Search found 3189 matches

by jimmy101
Fri Jul 29, 2022 6:11 pm
Forum: Combustion Cannons
Topic: How do you get consistent performance out of a "cheap" cannon?
Replies: 13
Views: 967

Re: How do you get consistent performance out of a "cheap" cannon?

what you are describing makes no sense at all. Simply squirting in from a torch with a mixing head is a terrible way to fuel. Makes zero sense.
by jimmy101
Thu Jul 28, 2022 10:29 pm
Forum: Combustion Cannons
Topic: How do you get consistent performance out of a "cheap" cannon?
Replies: 13
Views: 967

Re: How do you get consistent performance out of a "cheap" cannon?

It's simple. You use a propane Torch to ignite ? Use it for fueling ! Propane torches make the perfect mix by using the Venturi effect. The Problem is: A Venturi mix has to flow without resistance, so it can't be used with a loaded barrel....normally. But if I use a "over pressure" valve (we use ch...
by jimmy101
Mon Jun 13, 2022 3:06 pm
Forum: Combustion Cannons
Topic: Spud gun disguised as classic artillery
Replies: 6
Views: 1081

Re: Spud gun disguised as classic artillery

Gaseous fuels are usually pretty picky on the ratio being correct. For propane the combustion limits is about 3% to about 8% propane to air by volume. Outside that range the fuel-air wont ignite regardless of your ignition source. A meter pipe is perhaps the most elegant approach but overly complica...
by jimmy101
Thu May 19, 2022 11:23 pm
Forum: Ammo & Parts
Topic: Teflon lined barrel
Replies: 1
Views: 582

Re: Teflon lined barrel

Lower barrel friction might actually lower cannon performance. For combustion cannons the friction (especially the static friction) contributes a lot to performance by holding the ammo in position long enough for combustion to proceed and pressure to build. Combustion is actually a pretty close proc...
by jimmy101
Thu Nov 25, 2021 2:25 pm
Forum: Ammo & Parts
Topic: Does Ice Bullets Actually Work?
Replies: 7
Views: 2511

Re: Does Ice Bullets Actually Work?

I tip my hat to the Mythbusters, but I have to say I believe it is entirely possible. The Mythbuster ice bullet was brittle because they did not deaerate the water. A very cold, deaerated bullet would be hard, and not melt when fired. Speaking as a formulation chemist, Any problems with the ice bul...
by jimmy101
Mon Nov 01, 2021 10:47 pm
Forum: Ammo & Parts
Topic: Does Ice Bullets Actually Work?
Replies: 7
Views: 2511

Re: Does Ice Bullets Actually Work?

way back when people were using pykrete. Sawdust and water frozen. The sawdust makes the ice melt a lot slower.
spud_wiki/index.php?title=Pycrete
It should be mentioned int eh forum someplace as well.
by jimmy101
Fri Oct 22, 2021 7:43 pm
Forum: Pneumatic Cannons
Topic: How far does it go!
Replies: 7
Views: 2365

Re: How far does it go!

With four valve in parallel, I wonder if the opening of one inhibits the opening of the others? Do all four valves actually open together or do they inhibit each other?
by jimmy101
Thu Feb 25, 2021 12:28 am
Forum: SpudFiles Discussion
Topic: Adding Multiple Sparks In Combustion Chamber
Replies: 4
Views: 3102

Re: Adding Multiple Sparks In Combustion Chamber

What Jack said.

Plus, more than one spark increases the spark gap, that means the gaps need to be smaller if you are going to use the BBQ piezo.

BTW, multiple sparks must be wired in series, not in parallel.
http://www.advancedspuds.com/multiple.htm
by jimmy101
Fri Feb 19, 2021 4:35 pm
Forum: Hybrid Cannons
Topic: Need help
Replies: 15
Views: 7413

Re: Need help

hectmarr wrote:
Fri Feb 12, 2021 6:45 pm
Look at this, it can illustrate for you how to work with rupture disc.
LOL, looks like the fittings salesman's wet dream.
by jimmy101
Fri Feb 12, 2021 5:10 pm
Forum: Hybrid Cannons
Topic: Need help
Replies: 15
Views: 7413

Re: Need help

"best ratio" is not a well defined concept. Do you mean "most efficient" at extracting the energy in the explosion, or "fastest projectile" but that requires knowledge of projectile and barrel ... Long story short for 1X mixtures CB ratios between 0.6 and 1.2 are all about the same. Let other factor...
by jimmy101
Wed Feb 10, 2021 11:32 pm
Forum: Hybrid Cannons
Topic: Breech System For historical Pak 36
Replies: 26
Views: 9010

Re: Breech System For historical Pak 36

Looks like you will have to use more than 1x mixture, otherwise your chamber to barrel ratio will be too small. Do you know what your designs' chamber and barrels volumes are?
by jimmy101
Wed Feb 10, 2021 11:23 pm
Forum: Hybrid Cannons
Topic: Need help
Replies: 15
Views: 7413

Re: Need help

Will the fueling method of syringe work for up to 6x or maybe 8x? The biggest syringe that is easy to get is 70ml. If you fuel into a vented chamber you are probably limited to putting in no more than about 20% of the chamber volume. After that you'll be losing an unknown amount of fuel as it leaks...
by jimmy101
Wed Jul 15, 2020 6:40 pm
Forum: Pneumatic Cannons
Topic: Calculations related to pneumatic cannon.
Replies: 9
Views: 8370

Re: Calculations related to pneumatic cannon.

The ideal gas law is not usable in the situation of a pneumatic spud gun. Three state variables (pressure, volume and temperature)n al change. You need to do more complex stuff, like take in to account the heat capacity of the air. There are very nice tools for both pneumatics and combustion guns de...
by jimmy101
Mon Jun 15, 2020 4:58 pm
Forum: Combustion Cannons
Topic: I was hoping for some feedback on my oxy-propane combustion cannon.
Replies: 7
Views: 5122

Re: I was hoping for some feedback on my oxy-propane combustion cannon.

The biggest I usually see is 150 ml. That's big enough for 1x in a 3.75 liter (229 in^3) chamber, which is a pretty big chamber. https://www.amazon.com/Syringes-Scientific-Measuring-Watering-Refilling/dp/B07C71C1LH/ref=sxin_7_ac_d_rm?ac_md=2-2-bGFyZ2Ugc3lyaW5nZQ%3D%3D-ac_d_rm&cv_ct_cx=syringe&dchild...
by jimmy101
Mon Jun 15, 2020 4:53 pm
Forum: Hybrid Cannons
Topic: I bring you some cannon performance data
Replies: 5
Views: 4461

Re: I bring you some cannon performance data

Moonbogg wrote:
Sat Jun 06, 2020 2:07 pm
jackssmirkingrevenge wrote:
Sat Jun 06, 2020 6:05 am
jimmy101 wrote:
Thu Jun 04, 2020 10:31 pm
Caliper in the fruit isle? Just take a little length of barrel!
"Security? Yeah it's that weirdo putting limes through a pipe again..."

Yeah, that wouldn't look good.
Meh. Put a cut in the 1/2" long piece of pipe and wear it into the store as an ear ring.