[[category:valves]]

File:Wcspiston.PNG

2007-07-26T17:45:07Z

Boilingleadbath: An explanation of the operation of a chamber-sealing piston valve.

An explanation of the operation of a chamber-sealing piston valve.

12 gram CO2 cartridge

2007-05-30T12:45:11Z

Boilingleadbath: formatting

12 gram '''CO2 cartridges''' are used primarily as a portable way to provide pressurized gas to a [[pneumatic cannon]]. They cost roughly $0.50 a peice, and are typically connected via an adapter, which can be purchased for about $10 USD.
Once empty, they are often used as projectiles - they have a high mass, are quite sturdy, and fit in 3/4" SCH. 40 PVC.

The following is a chart outlining the chamber size (in cubic inches) vs. pressure in (pounds per square inch) using a 12 gram CO2 cartridge:
<table>
<tr><td>Chamber Size (ci)</td><td>Chamber Pressure (PSI)</td></tr>
<tr><td>10</td><td>420</td></tr>
<tr><td>20</td><td>210</td></tr>
<tr><td>30</td><td>140</td></tr>
<tr><td>40</td><td>105</td></tr>
<tr><td>50</td><td>84</td></tr>
<tr><td>60</td><td>70</td></tr>
<tr><td>70</td><td>60</td></tr>
<tr><td>80</td><td>53</td></tr>
<tr><td>90</td><td>47</td></tr>
<tr><td>100</td><td>42</td></tr>
</table>

To calculate the pressure for any non-given value, use this equation, but note that the pressure can't go above 800 PSI (the vapor pressure of CO2).

4200/Chamber Volume In ci=Chamber Pressure in psi -OR- 4200/CV=CP 
For example: 
You have a chamber volume of 41.3ci. 
So it can be said that 4200/41.3=CP 
4200/41.3 is equal to 101.6949152542373 For simplicity's sake we will round this to 101.7 
This means that CP=101.7 PSI 
Your 41.3ci chamber will have a pressure of 101.7 PSI when filled with one 12g CO2 cartridge. 

[[category:Accessories]]

Schrader valve

2007-05-14T21:19:42Z

Boilingleadbath: mounting meathods

A '''schrader''' valve, often called a "tire valve", "tank valve" or "sniffler valve" because schrader is a brand name, is used in [[hybrid launcher|hybrid]] and [[pneumatic launcher]]s to allow you to fill them with air. They are also used, less frequently, in [[combustion launcher]]s, to allow you to [[venting|vent]] them.

These valves can be mounted in various ways, depending on the sub-variety that you purchase: 
1) Threaded into a [[tapping | tapped]] hole. 
2) Clamped on both sides of the workpiece (as with some automotive valves). 
3) Epoxied in place (as with weird or salvaged valves). 

They accept the standard air chuck used to fill tires, allowing you to fill them with a standard bicycle pump.
Alternative valves exist, most notably the [[quick disconnect]] which is more expensive, but has a higher amount of flow.

[[Image:Schrader.jpg‎‎]]

[http://en.wikipedia.org/wiki/Schraeder_valve more info]

[[category:valves]]

Schrader valve

2007-05-14T21:19:00Z

Boilingleadbath: + mounting

A '''schrader''' valve, often called a "tire valve", "tank valve" or "sniffler valve" because schrader is a brand name, is used in [[hybrid launcher|hybrid]] and [[pneumatic launcher]]s to allow you to fill them with air. They are also used, less frequently, in [[combustion launcher]]s, to allow you to [[venting|vent]] them.

These valves can be mounted in various ways, depending on the sub-variety that you purchase:
1) Threaded into a [[tapping | tapped]] hole.
2) Clamped on both sides of the workpiece (as with some automotive valves).
3) Epoxied in place (as with weird or salvaged valves).

They accept the standard air chuck used to fill tires, allowing you to fill them with a standard bicycle pump.
Alternative valves exist, most notably the [[quick disconnect]] which is more expensive, but has a higher amount of flow.

[[Image:Schrader.jpg‎‎]]

[http://en.wikipedia.org/wiki/Schraeder_valve more info]

[[category:valves]]

Tapping

2007-05-14T21:14:35Z

Boilingleadbath: +external link

[[Image:Tap_set.gif|right|thumb|250ps|A set of pipe taps]]'''Tapping''' is the process of cutting [[thread]]s on the inside diameter of a hole with a tool called a tap. It is used to thread holes for mounting:
*[[Pressure gauge]]s
*[[Fuel meter]]s
*Electrodes (Bolts)
*[[Safety valve]]s
*Other

==='''Types of Threads'''===

There are a few diffent thread systems that are used in spudgun construction

*NPT (National Pipe Taper)
*BSP (British Standard Pipe)
*NF (National Fine)
*NC (National Course)

