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Railgun begginings and questions

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phil

Mon Jun 09 2008, 11:45AM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

True, it was just a representation not the actual projectile. I calculated that i'll be getting 60J out of those capacitors. Even at 10% efficiency thats still 240Ft/s... basically the speed of a paint ball gun. That render you see a few posts above has about 3 turns per inch, i'd probably go with .5 turns per inch.

OZZY

Mon Jun 09 2008, 12:53PM

Registered Member #511 Joined: Sat Feb 10 2007, 11:36AM
Location: Somerset UK
Posts: 55

Phil wrote:

I calculated that i'll be getting 60J out of those capacitors. Even at 10% efficiency thats still 240Ft/s... basically the speed of a paint ball gun.

Did you mean 600J, I make it 591J. 10% is very optimistic, very few railguns have done better than 2%. Even 600J is very low power for a railgun with 1/2" bore, successful railguns this size use 10 times as much energy! I would concentrate on getting the railgun to work first and worry about stabilizing the projectile after.

ea6b607

Mon Jun 09 2008, 03:16PM

Registered Member #1320 Joined: Sat Feb 16 2008, 01:31AM
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If you have 60 of those I would suggest using as many as possible. I had 5Kj on mine which had a 1/2" bore, and I still felt that I should have put more power into it. Most around that bore have 15-30KJ. BTW all 60 of those capacitors are only 2.5KJ.

Andyman

Mon Jun 09 2008, 07:16PM

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

I don't think that rifling on the projectile will do a whole lot. If you get sufficient power, the projectile will nearly vaporize and the rifling will melt away within the first few inches of the barrel. It would be more effective in a coilgun.

rp181

Mon Jun 09 2008, 10:01PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

ide say try a mini version thats round just to make sure it works. I think it will work, but it wont be as effeciant, since less magnetic fields will interact with the projectile.

phil

Mon Jun 09 2008, 11:18PM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
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Posts: 52

Yes there was a typo in my above post it should have been 600J. And 2%? thats really disappointing actually. Do you think these capacitor would be more suited for a CG rather then a railgun?

ea6b607

Mon Jun 09 2008, 11:32PM

Registered Member #1320 Joined: Sat Feb 16 2008, 01:31AM
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Posts: 67

you should get better then 2%. I'm not sure why everyone has an idea that railguns are so inefficient they usually average from 10-15% with large scale ones such as BAE's having up to 40% the smaller the less efficient generally.

rp181

Tue Jun 10 2008, 12:04AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

i say go for multi stage coilgun, unless you want to buy caps, look for ~450v.

phil

Tue Jun 10 2008, 12:07AM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

I was trying to start small being i've only designed these i've never actually built them. Maybe i'll start with a single stage CG using a smaller bank to just get it working. Thanks for the help so far guys =).

zephir

Thu Jun 12 2008, 06:29AM

Registered Member #1471 Joined: Tue May 06 2008, 03:17AM
Location: Irvine, California
Posts: 13

finally, someone else who wants to build a rail gun to shoot cylindrical projectiles in place of cubes or boxy ones.

I have the same idea, but to save money and effort, I plan on buying pulled bullets. My first railgun would use the cheapest to get .30 cal M2 ball bullets. Its like 50 bucks for a case of them. That's hundreds and hundreds of full metal jacketed (copper), lead cored bullets that's manufactured with precision ready for reloading or other purposes. That way, you don't need to machine anything as a projectile, and recovery of the projectile isn't a big deal either, just buy another case of pulled bullets.

Since your cap bank is larger than mine, I would advise you to buy larger bullets, like .50 cal M2 ball (FMJ, copper, lead cored, 600 grain) or you get even bigger bullets all the way up to .700 caliber. They're quite a bit more expensive, but at least they won't vaporize on the rails.

AS for twist rate, I think 1 turn in 9 inches would be a good point to start at. For firearms, generally its between 9 and 22 inches per twist. The heavier the bullet, the less twist you need.

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