Search found 27 matches

by spot
Wed Feb 10, 2010 12:36 am
Forum: Pneumatic Cannons
Topic: Which of these three designs would produce best performance?
Replies: 6
Views: 584

Option 2 would be your best choice, Option 3 isn't going to work (Piston is going to get pushed into your barrel), and option 1 is choking flow from the chamber.
by spot
Mon Sep 21, 2009 11:53 am
Forum: General How-To & Discussion
Topic: New Blow Forward System?
Replies: 10
Views: 1867

http://www.zdspb.com/media/tech/animati ... 3_7fps.gif

That would work... actually it does ^^

With some calculation of the seat diameter ofcourse, so that your valve only fires after enough air went to the loading mechanism.
by spot
Tue Jul 28, 2009 6:11 pm
Forum: Pneumatic Cannons
Topic: Piston Valves Explained Visually
Replies: 176
Views: 131848

Your pilot volume is huge... That's probably your problem.
by spot
Thu Jul 16, 2009 5:35 am
Forum: Pneumatic Cannons
Topic: Will a pneumatic cylinder keep up?
Replies: 6
Views: 561

What's wrong with a closed bolt system? That way you won't waste any gas actuating your cilinder ;).
by spot
Thu Jul 02, 2009 4:19 am
Forum: Pneumatic Cannons
Topic: Valve type...Piston, Shuttle or QEV?
Replies: 12
Views: 962

I think there's not much pilot volume at all, and he uses the spring loaded ballvalve to dump it as fast as possible. If I recall correctly, his valve didn't actuate very fast when he was using a smaller pilot valve. He needs that much pilot volume for it to not constrict flow.
by spot
Wed Jul 01, 2009 4:41 pm
Forum: Pneumatic Cannons
Topic: A way to fill it with a single stroke of a hand pump?
Replies: 3
Views: 358

I'll try to calculate it too :) I'm not used to using inches though... So I could be wrong :D Volume of the chamber of the gun: 1/4" x 1/4" x PI = 0.19634375 square inches 0.19634375 x 6" = 1.1780625 cubic inches Piston diameter? Compression ratio of 20:1 (like you calculated) => volume cilinder mus...
by spot
Wed Jun 10, 2009 5:43 am
Forum: General How-To & Discussion
Topic: Self-closing piston valve (brass fittings)
Replies: 66
Views: 26782

They don't seal 100 % :)
by spot
Tue Jun 09, 2009 2:00 pm
Forum: General How-To & Discussion
Topic: Carbon fiber tubing
Replies: 6
Views: 496

I don't think this would make it to spudding... Pure carbon tubes are very sensitive, when you smack it you will make a dent in it and the fibres will then continue to rip. That's why most of the time they wrap the fibers around an aluminum core. How are you going to connect this tube to other tubes...
by spot
Sat Jun 06, 2009 1:44 pm
Forum: Pneumatic Cannons
Topic: Piston and boltaction diagram
Replies: 29
Views: 2202

Just look at a real bolt-action gun. Support the barrel along the whole length of the stock. Your barrel will be out of copper / another metal so it will not wobble if the end isn't supported...
by spot
Sat Jun 06, 2009 6:57 am
Forum: Pneumatic Cannons
Topic: full auto questions
Replies: 6
Views: 451

To Thunderlord: I already suggested to make the bolt longer, so that it doesn't leak in the magazine. And the bolt HAS to seal, otherwise the chamber will keep leaking through the bolt. But, as I said it has to seal in front of the port, so that the air that remains in the pop-off tube can leak thro...
by spot
Fri Jun 05, 2009 4:41 pm
Forum: Pneumatic Cannons
Topic: full auto questions
Replies: 6
Views: 451

I think this design has a reasonable chance of working (It's always hard to predict :S). You will want to make sure though that the bolt is a little bit longer, so that the magazine is shut off when air can pass through. also make sure the bolt seals in front of the port, so that air trapped in the ...
by spot
Fri Jun 05, 2009 4:02 pm
Forum: Pneumatic Cannons
Topic: Piston and boltaction diagram
Replies: 29
Views: 2202

Let me get something clear: Are you going to pull the bolt backwards, or push the barrel forwards? IMHO in any case, the barrel should be supported by the stock (Or slide mechanism if you push the barrel forward, but if you are a accuracy nazi, that will cost you a little accuracy. But it won't be n...
by spot
Fri Jun 05, 2009 9:39 am
Forum: Pneumatic Cannons
Topic: Piston and boltaction diagram
Replies: 29
Views: 2202

The accuracy won't depend on how long the bolt slides over the barrel. (Unless you aim using the bolt, but that would be weird). Accuracy is more affected by the fit of the projectile, length of the barrel (So you can sight it better) and straightness of the barrel. It doesn't really matter much how...
by spot
Thu Jun 04, 2009 11:30 am
Forum: General How-To & Discussion
Topic: Im tearing my hair out with this calculation!!!
Replies: 18
Views: 793

What I would then do (And I'm by no means qualified, haven't even finished high school) is calculate the moles of gas in the chamber. Then subtract the moles of gad that needs to stay in the chamber (so if you want to regulate 50 psi, 50 psi should stay in the chamber). Next you calculate the moles ...
by spot
Wed Jun 03, 2009 10:31 am
Forum: General How-To & Discussion
Topic: Im tearing my hair out with this calculation!!!
Replies: 18
Views: 793

Dave_424 Gippeto tested the iron fitting s using his dead weight tester. While he didn't test a bell reducer, I think you would be safe, considering the other fittings withstood more than 8000 PSI (although you would need a safety margin of say 3, the fittings withstood nearly 4 (!) times your press...