==='''The Process'''===

#Mark and drill an appropriatly sized hole
#*The hole should be in an area where fittings or pipe overlap (double thickness)[[Image:ReltonRapidTap.jpg|right|thumb|An appropriate cutting fluid for tapping holes. It is usually available at tool stores. ]]
#*Find correct hole size with a [http://www.engineersedge.com/tap_drill_chart.htm Tap/Drill Chart]
#Insert the tap into the tap wrench
#*If you don't have a tap wrench, a normal crescent wrench can be used
#Cut the threads
#*Be careful to keep the tap straight or you will end up with crooked threads
#*When tapping plastic (or any other material) be sure to use an appropriate [http://www.relton.com/html/cutfluid2003.html cutting fluid] such as RapidTap® made by [http://www.relton.com/ Relton].
#*Apply downward pressure while slowly turning the tap clockwise 180 degrees, then back out 90 degrees counterclockwise to clear the chips
#*For tapered threads, stop as soon as the entire length of the hole is threaded

== external links ==
[http://www.wikihow.com/Use-a-Tap wikihow's article on tapping]
[[Category:Construction methods]]

EVBEC

2007-04-16T13:13:31Z

Boilingleadbath: formatting

EVBEC stands for "Energy & Volume Based Estimator for Combustions", and is intended to calculate the muzzle velocity of [[combustion launcher]]s.
The latest version of the spreadsheet (V 1.5) can be downloaded from [[spudfiles]] [http://www.spudfiles.com/forums/viewtopic.php?t=1212& here]
A web-based version written in javascript, which is significantly more user freindly, is hosted [http://www.spudfiles.com/EVBEC/JSE.html here].

==Physics model==
EVBEC assumes the following is true:
*Energy produced from combustion is directly proportional to chamber volume TIMES the chamber pressure in absolute terms.
*The portion of this energy utilized in a launcher is directly related to the [[Chamber to barrel ratio]].
*The [http://www.burntlatke.com/launch.html latke tests] are accurate.
*The amount of energy required to displace the air in the barrel is porportional to the atmospheric pressure*volume.
*The amount of eneryg 'stolen' by the velocity of the gasses origionaly in the barrel can be found by mass*(average velocity), and that this hteft can be modeled as adding their effective mass to the projectile's mass.
*The amount of energy 'stolen' by the velocity of the propellent gasses can be is equal to their masses times their average velocities at projectile exit, and that this theft can be modeled as adding their effective mass to the projectile's mass.

To calculate the velocities, EVBEC uses a 2 step procces:
0) Take the muzzle velocity of the round found in the latke C:B test at the same ratio 
1) We find the energy of the test projectile, add the energy required to displace the air in the barrel, multiply this by the compression ratio, subtract the displacement energy, and convert it back into a velocity. 
2) We find the ratio of the modeled launcher's chamber size to the test launcher's, multiply this by the ratio of the test launcher's projectile mass (including effective propellent masses) to the test launcher's projectile mass (including their effective propellent masses).

===differences between spreadsheet and javascript versions===

In the spreadsheet, the velocities are calculated for all the ratios and barrel diameters tested by [[latke]], and the proper ratio to use to find the velocity is indicated on a graph. This uses the actual dataset.

In the javascript version, the velocity is calculated using a curve fit of the 3/4" data, and the velocity is output as a number in a cell.

==limits of the physics model==
The physics model does not account for the following:
*Differing burn times
*Differing amounts of heat loss
*Evaporation of tater juices
*Differing amounts of friction
*Variations in efficiency caused by different projectile masses. (which is probably why the 1.5" data is "out there")
*Odd effects caused by launcher design (ie; breach restrictions).

==use==
Generic directions for use are provided in the documentation of the spreadsheet, and a detailed artical on modeling combustion spudguns, mostly with EVBEC spreadsheet, is provided [http://www.spudfiles.com/forums/viewtopic.php?t=5966& here].
The javascript version has many tooltips and is fairly self explanatory.

[[category:Concepts]]

EVBEC

2007-04-16T13:12:28Z

Boilingleadbath: updated it to account for V1.5

EVBEC stands for "Energy & Volume Based Estimator for Combustions", and is intended to calculate the muzzle velocity of [[combustion launcher]]s.
The latest version of the spreadsheet (V 1.5) can be downloaded from [[spudfiles]] [http://www.spudfiles.com/forums/viewtopic.php?t=1212& here]
A web-based version written in javascript, which is significantly more user freindly, is hosted [http://www.spudfiles.com/EVBEC/JSE.html here].

