Science Fair

[pizlo]

Thanks for the replyes, I did angles last year, and it was a son of bitch finding and measuring the potatoes,(it was but 30 degrees fareieght) but I think a crono would be a good idea, I have my plans for a piston gun, and as a fall back I'll have a workng valve on my current pnue. New All I have to do is sweet talk of bribe the tech teachers. (too bad they're both men )

[paaiyan]

If you want consistent shots, I suggest switching to molded wax slugs. You can cast them in a piece of scrap PVC and they should come out the same every time.

[pizlo]

I've tried that before without success, how do I get them not to stick?

[jimmy101]

You can get more accurate results with spuds if you measure the weight of each spud. Combine the muzzle velocity (from a chronometer) with the mass to get the kinetic energy. This'll remove a lot of the shot-to-short variability you get with spuds.

To measure the mass of your spuds; (1) weigh the spud, (2) shove into barrel and collect the shavings, (3) weigh the shavings, (4) subtract (3) from (1).

Or, do like paaiyan said and make your own ammo. Besides wax, gasketed wood dowels also work. So do "store bought" ammo like tennis balls or golfballs.

[pizlo]

one other thing is I don't know If we could run a cord outside, so I might had=ve to build a big assed backstop.

[paaiyan]

Well first there's the obvious...

No-stick spray. as long as that spud isn't terribly tight, you should be able to get some kind of spray on it to get it to slide easier.

The backstop's easy. Just get some heavy foam, plywood, and visquine. you can figure it out from there.

[pizlo]

UPDATE: after talking to my tech teacher a bit, he gave me the tentative OK. I might be able to shoot stuff like wax out of my larger barrels, but I think the teachers would prefer nerf darts. I think now that I will test the FPS at different pressures. the schools compressor can go anywhere from 10 to somewhere above 100 and can be set to any psi.

[OuchProgramme]

Well first there's the obvious...

No-stick spray. as long as that spud isn't terribly tight, you should be able to get some kind of spray on it to get it to slide easier.

Yep, you can just get some of the no-stick pan spray-the ones you spray onto your baking pan-. They work realllyyy well.

[pizlo]

I think I might try that tomorrow.