RG - Electromagnetic Accelerator.

[kid908]

I haven't been posting here in a while, this school year has been busy. Anyways, I've been building a small railgun for the past month now. It's almost done, I Just need to attach an air cannon to accelerate the projectile prior to having contact with the rails. Reason for this is because the projectile is being welded to the rails and will not move.

Pics:
CAD Design:
http://img198.imageshack.us/img198/5478/minirg.jpg

Power supply:
http://img825.imageshack.us/img825/8889/img00818201104191930.jpg

The Railgun:
http://img821.imageshack.us/img821/8478/img00770201104062108.jpg
http://img24.imageshack.us/img24/9064/img00827201104211812.jpg

140V Test Fire:
http://img18.imageshack.us/img18/6673/140v1.jpg
http://img715.imageshack.us/img715/5105/140v2.jpg
http://img26.imageshack.us/img26/8356/140v3.jpg
http://img855.imageshack.us/img855/1068/140v4.jpg
http://img199.imageshack.us/img199/4827/img00833201104212105.jpg

290V Test Fire:
http://img26.imageshack.us/img26/2716/290v1.jpg
http://img43.imageshack.us/img43/3704/290v2.jpg
http://img24.imageshack.us/img24/9580/290v3.jpg
http://img833.imageshack.us/img833/2096/img00843201104220833.jpg
http://img146.imageshack.us/img146/9564/img00835201104220830.jpg

Vid: Caps charged to 290V
http://batsh1tcrazies.tumblr.com/post/4838053133/railgun-test-fire-charged-to-290v

I'll try to update when I can. Right now I need to design an injection phase for the railgun.

[Kornman00]

Shouldn't the "barrel" be longer for a more stable shot?

[=sw=warlord]

Very nice.
Mind if I make a suggestion?
Try using a metal file on both the nut and the conductor plates to get a smoother finish.
One of the reasons you're welding the metals is because there's too much friction during the firing coupled with the EMI generated heat causing the metals to literally fuse.

[kid908]

@kornman:Yes, that will help, but this is just a small prototype (proof of concept), I really want to build this design, but unfortunately, the cost is 5 to 10 Grand (my estimate).

http://img853.imageshack.us/img853/2678/rgsheet1.png

@Warsaw: I'll try that, but I believe I left enough space considering I can put the rail gun at a 90 degree angle and the projectile will slide all the way through.

[Hotrod]

I can't say I know much about rail guns (or guns in general), but that looks pretty damn awesome. What are you planning to do with it anyway? Or are you just building it for fun?

[=sw=warlord]

@Warsaw: I'll try that, but I believe I left enough space considering I can put the rail gun at a 90 degree angle and the projectile will slide all the way through.

Yeah my main concern is the roughness of the metals as they run along the rail.
I hope you don't mind but I've just made a quick design based on something I had to work on whilst doing my course few years back.
It's a design a tutor showed us that I thought might come in handy for you.
It's basicly a solid metal lump and in no way near accurate to scale or proportion but hopefully I might give some ideas for you when you do get around to making a proper projectile.
http://i51.tinypic.com/14xkrhu.jpg

[kid908]

Building it for fun. If the small one works, I know what I need to change on the larger one and see if I can get donations to build it.

Warsaw, that is actually kind of like how I designed the larger railgun's projectile. Pointed front with 2 points of contact and a gap in the middle. it's not that thin but shape-wise, it's similar.

edit: here's a screengrab of the projectile.

http://img64.imageshack.us/img64/4369/projectile.jpg

[sleepy1212]

how fast do you think you need it to move to keep it from welding?

[Kornman00]

Be careful who you accept funding from :-3

[Warsaw]

Building it for fun. If the small one works, I know what I need to change on the larger one and see if I can get donations to build it.

Warsaw, that is actually kind of like how I designed the larger railgun's projectile. Pointed front with 2 points of contact and a gap in the middle. it's not that thin but shape-wise, it's similar.