==Physics model==
EVBEC assumes the following is true:
*Energy produced from combustion is directly proportional to chamber volume TIMES the chamber pressure in absolute terms.
*The portion of this energy utilized in a launcher is directly related to the [[Chamber to barrel ratio]].
*The [http://www.burntlatke.com/launch.html latke tests] are accurate.
*The amount of energy required to displace the air in the barrel is porportional to the atmospheric pressure*volume.
*The amount of eneryg 'stolen' by the velocity of the gasses origionaly in the barrel can be found by mass*(average velocity), and that this hteft can be modeled as adding their effective mass to the projectile's mass.
*The amount of energy 'stolen' by the velocity of the propellent gasses can be is equal to their masses times their average velocities at projectile exit, and that this theft can be modeled as adding their effective mass to the projectile's mass.

To calculate the velocities, EVBEC uses a 2 step procces:
0) Take the muzzle velocity of the round found in the latke C:B test at the same ratio
1) We find the energy of the test projectile, add the energy required to displace the air in the barrel, multiply this by the compression ratio, subtract the displacement energy, and convert it back into a velocity.
2) We find the ratio of the modeled launcher's chamber size to the test launcher's, multiply this by the ratio of the test launcher's projectile mass (including effective propellent masses) to the test launcher's projectile mass (including their effective propellent masses).

===differences between spreadsheet and javascript versions===

In the spreadsheet, the velocities are calculated for all the ratios and barrel diameters tested by [[latke]], and the proper ratio to use to find the velocity is indicated on a graph. This uses the actual dataset.

In the javascript version, the velocity is calculated using a curve fit of the 3/4" data, and the velocity is output as a number in a cell.

==limits of the physics model==
The physics model does not account for the following:
*Differing burn times
*Differing amounts of heat loss
*Evaporation of tater juices
*Differing amounts of friction
*Variations in efficiency caused by different projectile masses. (which is probably why the 1.5" data is "out there")
*Odd effects caused by launcher design (ie; breach restrictions).

==use==
Generic directions for use are provided in the documentation of the spreadsheet, and a detailed artical on modeling combustion spudguns, mostly with EVBEC spreadsheet, is provided [http://www.spudfiles.com/forums/viewtopic.php?t=5966& here].
The javascript version has many tooltips and is fairly self explanatory.

[[category:Concepts]]

Gas Gun Design Tool

2007-04-15T12:51:49Z

Boilingleadbath: categorized

Hall Consulting's '''Gas Gun Design Tool''' is a simulation program to aid the design of [[pneumatic cannon]]s. It is available [http://www.thehalls-in-bfe.com/GGDT here].

==Physics model==
As of version 4.2, in modeled the following features:

# Valve configuration and opening times. In fact, GGDT models five different types of valve: chamber sealing pilot (see [[piston valve]]s), barrel sealing pilot (ie, barrel sealing [[diaphragm valve]]s and [[piston valve]]s, [[burst disk]], [[hammer valve]], and "generic." Each of these valves have different behaviors and GGDT accounts for these behaviors (more on that below).
# Pressure drop across the valve oriface.
# Temperature (and thus pressure) increase in the valve pilot due to work performed by gun gases on the valve piston/diaphragm.
# Gas leakage from the main valve body into the upper valve chamber ([[pilot]]).
# Performance differences due to different gases.
# Temperature effects on gas properties (and thus, performance).
# Performance limitations due to flow choking in the valve or the barrel.
# Valve effective oriface increases due to lowered valve throat Mach number.
# Temperature (and thus pressure) drop in the barrel due to work performed by the gas accelerating the projectile.
# Gas leakage around the projectile in the barrel.
# Compressibility (Mach) effects on air pressure both in front of and behind the projectile to include the creation of shocks. (see [[shock heating]])

However, it does not consider:

# Energy losses associated with turbulence or frictional forces between the gas and the gun's reservoir/barrel walls. In other words, pressure drops due to bends or rough edges in the gun's plumbing.
# Reservoir fineness ratio's effect on performance.
# Freezing or liquification of gun gases.

However, these are not a major concern in most launchers, as they require very long barrels or very high pressures to notice.
Typically, the GGDT outputs numbers within 5-10% of the measured value, although this is somewhat clouded by not knowing the proper input numbers.

==Use==
See Hall's [http://www.thehalls-in-bfe.com/GGDT page] on use

{{stub}}
[[category:Concepts]]

Category:Website use

2007-04-15T12:49:43Z

Boilingleadbath: new

How to use the wiki and the forums.

SpudFiles forum guidelines

2007-04-15T12:46:55Z

Boilingleadbath: categorized

The following is documentation pertaining to the [http://www.spudfiles.com/ SpudFiles] forum.

[[How-To]]

[[Rules/ Suggestions]]

[[Forum Code]]

[[category:Website use]]

How-To

2007-04-15T12:45:53Z

Boilingleadbath: categorized

==Posting a image:==
First it must be determined if the image is already hosted on the internet, or if it is on your computer hard drive.

