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Problems with shoulder fired canon.

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Problems with shoulder fired canon.

Unread postAuthor: Tom » Sun Mar 30, 2008 3:59 am

Just like spuddin, I'm building shoulder fired rocket launcher. I don't have a chamber, the barrel(and chamber) is 75MM or 5.5 inch. I am going for the design and not really for the performance. So i purchased the PVC pipe yesterday and done some little testing, i tried to shoot a soda can. My fuel was lighter refill gas and i didn't measured it out. I tried to shoot but every time the projectile(soda can) gets sucked back into the barrel :?: . What could this be, maybe too much fuel?
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Unread postAuthor: BigGrib » Sun Mar 30, 2008 5:04 am

umm maybe too little fuel and the fuel burns out before the soda can exits the barrel and the vacuum draws it back into the barrel
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Yea, that's definitely going to get you at least a tazer.

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Unread postAuthor: Tom » Sun Mar 30, 2008 8:11 am

Thanks, i think it the second problem. I'm going to test it by measuring my amounts of fuel that I'm putting in.
But if it is that the fuel burns out too fast can i help it with drilling some holes in the pipe at a distance were it doesn't loose power? For the fuel-problem, i think I'm going to use a modified lighter.
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Unread postAuthor: DYI » Sun Mar 30, 2008 8:24 am

So how big is the chamber? Do you mean it is 75mm (3") of 140mm (5.5") pipe?

Here's your problem: The barrel is so large that, by the time the projectile reaches the end, the system's pressure is actually below atmospheric, and the ambient pressure pushes it back into the barrel.
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Unread postAuthor: Tom » Sun Mar 30, 2008 9:31 am

DYI wrote:So how big is the chamber? Do you mean it is 75mm (3") of 140mm (5.5") pipe?

No it's t 5 inch (1 meter) long by 75mm (3 inch) in OD :D .
I have tested the gun again but he doesn't shoot reliable, because of less or too many fuel. I think I should make a fuel meter tomorrow, just from a syringe or a pump. Then I can concentrate on the vacuum problem.
Thanks for the help!
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Unread postAuthor: DYI » Sun Mar 30, 2008 3:51 pm

Something tells me that Tom is using a translator program :roll:

Your post still makes no sense. One metre is 39 inches, not 5 inches. So is it 75mm diameter and 1000mm long, or is it 75mm diameter and 127mm long?
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Unread postAuthor: Tom » Mon Mar 31, 2008 12:10 am

ARGH.....
ahem.
It's just like you said "75mm diameter and 1000mm long". My propane meter is finished, nut I need to go too school :D .
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Unread postAuthor: BigGrib » Mon Mar 31, 2008 3:22 am

I dont think it's a translator problem i think it's a fat finger problem. I can recognize the symptoms a mile away
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Yea, that's definitely going to get you at least a tazer.

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Unread postAuthor: Brian the brain » Mon Mar 31, 2008 3:34 am

Something tells me that Tom is using a translator program


Tom is Dutch.I recognise the typical Dutch grammar.
He says "he"where in English one would say "it"
75mm diamiter by 1 meter( 1000mm) is a normal size.

You did get pressure rated pipe I hope, Tom??

Gewone PVC buis klapt uit elkaar.Meerdere video's van gezien.
Niet de eerste keer, maar er komt een dag...
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

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Unread postAuthor: psycix » Mon Mar 31, 2008 4:49 am

Tom how far back is the projectile?
When the projectile is sucked back it means your barrel is WAY too long for your chamber.
Put the projectile more to the front.
This will make your chamber bigger.

Zet t projectiel ongeveer op de helft van de buis. Dan heb je een 1:1 ratio.
Ik hoop dat t werkt.
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Unread postAuthor: Brian the brain » Mon Mar 31, 2008 7:26 am

The Dutch are taking over this forum hahaha
We need to form a clan!

Probeer was psysix zegt.Lijkt mij de oplossing.
En kijk uit want combustion valt onder de wapenwet
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Gun Freak wrote:
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Unread postAuthor: Jared Haehnel » Mon Mar 31, 2008 7:35 am

Don't worry I've got my trusty spud gun right here..... :twisted:
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Unread postAuthor: Brian the brain » Mon Mar 31, 2008 7:53 am

It's on now!! muhahaha :D

The Dutch are back to reclaim New York!

And from there we might as well take the world :twisted: :D

I tried to shoot but every time the projectile(soda can) gets sucked back into the barrel


Okay...maybe some other day...
A man can dream can't he?
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: psycix » Mon Mar 31, 2008 8:09 am

Een combustion valt onder de wapenwet?
Dus pneumatics tellen zeker als luchtbuksen oid?

Nee hoor meneer de agent, dit is een 3 meter lange 50mm luchtbuks :roll:


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Unread postAuthor: Tom » Mon Mar 31, 2008 8:26 am

Thanks for the comments, I know my english is bad. But rather a good grammar then those stupid posts with alot of bad grammar. BTB I'm using pressure rated PVC pipe. I will dril a now hole for the projectile block to make the chamber bigger.
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