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deth502

Fri Feb 06 2009, 01:00AM

Registered Member #1961 Joined: Fri Feb 06 2009, 12:45AM
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Posts: 4

hi, new here.

ok, let me start with an intro. im not much into "this stuff", my understanding of electronics is mediocre at best. i am however, into gun smithing and making. there is a contest on another gun building forum getting started. for some reason, i decided to go WAY "out of the box" and im thinking of building a coil gun.

now, while this post may, depending on your view of it, be breaking some of rule pt 2 section b and c (yes, i did read the rules) im looking for some guidance.in my defense, in regards to sec b, i did do some research on it, and it led me here. you guy seem to really know what your talking about. and section c, im not asking for complete plans, just a good point in the right direction. i know from being on firearm forums how annoying it can be when some newb idiot comes in asking the same newb idiot questions, but please bear with me.

other than the basic principle of using a solenoid to pull a metal projo through a "barrel" and launching it, i dont know much about this subject. what are some good resources that i can be looking at to get an idea of what im going to need to do, and what i can expect. im not looking for 300 win mag performance, but something ion par with a decent pellet gun would be great.

im only looking for something basic here, and looking around, alot of stuff here seems to be over my head.

any help, links, tip or pointers on getting started fro a newb would be much appreciated!!!!

thanks in advance for your help.

rp181

Fri Feb 06 2009, 04:12AM

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

Some great resources:
Barry's website. This site has lot's of low power designs, with great theory.

This site has more higher power portable launcher's. Good from a design point of view, but not very good to learn about them.

Here is my site, It's is for a higher power coilgun (not completed). It has some basic electromagnetic theory:

This site is GREAT if you are looking for a high efficiency design. Lot's of experimental designs.

Also check out the 4hv wiki article, as well as wikipedia's article.

There are always question's on switching. First, figure out how much power you wan't to use. Expect a maximum of 1% efficiency for a basic design. To calculate a capacitor's stored energy, Use the formula: (voltage^2 * capacitance(F))/2 To get joules. Use some basic equation's (im guessing you know them from the gun's) To calculate the energy of a projectile of a given weight and speed (m/s). For any power, SCR's will be the best (price vs. performance). Google silicon controlled rectifier for more information on these. Also on Barry's site, look for his RLC sim, it will tell you a expected peak current, helping you choose a SCR. For a fairly high power coilgun, a cheap source of capacitors is:

They sell individual too. Those store 312 joules each.

If you are trying to impress, and have money, you could always do a railgun =p

Good luck!

deth502

Sat Feb 07 2009, 04:34PM

Registered Member #1961 Joined: Fri Feb 06 2009, 12:45AM
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Posts: 4

thanks for the help!!

lots of good info there, but looking at your page, i think i might be changing directions.

the etg is a concept that ive never heard of before, and im quite intrigued!!!

but im not through looking at the coil gun yet, but i had always thought that a coil gun and rail gun were the same thing?!?!

got more research to do.

rp181

Sat Feb 07 2009, 08:00PM

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

look at wikipedia. Railgun's are MUCH more complicated (in mechanical aspects, electrical is easy, coilgun is more electronic). They also require more money, and higher energy to get decent results. Im only able to do a 5kJ one soon through company sponsorships.

ETG's are nice, but i would still go with coilgun (coilgun is my favorite). ETG's are much simpler. On mine i used aluminum foil, but powder will work many times better.

Barry

Sun Feb 08 2009, 05:35PM

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

rp181 wrote ...

For a fairly high power coilgun, a cheap source of capacitors at Alltronics:

Good find, only 2-cents per joule. It doesn't get much better than that.
My rule of thumb is that anything under 10-cents per joule can be worth considering.

Cheers, Barry
Attaching the electrodes of knowledge to the nipples of ignorance.

rp181

Sun Feb 08 2009, 05:56PM

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

Also, try to find a surplus store near you. Some places are extremely cheap, but other's are inflated.

deth502

Mon Feb 09 2009, 06:50AM

Registered Member #1961 Joined: Fri Feb 06 2009, 12:45AM
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Posts: 4

ok, now i know the actual difference between a coil gun and a rail gun.

also, i notice alot of the term gauss gun being interchanged with coil gun, again, im far from an expert, and while i agree, technically, a coil gun does use magnetics, afaik, a true gauss gun is just a magnet chain accelerator, with no electricity involved (??)

while i dont think a coil gun would be beyond my capabilities, after learning a little more about what i was looking for, i searched coil guns and the new to me concept of the "etg". by watching videos, most coil guns ive seen seem quite anemic, but ive seen video of an etg go through a solid 6" cement block, and then some. now, ive also heard scary things thrown around like "$30k in caps" which i didnt find relaxing, but i would think it would take much less energy to get the same results with an etg than a coilgun, or am i barking uo the wrong tree here??

another thing im liking about the etg thing, is that id imagine i could use a 223 rifled barrel that i already have, and use some of my 55gn fmj projectiles and get much more accuracy out of it that if i had a non metallic coil gun bbl that would have no way of imparting a spin to the projectile to stabilize it in flight, without making labor intensive specialized finned projectiles.

deth502

Mon Feb 09 2009, 06:55AM

Registered Member #1961 Joined: Fri Feb 06 2009, 12:45AM
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Posts: 4

oh, a few more things, i see on alot of the coil guns, thing like "6 layers" and such are mentioned.

does that mean that the magnet wire is only laid on 6 wraps deep?? that dosent seem like much to me, considering the amount of wraps ive seen on things like automotive solenoids and such.

also, with an etg, id imagine that both poles of the electricity must be completely connected with the alum powder?? i dont know if im explaining this well. its not a spark igniting it like an ic engine, right? there has to be an actual complete physical connection between both poles by the "fuel", right??

rp181

Mon Feb 09 2009, 01:00PM

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

I think the powerful ETG you saw was larda's (or larsE's) he is sparsely on this forum, and more active on spudfiles.org. His bank is worth that much, but he was lucky to get those cap's for a few dollars each. When it says 6 layers, that means there are a certain number on windings on the barrel, and those same amount on top of the previous layer. It is what gives the coil thickness.

For the ETG, you are right. On the large one you saw, he used a HUGE relay.

Quantum Singularity

Sun Feb 15 2009, 06:11PM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

deth502 wrote ...

oh, a few more things, i see on alot of the coil guns, thing like "6 layers" and such are mentioned.

does that mean that the magnet wire is only laid on 6 wraps deep?? that dosent seem like much to me, considering the amount of wraps ive seen on things like automotive solenoids and such.

As you research more and more about coilguns, you'll probably find the more powerfull ones have the fewest numbers of turns. I've launched stuff before using various coils of only about 10 turns and one layer total. Yes a small solenoid rated for continous duty on low voltage and low current will need many turns of wire. However pulse thousands of amps or tens of thousands of amps in quicker than an eye blink and you need fewer turns.

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