'''Image is hosted:'''

First right-click the desired image, then select 'Copy image location'. If not available, select 'Properties'. Listed will be the 'location', highlight, and [[copy]] the location. The location must then be put in tags. Either of the following will work:
* [img]''<nowiki>http://www.spudfiles.com/forums/templates/DAJ_Glass/images/logo.gif</nowiki>''[/img]
* <img src="''<nowiki>http://www.spudfiles.com/forums/templates/DAJ_Glass/images/logo.gif</nowiki>''">
[The location - ''<nowiki>http://www.spudfiles.com/forums/templates/DAJ_Glass/images/logo.gif</nowiki>'' - was used as a example.]

'''Image on hard drive:'''

If you are writing a reply, first select the 'Add Reply' button. Once you have added your remarks, scroll down to 'add an attachment'. Under 'Filename' select browse, and find the image on your computer. At this time if your so choose add a description for the image, then select 'Add Attachment'. This may be done multiple times before 'Submitting'.

[[category:Website use]]

Forum Code

2007-04-15T12:43:34Z

Boilingleadbath: categorization woops fix

SpudFiles accepts both basic BBCode, and HTML. These markup languages can be used in your posts, and responses.

{| class="wikitable"
| style="text-align: center" | '''BBCode'''
| style="text-align: center" | '''HTML'''
| style="text-align: center" | '''Effect'''
|-
| <code><nowiki>[b]bolded text[/b]</nowiki></code>
| <code><nowiki>bolded text</nowiki></code>
| '''bolded text'''
|-
| <code><nowiki>[i]italicized text[/i]</nowiki></code>
| <code><nowiki>italicized text</nowiki></code>
| ''italicized text''
|-
| <code><nowiki>[u]underlined text[/u]</nowiki></code>
| <code><nowiki>underlined text</nowiki></code>
| underlined text
|-
| <code><nowiki>[url]http://wikipedia.org[/url]</nowiki></code>
| <code><nowiki><a href="http://wikipedia.org"> http://wikipedia.org</a></nowiki></code>
| [http://wikipedia.org http://wikipedia.org]
|-
| <code><nowiki>[url=http://wikipedia.org]Wikipedia[/url]</nowiki></code>
| <code><nowiki><a href="http://wikipedia.org">Wikipedia</a></nowiki></code>
| [http://wikipedia.org Wikipedia]
|-
| <code><nowiki>[img]http://upload.wikimedia.org/wikipedia/
commons/thumb/6/63/Wikipedia-logo.png/
150px-Wikipedia-logo.png[/img]</nowiki></code>
| <code><nowiki><img src="http://upload.wikimedia.org/wikipedia/
commons/thumb/6/63/Wikipedia-logo.png/
150px-Wikipedia-logo.png" /></nowiki></code>
| [[Image:Wikipedia-logo.png|150px]]
|-
| <code><nowiki>[quote]quoted text[/quote]</nowiki></code>
| <code><nowiki><blockquote>quoted text</blockquote></nowiki></code> (usually implemented in more advanced ways)
| To quote:<blockquote>quoted text</blockquote>
|-
| <code><nowiki>[code]monospaced text[/code]</nowiki></code>
| <code><nowiki><pre>monospaced text</pre></nowiki></code>
| <code>monospaced text</code>
|-
| <code><nowiki>[size=15]Your Text[/size]</nowiki></code> ("12" is usually standard on message boards. Usually measured in pixels (px))
| <code><nowiki>Your Text</nowiki></code>
| Your Text
|-
| <code><nowiki>[color=red]Red Text[/color]</nowiki></code> or 
<code><nowiki>[color=#FF0000]Red Text[/color]</nowiki></code> (Can use many different color names or hex codes.)
| <code><nowiki>Red Text</nowiki></code>
|Red Text
|-
| <code><nowiki>[:-)] </nowiki></code>(Not always enclosed in brackets.) or 
<code>:smile:</code>

(And usually other [[emoticon]]s)
| <code><img src="Face-smile.gif" alt="" /></code>
| [[Image:Face-smile.svg|24px]]

(Specific image and size vary)
|}

[[category:Website use]]

Copy

2007-04-15T12:42:25Z

Boilingleadbath: categorized

Right-click> select 'copy'

-OR-

Keyboard function: Ctrl+C

[[category:Website use]]

Forum Code

2007-04-15T12:41:09Z

Boilingleadbath: categorized

Category:Ignition sources:Camera Flash

2007-04-15T12:39:47Z

Boilingleadbath: new

These are all stubs, and should probably be condensed into one article.

Category:Concepts

2007-04-15T12:38:33Z

Boilingleadbath: new

This category should include useful ideas and programs, but not information on actually building the things.

