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Ethliel

Wed Apr 21 2010, 04:59AM

Registered Member #2813 Joined: Wed Apr 21 2010, 02:52AM
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Posts: 3

I have recently built a "micro-railgun," based on the generic design found all over the internet, with two pieces of aluminum bar bolted between Plexiglas, powered by photo-flash capacitors.

While building it was relatively easy, I am having trouble with firing the device successfully. I read that the easiest to use armatures for such small railguns are simply wadded up pieces of aluminum foil. I am wondering if anyone out there knows the correct way to use the aluminum foil.
I started by just making a ball and stuffing it in, which resulted in the capacitors discharging though the projectile, with no sparks, plasma, arc-welding, or anything. I assumed this was because the projectile was to large, so I replaced it with one that was lighter and smaller. This one made sparks, and got stuck to the rails. After 13 tests, only two projectiles have moved, about 1 cm each. Any tips?

My capacitor bank is 330 V, 320 microFarads, and I have extra capacitors to get to about 1500 microFarads. Rails are about 1.5 mm apart, and 4 inches long.

Thanks for the help!

Tesla_trooper

Wed Apr 21 2010, 06:20PM

Registered Member #82 Joined: Thu Feb 09 2006, 12:03PM
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Posts: 3

Have you tried field augmentation by permanent magnets or an extra pair of rails/coils?

Andyman

Wed Apr 21 2010, 06:52PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Small railguns are most effective if you have some sort of injector to give the projectile some starting velocity. That way, it has less of a tendency to instantly weld to the rails and bind. Most people use a pneumatic system to do this.

Steve Conner

Thu Apr 22 2010, 11:01AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You need moar power!

GhostNull

Thu Apr 22 2010, 11:15AM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

YES, MOAR POWAR and also look through previous threads and read the 4hv wiki there should be more than enough info on this forum for you to answer your own questions

and Steve I don't think German articles are very helpful

Ethliel

Thu Apr 22 2010, 05:24PM

Registered Member #2813 Joined: Wed Apr 21 2010, 02:52AM
Location:
Posts: 3

Good news!

I doubled the size of my capacitor bank, stuck the projectile about 1 cm into the gun (so it did not need to move as far) and it fired wonderfully.
The current model is not large enough or well designed enough to allow adding an injection system, but I have already built an air tank/ injection system for the next railgun I build. The copper for the rails comes later this week, along with other rail enclosure parts.

I like the idea of augmentation with magnets, but I am unsure of how ecavly to do that, and my search for information has been unsuccessful. Could someone point me in the right direction?

Dr. Slack

Thu Apr 22 2010, 06:48PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Ghostnull wrote :

and Steve I don't think German articles are very helpful

The German article wrote:

Laut Datenblatt (Epcos) haben diese Kondensatoren eine Impedanz von 25mOhm und eine Eigen-induktivitÃ¤t von 25nH. Die Energie bei 350V Ladespannung betrÃ¤gt 4 kJ.

I think most of the 4kJ and 25mohm stuff is perfectly verstehen

Tesla_trooper

Thu Apr 22 2010, 07:53PM

Registered Member #82 Joined: Thu Feb 09 2006, 12:03PM
Location:
Posts: 3

Ethliel wrote ...

Could someone point me in the right direction?

Use the right hand rule for lorentz force and attach the magnets so their field points in the same direction.
Or just use two coils, one above and one underneath the rails.
here just use the picture entitled "seriell":

Or this one from the grandmaster of railguns:

GhostNull

Fri Apr 23 2010, 01:01AM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

===Theory===

Railgun Theory by Matthew E. Massey

howstuffworks.com - explanation with animations

iop.org - Theoretical limits on exit velocity

Jengel and Fatro's Rail Gun Page

===Amateur===

PowerLabs Rail Gun research

Railgun theory, design, construction, and testing

Railgun Blog by Jason Rollette

Miniature Experimental Railgun

Tim Ventura's 90's-era Railgun Designs

American Antigravity's Mass-Driver Demo + Video

+EML Laboratoryï¼ Japanese Experimentï¼‹Video

===University===

The University of Texas at Austin Rail Gun

Auburn University Rail Gun

===Military===

Electromagnetic Railgun: An Innovative Naval Program

hope that helps

and it's good to hear it works now but if you are making a bigger railgun you WILL NEED MOAR POWAR!!!!!!!!

Ethliel

Fri Apr 23 2010, 02:33AM

Registered Member #2813 Joined: Wed Apr 21 2010, 02:52AM
Location:
Posts: 3

Thanks for all the help! As this is quite a large school project, I've seen a lot of what's out there about railguns, but I never thought of looking at German websites...
Actually, Google translate handles it quite well.

As for the moar powar, I might be getting donations from a capacitor company to allow about 2 kJ of stored energy. Still comparatively low, but it would allow me to scale things up a bit.

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