[Benjamin]

Hello.

A friend of mine is interested in EE, and has been using me for a sounding board on the topic of building a coil gun ('gauss gun').

Does anyone here have any experience on the subject?

His best guess, at this point, is to use replacement coils for an electric nail gun, possibly arranged in the same manner as a particle accellerator.

Appreciate any input.

-Ben

[cordex]

Did the exact same thing when I was in middle school. Had to explain to mom why the overhead light was broken in the living room.
Problem we had was triggering the coils and firing them in a useful sequence. Suggest using a fast responding LED based trigger now. I used to have some schematics around here somewhere ...

Check out American Science and Surplus for cheap capacitors.

I think it was George Hill who played with an arrow railgun, but that's a different concept.

[Penforhire]

Cordex, did you ever use the projectile itself to trigger coils (conductive section touching either bore/rail or brushes) as it travelled?

[cordex]

did you ever use the projectile itself to trigger coils (conductive section touching either bore/rail or brushes) as it travelled?
Nope.
If you try that, keep in mind that you'll need a momentary trigger - the projectile itself won't serve well as the final leg of a circuit. In other words, you want something that will allow the voltage to continue to pass, even after the projectile has gone beyond over the contact or your coil won't be exerting a ideal amount of force. Our electrical guru didn't think that design would work well, anyway. If you tried long strips of contacts rather than simple points, that might work. That way you could ensure voltage was cut off in time to keep the coil from pulling back on the projo.
Another problem with using the projectile as a physical portion of the switch is scalability. What works great for a low voltage, small gun can give some pretty nasty effects when you scale it up to a useful size. Trust me, the juice coming out of any serious caps will be plenty to weld the projectile to the contacts which could result in a nasty stuttering and self-destructive weapon.

[AJ Dual]

Perhaps an electric water gun instead.

Take a few of those big coffe-can sized capacitors, assuming you know what you're doing and won't get killed, machine a detonation chamber that's open at one end, and with about 1 oz of water at the bottom, jolt a couple of farads into the water.

BANG!

If you Google "Capacitor electric water gun" You'll get all sorts of interesting results.

[gun-fucious]

lots of fun stuff here too;
http://www.goldmine-elec.com/

[sch40]

A Russian engineer cooked this up not too long ago: *his site* (http://members.optushome.com.au/dbsite1/www.pskovinfo.ru/coilgun/index.htm)
--IIRC, the projectiles he uses have the same mass as a .22LR bullet, and about one tenth the velocity! Unfortunately, the recharge time is about 30 seconds.

Here are a few other pages devoted to coil-/rail-guns:
Coilgun Systems (http://www.coilgun.eclipse.co.uk/index.html)
Barry's Coilgun Designs (http://www.oz.net/~coilgun/home.htm)
Railgun 'Blog (http://www.rollette.com/railgun/)

Here's one on basic theory:
Basics (http://www.scitoys.com/scitoys/scitoys/magnets/gauss.html)

Good luck and have fun!
-sch40