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OK coil gun caps ?

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ZakWolf

Thu Feb 10 2011, 05:51AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608

Are these good capacitors for a a medium power coil gun, i was thinking about getting 3 for 546 j (182.25j each)

Also i was thinking about using 20awg wire, sound good?

this is my 85 joule coil gun that i built for fun while i wait for my new caps, I used radio shack 22 awg wire and it rain out at 3-1/2 layers

thanks

aarpcard

Thu Feb 10 2011, 05:55PM

Registered Member #2848 Joined: Tue May 04 2010, 05:19AM
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Posts: 44

The caps look good to me. Heck, now I'm thinking about picking up a couple of those. They look great for the price. Although you might want to wait for confirmation from another user on here before pulling the trigger (no pun intended) because while I'm decently knowledgeable about these things other people on here know a lot more than me.

As for the wire, 20awg gauge will be better than the 22 gauge as there will be less resistance in the same length of wire, but ideally you're going to want something even lower. I'm using 16 gauge wire, (was using 24 gauge before) and the increase in current/decrease in discharge time and as a result performance increase was HUGE! Much more than I expected.

Try and find thicker wire. (Even the 16 gauge that I'm using is a bit too thin. Ideally you want something even thicker.)

Saz43

Fri Feb 11 2011, 01:14AM

Registered Member #1525 Joined: Mon Jun 09 2008, 12:16AM
Location: America
Posts: 294

Those are excellent capacitors for a coilgun, and at a great price... Hmm maybe I should buy a few.

Great work on the 85J coilgun too, looks like you're getting really good output power.

ZakWolf

Fri Feb 11 2011, 01:22AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

thanks

there are more caps on there to, i think they are 400v 3900uf for 15$ but they are sold out. Dont go buying up all the others :)

So i think 3 will be plenty for an upgrade and where would i get some SCR's that can handle that power and dont break the bank.

off topic side note does the smile face button work for anyone it hasn't worked for me for a month now.

haxor5354

Sat Mar 26 2011, 02:26AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

I made a coil gun 3 years back when I just started messing around with electronics. It had a bunch of different caps in parallel they were all at 200v or higher with 9420uf total so 185 joules. it only makes a small hole though an aluminum can. since that was back in the summer of 2008 (right after I graduated form elementry school), I barely knew anything about electronics not even Ohm's law!
my coil gun uses a mechanical switch instead of a SCR, and the coil very inefficient so I never made any coil guns ever since.
anyways, now I want to make a coil gun again just for the hell of it. big capacitors arent as expensive as I though they would be, a 350v 2500uf cap is only $15.
any advice on winding an efficient coil?
Img498gx3

Saz43

Sat Mar 26 2011, 03:53AM

Registered Member #1525 Joined: Mon Jun 09 2008, 12:16AM
Location: America
Posts: 294

haxor5354 wrote ...

... back in the summer of 2008 (right after I graduated form elementry school)..

Dang, that's impressive! When I graduated elementary school I was still on Legos.

haxor5354 wrote ...

any advice on winding an efficient coil?

Tight, parallel windings. None of that birds-nest jumble of wire coils like you see on youtube. Also minimize the airgap by making the coil inner diameter as close to the diameter of your projectile as possible. Use Barrys sim to get a pulse width less than 7 or 8ms but with a high peak current.

ZakWolf

Sat Mar 26 2011, 06:06AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

just like Saz43 said tight, and parallel windings. When i wind mine i sand a thin layer off the barrel to obtain a very smoother layer (unneeded) then i use one of these (i don't know what they are called)

to make two 1/4inch this plexi glass washers (you can also use iron washers). i do some measurements, supper glue them in place, then i wrap about ~3-4 inches of excess around the tube. (refer to picture) I am winding the power supply for the coil gun but it shows the same concept, use the excess wire to hold the wire in place then you have a nice tight wire you can wind to make a good coil. As far as calculations go i just wind a little, figure its enough and test it. My 356j coil gun shoots an 11gram projectile through 6 soda cans with nothing holding them down, there just set on my work bench and i shoot through them :).

haxor5354

Sat Mar 26 2011, 02:19PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

how many turns do you generally need?

ZakWolf

Sat Mar 26 2011, 05:17PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

there is no general amount, it depends on your wire gage and power. Before i improved my 85 joule coil i was using the thin gage wire from radio shack thats green i think its #26, anyways i had a ton of turns /layers, but when i fired it it didn't even puncture a soda can point blank. So i wound a new coil with a a little less then 40ft of 22 gage wire from radio shack. I only got about three layers on before the wire ran out but it can still shoot through an unmounted soda can four feet away :)

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