Step 6 - Providing Power to the Relay

2007-04-15T12:35:50Z

Boilingleadbath: categorized

<h3>Providing Power to the Relay</h3> 
 [[Image:Camera_Flash_5.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

What is a spudgun?

2007-04-15T12:35:08Z

Boilingleadbath: dubiously categorized

'''Spud guns''', '''potato cannons''', '''produce accelerators''', or '''weapons of mashed destruction''' are all recreational launching devices usually made of plumbing pipe. There are two common means to launch projectiles from a spudgun. The [[pneumatic launcher|first]] uses the energy stored in a compressed gas and the [[combustion launcher|second]], more popular method, uses the energy released by combusting fuel vapors to heat the air and cause it to expand. There is a quite rare mix of the two, a [[hybrid launcher|"hybrid"]], that combusts a pressurized fuel-air mixture. The object of these varieties is to propel projectiles in the direction of a designated (safe) target for fun. Common [[catogory:projectile|projectile]]s include: [[mandarin orange|mandarins]], [[potato]]es, [[tennis ball]]s, [[golf ball]]s,bb's (if you have a small enough barrel), in fact pretty much any spare vegetable you can ram down the tube. This makes them a particularly popular home-made class of projectile launchers because of their low cost to build: a simple static-guard powered gun costs no more than $20 in PVC and glue, less if parts can be scrounged.

Please see the article on [[safety]].

[[category:Concepts]]

Stoichiometry

2007-04-15T12:33:57Z

Boilingleadbath: categorized

[http://en.wikipedia.org/wiki/Stoichiometric Stoichiometry] is an important concept in [[combustion cannon|combustion]] and [[hybrid cannon|hybrid]] launchers, since they use the energy from combustible fuels. A stoichiometric mixture is one where the ratio of fuel and oxygen molecules is balanced, so all the fuel and oxygen in the chamber is (in optimal conditions) consumed in the reaction. A [[fuel meter]] system is usually designed to achieve this mixture, which will yield the most power out of the combustion reaction.

===Calculations===

The stoichiometric ratio for gaseous fuels can easily be calculated. When the hydrogen and carbon in a fuel burns, it combines with oxygen as follows:

C + O2 --> CO2 
2H2 + O2 --> 2H2O 
CxHx + O2 --> CO2 + H2O

If the fuel molecule contains oxygen atoms, they will replace oxygen atoms from the air in the reaction. So for each oxygen atom the fuel contains, one less atom of atmospheric oxygen is needed. To begin calculating the stoichiometric ratio of a fuel, first find the chemical formula for the fuel, and count how many hydrogen, carbon and oxygen (if any) atoms it contains.

Since hydrogen combines with oxygen to make water (H2O), and two hydrogen atoms combine with every oxygen atom, four hydrogen atoms will consume one O2 molecule. Conversely, it can be said that one hydrogen atom will consume 0.25 O2 molecules.

Carbon atoms combine with oxygen to form CO2, so each carbon atom will consume one entire O2 molecule.

Any oxygen in the fuel will lead to one less oxygen atom being consumed from the air. Two oxygen atoms will prevent one O2 molecule from being consumed, so each oxygen atom "saves" 0.5 O2 molecules.

Now we need to find how many O2 molecules are consumed by each fuel molecule, which is calculated as follows:
*for each hydrogen atom, add 0.25 to the amount of oxygen molecules needed
*for each carbon atom, add 1
*for each oxygen atom, subtract 0.5
The resulting number is the oxygen to fuel ratio. To find the fuel to oxygen ratio, divide 1 by this number. The amount of oxygen in air is 21%, so to find the fractional fuel to air ratio, the fuel to oxygen ratio is multiplied with 0.21. To find the ratio in percent, multiply this value by 100.

To find the volume of fuel needed for a particular chamber, the fractional ratio is multiplied by the chamber volume.

===Concrete example===

Formula of [[propane]]: C3H8

*number of carbon molecules: 3
*number of hydrogen molecules: 8
*number of oxygen molecules: 0

number of oxygen molecules needed = 3*1 + 8*0.25 = 5 molecules 
the actual combustion reaction is as follows: C3H8 + 5O2 --> 3CO2 + 4H2O

fuel/oxygen ratio = 1/5 = 0.2 
fuel/air ratio = 0.2*0.21 = 0.042, or 4.2% 
fuel volume in a 3000 cc chamber = 3000*0.042 = 126 cc

Single formula for fractional fuel to air ratio: (1/(C+(H/4)+(O/2)))*0.21

[[category:Concepts]]

Step 9 - Replacing the Charging Button

2007-04-15T12:33:07Z

Boilingleadbath: categorized

<h3>Replacing the Charging Button</h3>
 
 [[Image:Camera Flash - Alternate Charge Switch.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 8 - Adding a Battery Holder and Kill Switch

