Conductive, springy metal

Hey everyone, I'm a first time poster here with very limited electronics knowledge. Long story short, I'm building a gatling-potato gun (I'll upload a few pics as things get built if you are all interested) and I'm using a tazer to fire off each barrel as the cylinder spins. I need a 1/2'' to 3/4'' by about 2'' strip of conductive metal to connect the tazer to each barrel. As each barrel spins past the metal strips, they need to rake across each barrel to maintain connection. Any ideas on which metal would work best?

Interesting project! My first guess would be beryllium copper, aka spring copper. However, Wikipedia mentions its anti-sparking qualities, so it might not work so well in your specific application after all.

I don't need it to spark, only transfer the current from the 'rakes' to steel plates on each barrel to carry the spark inside each chamber. Or am I misunderstanding the definition of anti-sparking?

I should add that I believe its non-sparking quality refers to mechanical sparks (think cigarette lighter flint). I would imagine it would have no problem conducting tazer magnitude current to create electric sparks.

Well, we apparently posted at exactly the same time! Anyway, you're right.

Thanks Bob! Where would I turn to find some? Radio Shack? Home Depot?

Ah, I was afraid that might be the next question. Actually, since you mention hitting steel plates, maybe just use spring steel instead. It's not like you need great conductivity considering the juice a tazer will put out. Beryllium copper is tough, but not as hard as steel. Spring steel would probably be easier to find, and I would guess a lot cheaper too. Maybe another poster can tell where you can purchase one or the other...

How about springs themselves? They would flex and then return to their original position. Another concern, though. They might have a tenancy to weld to the metal strip.

But springs are readily available at hardware stores, and perhaps even auto parts stores (though at the auto parts store you might need to know the application in order to find the right spring).

Then, how about this for a whacky idea. Spray a stream of water at the metal strips. The water would need some sort of impurity, such as salt, for it to conduct electricity. But, that might make it too corrosive. But, maybe that seeds other thoughts.

Damn you Steve! Why'd you have to suggest something cool like using water?? Now I've got the 'go big or go home' gears turning in my head. This could very quickly change from a small workshop project to an impressive feat of engineering.... Oh well. Back to the drawing board to redesign the electrical system on the gun. I'm thinking this might end up looking like one of those old water cooled anti-aircraft/material guns from WWII ships.

Guess I've been watching too much MythBusters!!

And, my head hasn't quit yet...it kept thinking, what about a column of ionized gas? But I dismissed it because it didn't see like it could carry enough current. Then it occurred to me, a spark is conveyed by ionized air. So, how about just letting it arc across. Just mount a pointed rod close to the metal strips, close enough to make it a tiny arc so it only depletes a small amount of the energy so there's enough spark left for it to do it's job inside the gun.

Perhaps you could use a titanium drill bit, or a tungsten carbide bit. One of them might be able to stand up to the arcing over time.

Or perhaps a motor that feeds the arc rod to the metal plates until the arc voltage drops to a certain level, with feedback so it keeps the stark gap fairly constant. That way, as the metal at the tip of the rod burns away, and the arc voltage rises, the motor would move the end of the rod closer until the arc voltage drops again (i.e. the arc voltage would indicate how close the rod tip was to the steel plates.

I imagine two rollers that would pinch feed the rod.

I was thinking something along the same lines Steve, though I'd like my girlfriend to shoot it and I'm not too sure how keen she'd be if she saw sparks actively jumping.

Ah, well then...that does limit your options

As cool as that sounds, I don't have the skills to do that. I'm a pretty good carpenter and have the brain of an engineer, but electrical engineering like that is way above my level.

Wow ! This question has evidently provided some much needed deep excitement to the usually rather staid old engineers that inhabit this site ! (No offence meant !)

Anyway, how about a staid old well-established electrical engineering device already designed to provide a great deal of excitement, like . . . a commutator ?

There you already have a high current capability moving connection. Rip the guts out of an appropriately sized electric motor, detach the windings, fit the gun barrels in their place. Make holes in the outer casing to load rounds and shoot through. Drive the shaft by a pulley or gear from another motor underneath.

Each barrel is connected to two opposing segments fed by a pair of brushes, and fires each time it comes in line. Now perhaps with a couple of built-in diodes, the reversed current at 180 degrees would serve the purpose of ejecting the spent casing and loading the next round.

You know what ? I think I've just described what would have happened Mr Gatling had been an electrical engineer.

you could try a ball catch, a sprung loaded ball bearing in a metal tube, then make your track out of pcb. some ball catches have adjustable spring load .

You could use something like this or maybe tear the spring plates out and mount them to your liking. http://parts.digikey.com/1/parts/1641202-conn-battery-2-pos-right-angle-009155002541006.html

Seastrom has berylium copper option on various spring clips http://www.seastrom-mfg.com/subcategories.aspx?pl=Spring+Clips

Or try an outift like this and ask for a sample. http://www.becumfg.com/Becu-Beryllium-Copper.html

This looks to be a limited use home project. So, contact wearout is not a big issue. I would use 6061-T6 aluminum. While aluminum will develop an insulating oxide layer this will punch through at Tazer voltages. Additionally, sliding contacts are self-cleaning.