1300 Foot Pounds large bore airgun

[billzweig]

This is a first test of the prototype, not quite an air-gun yet. In this design I am trying to obtain higher velocity by eliminating the complex air path found in most guns and by releasing the projectile only with the full air pressure behind it (in a regular design the projectile starts moving as the pressure builds up thus increasing the volume)
The design is using an high voltage discharge to trigger the process. In my experimental setup it is quite a big circuit, but can be significantly reduced in size. I will show more details soon.

youtu.be/3bh1qDong58

[Rob M]

nice.. I see a capacitor and some nicad batteries in there.  Im assuming its an electric dump valve of your own creation .. Is it a pilot system , is it venting gas to fire ?? cool either way and impressive with such a small volume of air

[rsterne]

Interesting concept.... How long is the barrel?.... I assume air, not Helium?....

Bob

[BackStop]

I this a PCP or is the pressure made by the "high voltage discharge"?   If the latter, then this is essentially a firearm, not an airgun.   Right?

[subscriber]

Nifty!

[billzweig]

nice.. I see a capacitor and some nicad batteries in there.  Im assuming its an electric dump valve of your own creation .. Is it a pilot system , is it venting gas to fire ?? cool either way and impressive with such a small volume of air

I am preparing a full description of the system. The electrical discharge (400V, 400uF) is triggered by 30KV spark gap.This is only one way to trigger and I do have two other options I shall describe.

[billzweig]

Interesting concept.... How long is the barrel?.... I assume air, not Helium?....

Bob

Yes, compressed air. The barrel is 32" long and is really the weakest part of the system. I've made it myself and I am not that happy with it.  I think I can get better results with a Lothar Walther barrel, but I did not manage to get one from them.

[billzweig]

Nifty!

Thanks

[billzweig]

I this a PCP or is the pressure made by the "high voltage discharge"?   If the latter, then this is essentially a firearm, not an airgun.   Right?

Not quite. The propellant is compressed air, not chemicals. The high voltage just triggers the release.

[rsterne]

You are achieving greater efficiency than I have ever seen.... The maximum possible FPE, which is based on the energy input, can be calculated as follows:

Bore area (sq.in) x pressure (psi) x barrel length (ft.)…. That is (0.45 x 0.45 x PI/4) x 4000 x (32 / 12) = 636 lbf. acting through 2.67 ft. = 1698 FPE....

That assumes a constant 4000 psi over the entire barrel length (which requires a reservoir of infinite volume)…. and that 1700 FPE includes the energy of the air being accelerated as well.... The mass of air in your barrel at 4000 psi is 25.2 grams (based on a density of 0.3024 g/cc at 20*C)…. That means the air weighs more than your bullet.... Logically, achieving 1300 FPE out of a possible 1700 would be pretty difficult under those circumstances.... Typically, a very good PCP does not achieve even 50% of the theoretical maximum, ie 850 FPE would be an excellent result....

I will be looking forward to seeing how your system works.... I suspect that your peak pressure may be well over 4000 psi because of the energy of the spark discharge raising the temperature.... the combined energy giving the boost you are seeing... Just my current thoughts.... I've been wrong before.... 

Bob

[T3PRanch]

Plasma discharge can go to 45000 degrees! Might be a small    pressure jump from that!

[darkcharisma]

i am watching with extreme interests.

[grand-galop]

Does anyone mentionned the volume of air the valve contained??  The video show  better working of any inline valve..   Thanks for sharing..

[Insanity]

Very interesting that is a lot of power being made. I am awaiting the description.

[TPL]

I remind you it takes energy to accelerate a projectile.

[Privateer]

Are you compressing ambient air or pure oxygen?
Pure oxygen is explosive.

[MJP]

Energy does not come from nothing, couple of Joules from the capacitor at best, spark in range of nano seconds does not heat the air so much.
Burst disk in very critical pressure and opening a piezo valve to let more air in could work, or using the arc to rupture the disk is another.
Interesting to see how this unfolds.

Marko

[billzweig]

I must apologize. There is an error in the results of the test. I've recovered one of the spent bullets and realized I was using lighter bullets for the test. I've machine those bullets in small batches of various sizes and the 23 grams was mixed with the 18.5 grams bullets. So the weight used in the video was 18.5 gram (293 grain). Consequently the energy is 1055 ft/lbf (1430 Joules).
Please forgive me. I was away from the shop for some time and eager to start the testing. And in some way fooled myself by the excitement. I will make anew video - including all the technical details - to replace the current one.

[Rob M]

thats still really impressive as texan users strive to fall 200 fpe lower than that.

[subscriber]

So the weight used in the video was 18.5 gram (293 grain). Consequently the energy is 1055 ft/lbf (1430 Joules).

850 FPE would be an excellent result....

So, still impressive, Bill.  Thanks for sharing your efforts.