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A place to ask general spud cannon related questions.
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Unread postAuthor: Ragnarok » Fri Dec 28, 2007 8:52 pm

Hotwired wrote:The reality is that no hobby coilgun has been made that even gets on the same map as a pneumatic air cannon.

Not entirely true. By size, a coilgun can compete.
I reckon I could eke more out of a 6mm coilgun design than anyone could from a 6mm pneumatic with the same barrel length.

I've got a coilgun simulator (not unlike GGDT), that gives a peak force of 500 Newtons for an average coil on a diagonal half-bridge set up running off 1kV.
HEAL struggles to do much more than that (~680N) with a 20mm barrel and 300 psi!!!
500 Newtons in a 6mm barrel is equivalent to over 2500 psi of pressure. Even if you take the average force of 355 N, that's still an unbelievable amount for such a small calibre - over 1800 psi equivalent.

In low calibres, a well made coilgun could give any pneumatic, or even hybrid that doesn't use insane mixes a good run for it's money.
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Unread postAuthor: Hotwired » Sat Dec 29, 2007 12:44 pm

Ragnarok wrote:
Hotwired wrote:The reality is that no hobby coilgun has been made that even gets on the same map as a pneumatic air cannon.

Not entirely true. By size, a coilgun can compete.
We are talking about with a high power 1KV capacitor bank glued on?

Ragnarok wrote:I reckon I could eke more out of a 6mm coilgun design than anyone could from a 6mm pneumatic with the same barrel length.
I smell massive bias... and say unto you that I could eke vastly more power out of said coilguns energy storage volume using compressed gas. In 6mm of course.

Anyway I hope a coilgun design does get up off the sketchpad but considering the specs you're talking of it won't be cheap at all, which generally is what stops new projects. A SCR alone to handle that kind of power will be fairly costly.

Ps. Post a link to the coilgun simulator :)
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Unread postAuthor: Ragnarok » Sat Dec 29, 2007 2:50 pm

Hotwired wrote:We are talking about with a high power 1KV capacitor bank glued on?

We're looking at about 1kV, maybe a bit more. Coilgun capacitor banks don't need to be that large to still get very respectable power out of them.

I smell massive bias... and say unto you that I could eke vastly more power out of said coilguns energy storage volume using compressed gas. In 6mm of course.

In theory, yes, but you'd need a much longer barrel. For example, look at this:
http://www.anothercoilgunsite.com/nf-portable-news.htm
That particular "ACG 85P" design has a 10 round magazine, and it'll fire a 4.5J (3.3 ft-lb) shot every second, all in a not unreasonably sized pistol based design, and that's not even using a diagonal half bridge configuration, or a whole load of other things that can increase the efficiency.
That's a rate of fire and energy I would be very impressed with from a pneumatic. And to get the same consistency from a pneumatic of even twice the size. You'd need a regulator in there as well, or use a gas like propane to get that consistency. I know you can theoretically do that sort of thing but you'd need some serious machining.

Take a look at the 300P at the same time. 11 Joules - that is a very considerable amount from something that size.

Anyway I hope a coilgun design does get up off the sketchpad but considering the specs you're talking of it won't be cheap at all, which generally is what stops new projects. A SCR alone to handle that kind of power will be fairly costly.

I expect it'll take me a while to get round to a full blown design, but I'm looking at a more modest design first - still a respectable one though.

Ps. Post a link to the coilgun simulator :)

http://www.gausspistol.com/Simulator.html
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Unread postAuthor: rp181 » Sat Dec 29, 2007 3:06 pm

Anyone thought of induction heating to heat up the air? A ceramic chamber, the induction coil, the some metal around it. In the chamber would be a suspended metal block, that would heat up the air, or make steam. On youtube, theres a video of someone melting steel in one.
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Unread postAuthor: POLAND_SPUD » Sat Dec 29, 2007 3:31 pm

heating air doesn't improve the effeciency as much as using steam... steam seems more practical and affordable as an alternative source of power than plasma or coilguns...

induction heating is not really needed here... I think it could work with some kind of boiler and basically any source of heat.... I am going to try it today - well at least I am going to try to generate some pressure by boiling water...

100 posts :D
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