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Working on a new Coilgun Carbine (600+J)

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LAN_403

Backyard Skunkworks

Tue Jun 09 2009, 07:13PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Now that I'm done with high school (as in done, on to being an EE major this fall!

) I have enough free time to work on a few cool projects, one of which is one of the more powerful handheld coilguns built so far. I have a ton of disposable camera flash capacitors I've accumulated over the last little while, so I should be able to pack a few hundred joules worth of energy at 300V into a small carbine body loosely "styled after" the SIG 552.

Here are the specs for the project as of now:
300V
500-800J electrical energy
Mechanical switching (upgrading to SCRs soon)
Diodes for reverse protection
Unknown mechanical energy to expect as of now... (Assuming around 15 (+/- 10) J)
8x50mm projectile
Portable!!!

I decided to do this project because I'd seen a lot of people make powerful coilguns, and a lot of people make portable coilguns, but I've seen very few people make powerful portable coilguns.

I'll use this thread to talk a bit about my construction and testing over the next little while, and eventually do a write up of it in the projects forum.

Here is a vid I made a few months ago using part of the cap bank and the same coil: (Please no comments on my taste in music!)

-Skunkworks

P.S. 400th post

big5824

Tue Jun 09 2009, 08:27PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

looking good :) Just get changed to SCRs asap, they are a huge performance increase normally. Also get some vids of it shooting cans etc :)

Backyard Skunkworks

Fri Jun 12 2009, 02:52PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Yesterday I put together the drum magazine style part of the cap bank out of two circular arrays of 19x 120uF disposable camera caps. These bad boys are a combined 205J (+/- 20%) @300V.

Bonehead

Fri Jun 12 2009, 03:08PM

Registered Member #2046 Joined: Sun Mar 22 2009, 01:12PM
Location: Stockholm, Sweden
Posts: 23

Those look pretty cool, how are they going to be attached to the carbine itself?

Backyard Skunkworks

Fri Jun 12 2009, 04:38PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Bonehead wrote ...

Those look pretty cool, how are they going to be attached to the carbine itself?

A connector with 10 gauge wire on either side. This way I can connect and disconnect the drum that sits under the carbine for more or less power.

aonomus

Sat Jun 13 2009, 02:07AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Out of curiosity, have you considered the potential inductance due to the + and gnd rails being coiled?

Looks cool, hopefully you can switch to SCRs and get a better way of switching.

Barry

Sat Jun 13 2009, 01:58PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Looks cool! I highly recommend soldering each connection to capacitor terminals. It will lower the resistance, avoid sparks and keep them from blowing off the copper wire when firing.

Cheers, Barry
I don't need to test my programs. I have an error-correcting memory and an error-correcting modem.

Killa-X

Sat Jun 13 2009, 03:59PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Hah, I did this for my disc launcher!! I had a ton of disposable camera caps, and i dumped most of them last year :( But, I still had a ton around :D Even some 330V 160uF ones :D

Sadly, The flaw is that my labels, are blocked. I know most are 120uF, and 2 are 160uF

Arcstarter

Sat Jun 13 2009, 07:04PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Looks nice :D. Solder those connections! If you are having a hard time just rough the joints up, then use flux and heat the about-to-be solder joint until the flux starts to run, then use a soldering iron and the solder. At least that is how i did it for those kind of joints and copper strapping.

If you are looking for some cheap SCR's you can try LittelFuse. They have some pretty good small SCR's. For you i would probably suggest S4065K, they are 950 amp pulse for either 10ms or 8.5ms, and 400 volts. they also have 600 and 800 and 1000. I have the 1000 volt type, SK065K, and they work great. 5 in parallel will switch a 1950uf 800vdc 624 joule capacitor bank into a dead short. Over, and over, and over again. Also Killa-X has a few of the 800 volt ones, and they work great for him. A single AAA is good enough for the trigger. They are around 5-6 bucks a piece at Newark, probably cheaper on LittelFuse.

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