Problems With Micro Railgun / Electromagnetic Projectile Accelerators / Forums

Forums

4hv.org :: Forums :: Electromagnetic Projectile Accelerators

« Previous topic | Next topic »

Problems With Micro Railgun

1 2 next

Move Thread

LAN_403

Microfarad

Mon Jan 16 2012, 01:55AM

Registered Member #4343 Joined: Mon Jan 16 2012, 01:45AM
Location: Florida
Posts: 10

Hello,
I am new to the forum, and I have a question about my micro railgun project. I have 7 photoflash capacitors connected in parallel, with a charging circuit. The rails are two 1/16" by 1/2" by 3" aluminum strips. They are mounted on acrylic plastic 1/16" apart. The rails are connected to the ends of the flash tube, which is itself connected to the charger. I know this set-up should work, as this is where I attached the coil in my 2880Âµf coilgun. However, when i try to fire the railgun, there is a massive spark, a very loud bang, and the aluminum foil projectile does not move. Any ideas on what I might be doing wrong?

Thanks in advance

m4ge123

Mon Jan 16 2012, 03:44AM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

I don't think your cap bank will work for a railgun. It's only capable of a few kiloamps and probably has enough ESL that everything gets welded together before the projectile gains any speed.

Turkey9

Mon Jan 16 2012, 04:02AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

With coilguns that small, you'll need to use an injector. Just connect the caps directly to the rails and shoot the projectile into the rails using a rubber band set tup or something similar. This will keep the projectile from welding, but only if the railgun is perfectly adjusted. You'll just have to play around.

Microfarad

Mon Jan 16 2012, 04:54PM

Registered Member #4343 Joined: Mon Jan 16 2012, 01:45AM
Location: Florida
Posts: 10

Thanks Turkey, I'll definitely try an injector. I have seen a few railguns this size that worked, but other people have had the same problem I am having, but never got any replies. I also may have been using to much aluminum foil. M4ge123, would having a good enough connection to prevent arcing stop it from welding together?
By the way, the entire railgun is in an Altoids tin.

Thanks again.

m4ge123

Mon Jan 16 2012, 09:12PM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

Once the projectile moves the connection will be interrupted and still weld everything together unless the projectile has sufficient speed (from an injector).
You probably shouldn't have it in an altoids tin because the steel could screw up the magnetic fields.

dingo27

Tue Jan 17 2012, 09:40PM

Registered Member #890 Joined: Tue Jul 10 2007, 10:06PM
Location: Slovakia
Posts: 180

Try some compressed air, there can be little air solenoids bought that are smaller than 9V battery, and for source of air you can use airsoft bombs (or the ones that are getting bubbles into soda)

Microfarad

Tue Jan 17 2012, 11:58PM

Registered Member #4343 Joined: Mon Jan 16 2012, 01:45AM
Location: Florida
Posts: 10

I'm not sure I am going to need an injector. I was doing a few more tests, and successfully fired a longer projectile...sort of anyway. It seemed to leave the rails prematurely, an have some vertical momentum. (The spark blew off the plastic on top of the rails, which I had forgotten to secure.) I tried it again without the plastic on top of the rails, and it went more forward. When I tried a roughly spherical projectile, it went almost straight up. Any ideas on what's going on here? Other similar railguns (like the micro railgun featured on hackaday and several like it on youtube) do not have an injector.

Turkey9

Wed Jan 18 2012, 02:09AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

It sounds like the projectiles are getting propelled by the spark and not the magnetic field, similar to an ETG. There are a couple threads on 4hv about them if you aren't familiar.

Microfarad

Wed Jan 18 2012, 03:14AM

Registered Member #4343 Joined: Mon Jan 16 2012, 01:45AM
Location: Florida
Posts: 10

Turkey9, that sounds like a likely explanation for the results I've been getting, however I am not at all familiar with ETGs. I tried Googling it, but none of the results were relevant. Could you point me to the threads you mentioned? (The forum search feature requires search terms with at least four letters.)
Also, I have a few questions about projectiles. Do they absolutely have to be nonferrous for the railgun to work? And would using a projectile made of a material with a lower melting point than that of the rails reduce rail erosion? If you have any ideas about how to prevent what Turkey9 said might be happening, I would greatly appreciate it.

Turkey9

Wed Jan 18 2012, 05:49AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Sure, here is the big thread I was thinking of:

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob