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7.5 Cm Pak 40 Project - Airsoft cannon replica

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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7.5 Cm Pak 40 Project - Airsoft cannon replica

Unread postAuthor: battlelava » Tue Feb 21, 2012 10:42 pm

So after to many months of debating on what to build I've finally settled for this. The devastating Pak 40.
Image

So here's some specs for the build.
Over under design so I can incorporate the chamber into a recoil mechanism (I'll vent some of the hot gas's to force the gun to recoil)
A 52" x 1" barrel (have to keep it short to keep it transportable)
A 40" x 2" chamber (trying to keep the pressure low for safety)
A full mount
A recoil system (the forced recoil system I mentioned earlier)
A full operational elevation and traverse mechanism
A chicken Plate shield in front
Some sort of sights (not sure how to work them out yet possibly like the m203s leaf sights)
Shooting clumps of 50 .2 gram bbs is some type of container (still to be designed)
Ditched the burst disk idea I had to reduce even more pressure
Some HGDT results
Image
Still trying to reduce the fps a little to prevent injury to other players as of right now its got a muzzle velocity of 699 (approx)
What do you guys think, first major build should be started building it after I work everything out on paper (I can't afford to mess up)
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Re: 7.5 Cm Pak 40 Project - Airsoft cannon replica

Unread postAuthor: jackssmirkingrevenge » Wed Feb 22, 2012 12:45 am

battlelava wrote:The devastating Pak 40.


I've seen a couple of these in the flesh around the world, very impressive piece.

Over under design so I can incorporate the chamber into a recoil mechanism (I'll vent some of the hot gas's to force the gun to recoil)


I think you'll find that if the chamber is mounted free on a low friction rail it will already recoil a considerable amount without the need for assistance.

Ditched the burst disk idea I had to reduce even more pressure
Some HGDT results that can only be seen with a scanning electron microscope


crop por favor :)

What do you guys think, first major build should be started building it after I work everything out on paper (I can't afford to mess up)


With the dimensions you have in mind, I think you're chosen the wrong aesthetic model, there are more adequate German WW2 anti-tank weapons I can think of that suit the scale of your build better:

Image

Image

Image
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Unread postAuthor: battlelava » Wed Feb 22, 2012 7:55 am

Sorry about not cropping I can't believe I forgot to.
Is that a pak 36 I was thinking of it, or maybe sleeving the whole thing in a 3" pipe. To give it a better appearance
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Unread postAuthor: evanmcorleytv » Wed Feb 22, 2012 5:21 pm

Actually, The BEST Combination I've EVER gotten with a combustion was a 10 inch by 3 inch chamber, with a 2.5 foot by 3 inch chamber. That should help with power, range, and size.
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Unread postAuthor: battlelava » Wed Feb 22, 2012 5:26 pm

evanmcorleytv wrote:Actually, The BEST Combination I've EVER gotten with a combustion was a 10 inch by 3 inch chamber, with a 2.5 foot by 3 inch chamber. That should help with power, range, and size.
two chambers? I'm confused
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Unread postAuthor: blind909 » Wed Feb 22, 2012 10:32 pm

I think that what he meant was a 3 inch diameter, 10 inch long chamber, and a 2.5 foot long, 3 inch diameter barrel.
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Unread postAuthor: battlelava » Wed Feb 22, 2012 10:36 pm

blind909 wrote:I think that what he meant was a 3 inch diameter, 10 inch long chamber, and a 2.5 foot long, 3 inch diameter barrel.


That would make sense. According to HGDT it would reduce my output by half compared to the Barrel and Chamber I had planned.

Edit: Heres a picture of the HGDT results that you can actually see :)

Image

I'm not sure about the projectile friction and initial position part... Should be close though as i remember someone saying it was 2 psi resistance.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 22, 2012 11:58 pm

If you blow down the barrel and the projectile moves, then friction is less than 3 psi.

Initial position is basically "how far down the barrel is the projectile when loaded", in most sensical launchers this is zero.

Are you fitting a chamber fan? if not, put the diameter and flow to zero.

I say model it on a 37mm anti tank gun like the Panzerabwehrkanone 36 or this lovely Bofors:

Image

Another advantage of the Pak 36 is that you can "realistically" do this :D

Image
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Unread postAuthor: battlelava » Thu Feb 23, 2012 10:30 am

What about a pak36 with this for a breech without the "charge" at the end of the muzzle. I don't know how easy it would be to make an end attachment like that that's not deadly especially with my limited resources.
Image

This is were I got it from and it seems to work really good for him, And then with the recoil I can make it auto eject.
http://www.youtube.com/watch?v=odbIbTxocjM

edit: Fixing the picture I'm not sure why they keep coming out so massive.
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