2007-04-15T12:32:16Z

Boilingleadbath: categorized

<h3>Adding a Battery Holder and Kill Switch</h3>
 
 [[Image:Camera Flash - Battery Holder and Kill Switch 2.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 7 - Removing the Battery Contacts

2007-04-15T12:31:41Z

Boilingleadbath: categorized

<h3>Removing the Battery Contacts</h3>
 
 [[Image:Camera_Flash_-_Battery_Holder_and_Kill_Switch.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap

2007-04-15T12:31:06Z

Boilingleadbath: categorized

<h3>Adding the Ignition Coil and Spark Strip/Spark Gap</h3> 
 [[Image:Camera_Flash_4.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 4 - Adding the Relay

2007-04-15T12:30:32Z

Boilingleadbath: categorized

<h3>Adding The Relay</h3> 
 [[Image:Camera Flash 3.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 3 - Before Adding the Relay

2007-04-15T12:29:42Z

Boilingleadbath: categorized

<h3>Before Adding the Relay</h3> 
 [[Image:Camera_Flash_2.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 2 - Drilling the Holes for the Ignition Coil Wires

2007-04-15T12:29:09Z

Boilingleadbath: categorized

<h3>Drilling the Holes For the Ignition Coil Wires</h3>
Note: You can also just wrap the wires around the leads of the capacitor and apply solder to keep them on.
 
 [[Image:Camera_Flash_1.JPG]]
{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Step 1 - Removing the Flash Bulb

2007-04-15T12:28:14Z

Boilingleadbath: categorized

<h3>Removing the Flash Bulb</h3>Note: it is also not necessary to remove the bulb. You can also cut one lead and leave it attached to the board. The end result is the same.
 
 [[Image:Camera_Flash_0.JPG]]

{{Navbox
| name = Step 1 - Removing the Flash Bulb
| title = Installing a Camera Flash ignition
| body =
[[Step 1 - Removing the Flash Bulb|Step 1]] ·
[[Step 2 - Drilling the Holes for the Ignition Coil Wires|Step 2]] ·
[[Step 3 - Before Adding the Relay |Step 3]] ·
[[Step 4 - Adding the Relay |Step 4]] ·
[[Step 5 - Adding the Ignition Coil and Spark Strip/Spark Gap|Step 5]] ·
[[Step 6 - Providing Power to the Relay|Step 6]] ·
[[Step 7 - Removing the Battery Contacts|Step 7]] ·
[[Step 8 - Adding a Battery Holder and Kill Switch|Step 8]] ·
[[Step 9 - Replacing the Charging Button|Step 9]] ·
}}

{{stub}}
[[category:Ignition sources:Camera Flash]]

Spark strip

2007-04-15T12:26:10Z

Boilingleadbath: categorized

[[Image:Spark_strip.jpg|frame|An etched copper spark strip]]A '''spark strip''' is used to provide multiple sparks to ignite the fuel/air mix in a [[combustion launcher]]. It is differs from multiple [[spark gap]]s in that a spark strip is mounted using two or even one [http://www.advancedspuds.com/his.htm (temp link)] hole. This is done primarily to ensure the integrity of the launcher, as drilling multiple holes weakens the chamber. Spark strips can also be used in [[coaxial]] launchers, where chamber space is more cramped.

A spark strip consists of several conductive objects in a row with a short gap in between, effectively forming a line of spark gaps. As with other spark gaps, the combined width of the gaps must be small enough for the [[ignition source]] to overcome.

There are several ways to achieve this:
===scratched conductive film===
By scratching thin lines across a conductive film (metallic paints, CDs) it is possible to get very large numbers of sparks out of a meager scource. A more sophisticated method consists of etching a spark strip pattern in a printed circuit board.

===wire method===
Small pieces of wire, BBs, nuts or other metallic objects are attached to the chamber wall. (either directly or indirectly).

===veroboard===
Veroboard is a ready-made circuit board with multiple copper strips or dots, a piece cut perpendicular to the copper strips will function as a spark strip.

[[category:Components]]

Spark gap

2007-04-15T12:24:28Z

Boilingleadbath: categorized

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 cannon|combustion]] and [[hybrid cannon]]s. Spark gaps are normally made by screwing two bolts through the side wall of the chamber, at an angle that puts the tips of the screws close together. The screws should be mounted to keep the heads a good distance apart, to ensure that the spark will not jump between the heads outside the chamber. The distance must be small enough that the voltage from the ignition source can jump across it. The distance is about 1.1 mm/kV, this varies with the shape of the electrodes though, sharp points allow longer sparks than flat surfaces. It should be noted that the pressurized mixture of a hybrid will shorten the max spark length, so a hybrid spark gap should be a fair bit smaller than max spark length to ensure reliability.
Spark plugs can be used for spark gaps, and are especially useful in metal guns, where the chamber wall would short out the screws of an ordinary spark gap.
Two or more spark gaps can be connected in series to generate multiple sparks, as long as the width of the combined gaps is smaller than the maximum spark distance. Spark gaps can not be wired in parallel, since the spark will then only jump the smallest gap.
[[Spark strip]]s are a popular method of achieving multiple spark gaps.

