Search found 3197 matches

by jimmy101
Mon Feb 26, 2024 5:09 pm
Forum: Combustion Cannons
Topic: combustion spudguns
Replies: 9
Views: 1275

Re: combustion spudguns

Go for it.

But how will you measure the diesel?

The MOST critical thing is the correct amount of fuel. If you are off by 10% the gun won't ignite, let alone fire. The correct amount of fuel is much more important than what the fuel is.
by jimmy101
Mon Feb 26, 2024 5:07 pm
Forum: General How-To & Discussion
Topic: P.A.C. 6, Semi-Auto Air Cannon
Replies: 23
Views: 4816

Re: P.A.C. 6, Semi-Auto Air Cannon

What is it that you would like to know?
by jimmy101
Fri Feb 23, 2024 10:38 pm
Forum: Combustion Cannons
Topic: combustion spudguns
Replies: 9
Views: 1275

Re: combustion spudguns

It will most likely to decrease performance. Mostly because of how hard it would be to accurately measure. In general, hydrocarbon fuels have nearly identical energy contents per unit air. http://www.inpharmix.com/jps/Combustion_fuels.html The only outliers are Hydrogen (not a hydrocarbon) and acety...
by jimmy101
Thu Dec 07, 2023 12:35 am
Forum: Hybrid Cannons
Topic: Hybrid disk burst pressure effect on performance
Replies: 20
Views: 29899

Re: Hybrid disk burst pressure effect on performance

A mesh screen would kick up turbulence but also suck up a lot of heat. We have discussed before if running the chamber fan during firing might increase the burn speed. Way back when I measured burn speed in a closed chamber at 1x with/without the fan running and with one or three sparks gaps. There ...
by jimmy101
Tue May 16, 2023 12:16 am
Forum: General How-To & Discussion
Topic: how to convert fps into mph
Replies: 21
Views: 34423

Re: how to convert fps into mph

The point is to know how to solve problems (not just this problem) without resorting to magical numbers specific to only one problem, like 22/15. Dimensional analysis is based on the most fundamental mathematical fact: you can multiply anything by "1" without changing the underlying amount . If you ...
by jimmy101
Mon May 15, 2023 11:44 pm
Forum: Pneumatic Cannons
Topic: How much velocity do you need to comfortably reach 300 meters range with a cannon?
Replies: 4
Views: 3714

Re: How much velocity do you need to comfortably reach 300 meters range with a cannon?

300 meters is a long way. Remember that a pneumatic is probably going to be operating at less than 150 PSI, which is the max pressure of a typical shop compressor. Compare that to a typical 0.22 rifle that has an effective range of about 150 yards. That low power rifle operates at twenty thousand PS...
by jimmy101
Sun Dec 11, 2022 11:58 pm
Forum: Hybrid Cannons
Topic: How accurate is your hybrid gun?
Replies: 1
Views: 2482

Re: How accurate is your hybrid gun?

1. Yes, fueling with a syringe is reproducible. 2. Shot to shot variation should be less than 10% in muzzle velocity, if you are using consistent ammo. Spuds are generally not very consistent. :) 3. Depends on what you mean by "long range". For anything powered by gases with a smooth bore and non-ae...
by jimmy101
Wed Oct 19, 2022 5:45 pm
Forum: Pneumatic Cannons
Topic: Saftety of PVC Pipe
Replies: 14
Views: 11611

Re: Saftety of PVC Pipe

getgray wrote:
Wed Oct 12, 2022 11:09 am
Fun fact. PVC shrapnel does not show in an X-ray. That should answer the question if the data sheets from the manufacturers weren't enough.
yes it does
http://news.bbc.co.uk/2/hi/americas/6064692.stm
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: 8800

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: 8800

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: 7
Views: 7823

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: 3740

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: 16126

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: 16126

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: 5432

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?