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Short question topic

A place to ask general spud cannon related questions.
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Re: Short question topic

Unread postAuthor: wyz2285 » Tue Feb 11, 2014 5:39 am

So I managed to make a 3000 bb drum mag for my SCAR. Freaking awesome, but got one problem. To truly take advantage of my hi-cap/drum mags, I installed the angry gun rapid fire kit(part for the slightly increased rof mostly because it reduces the stress that I'm putting on the gun by firing a couple hundred rounds). So in full auto mod I wasn't able to have reliable reload action and after playing with the pressure I'm damn sure it's because the regulator wasn't capable of providing enough flow of air to work the bolt in full auto (semi is damn fine though, 305 fps for 5 shots straight, no variations 8) 1 fps variation in 10 shots with 148 psi, 0.35g bbs)
I bought the v2 inline regulator from custom products, making a standard duo reg setup instead of my current single regulator hopefully for better flow. So does anybody had similar problem? What do you use to supply your HPA airsoft gun?
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Re: Short question topic

Unread postAuthor: jrrdw » Tue Feb 11, 2014 7:56 am

I think you're running into a combination of small issues. BB consistency, porting (polishing, chamfering) any flow restrictions other than regulating (air passage sharp angles). This is just quick thinking of the obvious.
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Re: Short question topic

Unread postAuthor: wyz2285 » Tue Feb 11, 2014 9:45 am

But other GBB converted to HPA systems I saw on youtube doesn't seem to have the same problem, and all of them use a Palmer or custom products v2
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Re: Short question topic

Unread postAuthor: jrrdw » Tue Feb 11, 2014 10:12 am

wyz2285 wrote:But other GBB converted to HPA systems I saw on youtube doesn't seem to have the same problem, and all of them use a Palmer or custom products v2


Are they working with the same magazine capacity that you upgraded to?
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Re: Short question topic

Unread postAuthor: wyz2285 » Tue Feb 11, 2014 10:30 am

Obviously not, but shooting in full auto the rate of air consumption should be the same I think, shooting 200 rounds should consume the same volume of air per shot as 20.
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Re: Short question topic

Unread postAuthor: jrrdw » Tue Feb 11, 2014 10:54 am

It also could be the change in volume in the HPA tank even though the gauge numbers indacate a steady 148PSI. I can't help but think it has a effect on over all preformance.
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Re: Short question topic

Unread postAuthor: wyz2285 » Tue Feb 11, 2014 2:51 pm

We'll see once I get the new reg working
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Re: Short question topic

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Re: Short question topic

Unread postAuthor: Talk » Tue Mar 04, 2014 3:22 pm

Combustion cannon Question:

I have an idea to make a mini combustion cannon and I'm not sure which method to choose.

Method 1 : normal combustion cannon configuration ,fuel in, ignition ,projectile out.
untitled method 1-crop.JPG
untitled method 1-crop.JPG (23.5 KiB) Viewed 381 times


Method 2 : in method 2, there is a trigger system which holds back the ignited gas.
untitled mehod 2-crop.JPG
untitled mehod 2-crop.JPG (24.36 KiB) Viewed 381 times


This is how the trigger will work in method 2, pulling the trigger would raise the barrier allowing the gas to push the projectile out.

1)question : do you think the trigger mech will slow down the rate at which the projectile travels?
2)can a combustion cylinder of height :11 cm ,radius2: 2.5 fueled with enough butane can push out a .22 pellet with a decent force?
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Re: Short question topic

Unread postAuthor: cammyd32 » Tue Mar 04, 2014 7:17 pm

First things first method 2 would not work, the pressure generated by a combustion cannon is due to the sudden rise in temperature, after which the pressure drops rapidly, so it is impossible to 'contain' the pressures generated by a combustion, its like setting off an atom bomb in a box and expecting that when you open it you have an instant explosion, it's just troll science. So, method 1 it is.

As to your second question, it depends on your definition of 'decent force' Although I can expect your definition would be somewhere in the region of standard airgun power (around 10-11 ft lb)
Best thing to do would probably be to have a nice look at that lovely programme, HGDT , type in your parameters, and see what comes out :wink:
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Tue Mar 04, 2014 7:34 pm

What cammy said.

cammyd32 wrote:As to your second question, it depends on your definition of 'decent force'


Atmospheric pressure combustions are a bad idea for small calibres if you want something better than an airsoft gun. Go hybrid or go home :D
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Re: Short question topic

Unread postAuthor: Talk » Wed Mar 05, 2014 11:37 am

its like setting off an atom bomb in a box and expecting that when you open it you have an instant explosion, it's just troll science. So, method 1 it is.


I was thinking something like that would happen with method 2 since i have very less interest in combustion and hybrids, I still asked the question to be sure.
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Wed Mar 05, 2014 12:06 pm

Well, there is a way to use a combustion to store power, in the manner of the Sims-Dudley dynamite gun:

Image

It is a pneumatic cannon with a conventional chamber, valve and barrel - however instead of being fed by a compressor, it used a magic powder charge to push a piston down a tube, compressing air past a one-way valve on the other end.

Effectively, it is a single stroke compressor that uses the power of hot expanding gasses.

To give to an idea of what might be possible, imagine you have a piston in a 3" diameter and 15" long tube, connected via a one-way valve to a 1" diameter chamber 2" long. Given a big enough push, the piston could take your chamber to 1000 psi. As you could however have the air push the projectile directly, it seems like an extra complication to attach a separate chamber and valve, considering it's adding dead space and increasing stress on the system by having to retain compressed air.
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Re: Short question topic

Unread postAuthor: Talk » Wed Mar 05, 2014 3:51 pm

i could use the dynamite gun mechanism but i had plans to build a combustion gun as the size of a pistol so i asked about the 11 cm cylinder with 2.5 cm radius.
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Re: co2 bottle pin valve question.

Unread postAuthor: Alanstone » Fri Mar 21, 2014 11:31 am

Please excuse my ignorance with regard to this question. I bought myself a qb 79 and got 9oz CO2 bottles to power it. Its the first time that I actually had a co2 bottle in my hands. So to my question: could the pin valve on a co2 bottle not be used directly in a hammer valve with the hammer striking the pin valve?
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Re: Short question topic

Unread postAuthor: cammyd32 » Fri Mar 21, 2014 3:53 pm

Theoretically yes, but due to the inline nature of the valve you would need an additional component which would then direct the gas and allow the hammer to be external, and lets be fair, If you're going to the effort of making that component, you might as well buy up or make the actual valve too.
Also from what I recall those valves aren't exactly brilliant hammer valves. The valve stem and seals on CO2 bottles aren't built for that kind of abuse, you could find yourself with a potentially very dangerous valve failure if you went a bit too aggressive with your hammer.
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