[[category:Concepts]]
[[category:Components]]
[[category:Ugly]]

Shock heating

2007-04-15T12:23:04Z

Boilingleadbath: categorized

'''Shock heating''' is a proposed explanation for supersonic velocities in certain high-performance precharged [http://www.pyramydair.com/cgi-bin/model.pl?model_id=379 air rifles], because it is impossible for ambient temperature air to accelerate a projectile to faster than the speed of sound.

In shock heating, which only occurs at or slightly above the speed of sound in the gas, the flow of gas in the barrel essentially trades pressure for heat. The now heated gas has a higher speed of sound, allowing it to reach a higher velocity.

Although it is suspected that this shock heating occurs in a large number of weak shocks, or even a continuous 'shock volume', in the current versions of the [[GGDT]] physics model it is modeled as a single strong shock immediately behind the projectile. This is done to keep computation time reasonable, and produces fairly accurate predictions.

Although successful, it's [http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=13463 disputed] if it's the correct interpretation of the phenomenon.

== sources ==

[http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=13463 New explanation]

[http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=8265 Original thread on shock heating]

[http://www.spudfiles.com/spudtech_archive/viewtopic.php?t=8365 Second thread on shock heating]

[[category:Concepts]]

Safety

2007-04-15T12:22:29Z

Boilingleadbath: categorized

Spudguns can be very dangerous if built or used improperly. However, if they are respected, they can be great fun.

==Launcher safety==
*As a very basic summary- DON'T BE AN IDIOT WITH THESE THINGS!!!!!
*Use good, safe [[cannon construction|construction methods]] and materials.
*Follow the rules of basic gun safety: never point the cannon at anything you don't want to destroy, and treat it as if it's loaded at all times. Never look down the barrel.
*Always make sure you are firing in a safe direction that is free of people, pets, livestock, cars, houses and other property. Use a solid backstop or make sure you have a clear landing area.
*Don't look into the chamber of a [[combustion cannon]] that has failed to fire. Fresh air can make a rich gas mixture lean enough to ignite.
*Don't use PVC cannons in cold weather. Sub-freezing temperatures makes PVC brittle and increases the chances of catastrophic failure.
*Don't use a cannon that is cracked or heavily scratched, or has been dropped on a hard surface. Joints may be weakened and the pressure ratings on damaged parts cannot be trusted.
*Don't use excessive pressure in a [[pneumatic cannon]]. [[PVC]] pipe is not rated for pressurized air because of the shrapnel risk, so use in a pneumatic gun is considered to be outside pipe specifications in the first place. Never exceed the pressure rating of the lowest rated part.
*Don't use overly powerful fuels in a [[combustion cannon]]. Solid fuels and very reactive gases such as [[hydrogen]] or [[acetylene]] are not suitable for use in spudguns. Don't use oxygen to enrich the mix in a PVC cannon.
*Use hearing protection when firing loud combustion and hybrid cannons, especially in an enclosed space. Use eye protection if there is a chance of splinters or other debris from the projectile hitting the target.

==Don't shoot living things==
A typical spudgun is capable of launching a potato weighing 50-150 grams a couple hundred yards with the muzzle energy of a powerful handgun. Longer distances are easily achieved with rocks, PVC darts, golf balls, and other aerodynamic projectiles.

This energy, even when carried by a projectile as fragile as the humble tuber, is easily capable of killing someone, or at least breaking bones or putting out eyes. As to property damage, most launchers can put a vegetable through a piece of 1/2" plywood, and many can put it through 3/4" - which is very significant considering the construction of most residential buildings.

The same applies to short/and or small-bore launchers too.

Despite their great potential to do harm, it is not looked upon well if you (attempt) to use your launcher as a hunting instrument. They are often hard to aim, leading to a low probability of a clean (humane) kill - plus; it is illegal to do so.

Some people don't take the extreme danger of a projectile fired from a potato cannon seriously enough. There are frequent news articles about people injured by potato guns firing projectiles other than vegetables, or people being accidentally shot while handling the gun.

Accidental discharges are the most likely cause of injury however some individuals lack the mental capacity to keep their guns pointed away from others at all times. When a potato gun is pointed at a human being the dangers are extreme. Do not under any circumstances let the barrel of a potato gun point towards another human, even if the gun is not loaded.

