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LAN_403

hotcrazyfruit

Tue Apr 14 2009, 01:05AM

banned on 5/26/2009
Registered Member #1877 Joined: Mon Dec 22 2008, 02:03AM
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how well would a coilgun do, with a 2 inch pvc pipe (very thin) wrapped with 2 or 3 layers of 6 gauge wire, and about 6 inches long. all powered by a 5 kj capacitor bank, i am not sure about the projectile weight, but my aim is to make a coilgun mortar cannon to shoot about 100meters accurately. any tips on how to go about this, as well as suggestions to add to the idea, would be greatly appreciated.

Specs:
6 or 8 guage wire
5kj cap bank
2" x 4' pvc pipe

Thanks,
Nick

Reid

Tue Apr 14 2009, 01:38AM

Registered Member #2064 Joined: Sat Apr 04 2009, 09:26PM
Location: NJ, USA
Posts: 16

dude, I want to see pictures of your finished product, sounds awesome.
Having done some work with long range ballistics, I propose that mounting your mortar on a variable angle chassis of some sort would be beneficial.
I would also forward that you are firing a 1 cal. piece of iron 328 feet, and you could easily break a car or kill someone.

That being said though, I would worry about the heat generated by your coil. you might want to try some sort of liquid or forced air cooling system to protect the coil and the barrel.

hotcrazyfruit

Tue Apr 14 2009, 01:50AM

banned on 5/26/2009
Registered Member #1877 Joined: Mon Dec 22 2008, 02:03AM
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Posts: 147

Reid wrote ...

That being said though, I would worry about the heat generated by your coil. you might want to try some sort of liquid or forced air cooling system to protect the coil and the barrel.

yea, i can blow up small 18 gauge wire with the capacitor bank, so i was considering wrapping some kind of hose around the coil, and flowing water or a heat conductive liquid through it to keep the heat down. also the variable chassis idea is great. and the pvc is VERY thin, on the order of 16th inch think actually, so it will be about 1.875 cal :D
Also, im fully aware of the danger involved, its not like i have any intent to kill anyone/anything with it anyways, other than steel plates :P

Fnord

Tue Apr 14 2009, 01:32PM

Registered Member #2004 Joined: Sat Feb 28 2009, 11:43PM
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I have only a little experience with coilguns, but unless you plan on firing in quick succession I don't think heat will be a huge issue.

If you want to figure it out mathematically, it takes .385 joules to raise 1 gram of copper 1 degree K.
If your coil weighs only 4 oz (112g), 5kj with 100% heat loss in the coil will raise is to about 300F or (420K, ~295 is room temp).
Of course, your coil will probably weigh a lot more than 4 oz, it was just a worst-case scenario. With 6 gauge wire the first layer alone will probably weigh like a pound.

Also, I wouldn't expect really high velocities, but you probably knew that. 4% efficiency will get you 200j, which doesn't really mean much with such a heavy slug.
You could punch through sheet metal or maybe 1/2" plywood with it.
Play around with the coil shape a little for the best efficiency. Normally a short fat coil works the best, with projectile of about the same length.

Fraggle

Thu Apr 16 2009, 12:37AM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

Large bore mortar style coilgun says induction to me. 100m range is peanuts with a big pancake and 5kJ.

hotcrazyfruit

Thu Apr 16 2009, 01:29AM

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what do you mean peanuts? as in a waste of energy? also, the coil will be the same coil parameters as smaller hand held coils etc,, just sized up. i know it will mean more induction because of the increase in amount of copper, but it is not like i am using like 18 gauge and wrapping 300 turns 18 layers thick or anything, so yes, there will be more induction, but i don't think so much that it will just slowly dissipate the capacitor bank.

rp181

Thu Apr 16 2009, 02:01AM

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

peanuts means it will be easy.
For induction launchers, a lateral pancake coil is wound (Like 1 turn, with many layers), with a central rod. A aluminum ring is placed around it, and the power is pulsed.

hotcrazyfruit

Thu Apr 16 2009, 02:24AM

banned on 5/26/2009
Registered Member #1877 Joined: Mon Dec 22 2008, 02:03AM
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rp181 wrote ...

peanuts means it will be easy.
For induction launchers, a lateral pancake coil is wound (Like 1 turn, with many layers), with a central rod. A aluminum ring is placed around it, and the power is pulsed.

o okay, i haven't seen anything like this before. , iv always made my coils with many turns, and 2-3 layers. but ill definatly try it out. what are the differences (i mean in terms of the shape/size/position of the electromagnetic field) produced by a pancake coil?

Fraggle

Thu Apr 16 2009, 06:11AM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

Sorry, that is what I meant - ring launchers are really powerful!

woxxey

Thu Apr 16 2009, 02:56PM

Registered Member #1906 Joined: Sat Jan 03 2009, 05:06PM
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Posts: 39

With 5kj it sounds like you will be doing something quite large, so I'll try to sell you an idea (which I'm quite curious to see how it works):

Unfortunately I've never seen anyone making something out of this, either with bad or good results, but it seems to me like it would offer, sort of, an infinite number of stages at the cost of some extra friction (and copper).

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