The bottom line is: don't aim a spudgun at anyone, at any time, even if you think it's not loaded.

==Ammo Safety==
Some advise against shooting bolts, coke cans full of concrete, and other hard objects out of your gun; saying things along the lines of:
"Anything that is much harder than a spud can cause grievous bodily harm if shot at another person, or any animal for that matter."
...in actuality, even a tater will cause "grievous bodily harm" if shot at another living being. The danger lies in an increased chance of ricochet when using sturdy ammo - use common sense, and don't fire non-shattering ammo at close targets.

Some caution should be taken with shooting loose sub-munitions, specifically gravel or stones, with a [[sabot]] behind them - there is a significant probability of them jamming up, and the barrel being overstressed when the sabot tries to keep moving through the blockage, leading to a failure. Always wrap your lose projectiles in something - paper towels, old socks, and plastic bags are all acceptable.

Shooting water or other heavy objects from a cannon can overstress barrel fittings from the excessive recoil created. A sound grip must also be used when holding such a cannon as it can easily be blown out of one's hands.

[[category:Concepts]]

Primer

2007-04-15T12:20:24Z

Boilingleadbath: categorized

A primer is a chemical substance used to prepare an object for painting or gluing. However, to potato-gun enthusiasts, primer is generally used in the process of combining PVC/CPVC fittings and pipes by preparing them for the gluing process.

== How to use Primer ==

Primer is to be applied liberally to all PVC/CPVC joints, pipes or fittings (by use of a brush) where they are going to be connected together. In many cases, a brush is supplied with the primer. Application of primer should be done immedatly before the application of PVC cement. As always, the directions on the can provide the best advice on the process of [[solvent welding]].

== Health and Safety ==

Primer is a mixture of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, and acetone. Tetrahydrofuran is a known carcinogen in animals, so primer should be used in a well ventilated area. Gloves can be worn, but care should be taken to avoid spilling primer on them, as acetone penetrates through latex and rubber gloves, where it is absorbed through the skin. In addition, long term exposure of skin to these low-polarity solvents will severely dry your skin out, possibly leading to dermatitis. Swallowing primer may result in death, and chronic inhalation of primer fumes can cause damage to several vital organs including the central nervous system, liver, and kidneys. Symptoms of acute (short term) overexposure include dizziness, headache, nausea, confusion, vomiting, and unconciousness.

Be sure to read warnings and instructions.

== Types of Primer==

There are two basic "types" of building primer commonly used with potato cannons: clear and purple primer(s). The difference is simply that purple primer has a dye added to aid in the enforcement of building codes. This dye is essentially impossible to remove, as it soaks into the pipe fairly deeply.

Both of these are manufactured by many various companies and can usually be found at your local hardware store. Purple primer is easier to see when applied, clear primer can often be hard to detect after in dries. However, purple primer often leads to messy and unsightly purple smears on and around the project you are working on, best prevented by a generous application of masking tape around the non-joint area prior to gluing. Both are equally effective at getting the job done; it is up to you to decide which to use.

==Use as a Dye/Paint==

The unsightly stains caused by purple colored primer can be made to look less noticeable by covering the rest of the PVC pipe/fitting with primer also. Multiple coats may be necessary to achieve the desired shade. This dyeing method is especially resistant to scratching and was used in this .25 caliber piston valve cannon made by BillyBobJoe of the [[Spudtech]] forum.

[[Image:Primercannon.jpg]]

It should be noted that this rifle suffered a fracture in the rear female adapter, which was most likely caused by an overtightened SCH. 80 plug. The primer only penetrates the surface of the pipe/fitting and once it has had time to dry and dissipate, overall strength of the finished product should not be compromised.

== External links ==

Wikipedia article on primer: [http://en.wikipedia.org/wiki/Primer_%28paint%29]

[[category:Construction materials]]

Pressure regulator

2007-04-15T12:19:09Z

Boilingleadbath: categorized

[[Image:Pressure-regulator.jpg|thumb|right|300px|A high-pressure bulk tank regulator]]A pressure regulator is used to lower and stabilize the pressure from a gas or air source. The output pressure of most regulators is adjustable within a certain range, at the most up to the input pressure. There are several kinds of regulators made for different pressure ranges and gases, the most useful ones in spudgun application are:

*[[Paintball regulator]]s
*[[Propane regulator]]s
*[[Compressed air regulator]]s
*Various [[bulk tank regulator]]s

Regulators are most commonly used for providing a safe pressure from high pressure sources for [[pneumatic cannon]]s, and to provide a [[fuel meter]] with a constant pressure from [[propane]] tanks. It is important that the regulator is made to handle the input pressure, as well as any special conditions (freezing form liquid gas, flammable/corrosive gasses etc).

[[category:Accessories]]
[[category:Components]]