Pssst, I'm Warsaw. You've been talking to Warlord. :)

Interesting project. I might suggest that another reason for it getting welded is because it's not discharging fast enough, thus giving friction more time to work because the projectile is not accelerating fast enough. The sides of the nut could also be bouncing against your insulating material as a result of air resistance, slowing it down and giving the emf a chance to melt the pieces together. I think for such a rough concept piece, smoothness is not much a factor. It should still work without welding.

[TeeKup]

Sort of looks like the gun from Metro 2033.

[Bodzilla]

Zap~

[kid908]

Pssst, I'm Warsaw. You've been talking to Warlord. :)

Interesting project. I might suggest that another reason for it getting welded is because it's not discharging fast enough, thus giving friction more time to work because the projectile is not accelerating fast enough. The sides of the nut could also be bouncing against your insulating material as a result of air resistance, slowing it down and giving the emf a chance to melt the pieces together. I think for such a rough concept piece, smoothness is not much a factor. It should still work without welding.

I swear I was talking to you yesterday :?

This is as fast as it will discharge. There is absolutely no resistance outside the wire and switch.

I'll try to get it moving with an initial velocity and see how it goes. That may be one reason, but there's no real way to tell.

[Amit]

Isn't this dangerous?

[TeeKup]

Only to whatever is standing in front of it.

[=sw=warlord]

Isn't this dangerous?

http://images2.memegenerator.net/ImageMacro/6833181/FOR-SCIENCE-YOU-MONSTER.jpg?imageSize=Medium&generatorName=GlaDOS

Yes very, Milliamp will make the muscles clench, 30 will kill you.
It can take as little as 8 milliamp through the heart to kill you because the heart is a huge set of muscles and current running through it causes de fibrillation.

[kid908]

Isn't this dangerous?

Yes it is extremely dangerous. The current, even for a fraction of a second, is upwards from 300A. Keep in mind that .07A, or 70mA, going through the heart will kill you.

Also about that volt driver in metro. They shouldn't have used metal bars to bridge the 2 rails, that would case a close loop that does not include the projectile and would not accelerate the projectile. Sound of fire is also off but looks cool.

Charged it up to it's maximum voltage rating 450V and tested to see what would occur.
http://img714.imageshack.us/img714/6421/450v1.jpg
http://img863.imageshack.us/img863/5113/450v2.jpg
http://img709.imageshack.us/img709/9760/450v3.jpg
http://img703.imageshack.us/img703/9549/450v4.jpg
http://img856.imageshack.us/img856/9109/450v5.jpg
http://img215.imageshack.us/img215/6400/450v6.jpg

Discharging residual charge that built back up in the capacitors around 80V.
http://img192.imageshack.us/img192/9375/80v1.jpg
http://img189.imageshack.us/img189/2350/80v2.jpg

[EX12693]

You think there's a better way to get rid of the residual charge... than a hammer?

[kid908]

Ye, I could use a resistor or leave the volt meter connected so it will dissipate it over time, but it's more fun using a hammer.

[Warsaw]

I swear I was talking to you yesterday :?

This is as fast as it will discharge. There is absolutely no resistance outside the wire and switch.

I'll try to get it moving with an initial velocity and see how it goes. That may be one reason, but there's no real way to tell.


Perhaps internal resistance of the capacitors is doing it?

I don't know. It just seems very unlikely that its the finish on your rail and projectile that is causing the welding of the two together. Maybe it's the shape of the nut and how it conducts the current through it.

[Patrickssj6]

http://images2.memegenerator.net/ImageMacro/6833181/FOR-SCIENCE-YOU-MONSTER.jpg?imageSize=Medium&generatorName=GlaDOS

Yes very, Milliamp will make the muscles clench, 30 will kill you.
It can take as little as 8 milliamp through the heart to kill you because the heart is a huge set of muscles and current running through it causes de fibrillation.

That's not entirely true. The frequency will kill you....50hz and positive/negative currents have biological effects on your heart. In DC you can survive up to 300mA if you are lucky.

[=sw=warlord]

That's not entirely true. The frequency will kill you....50hz and positive/negative currents have biological effects on your heart. In DC you can survive up to 300mA if you are lucky.

The body can survive 30K amps [lightning isn't what normally kills] as well but that's not my point.
From what I learned whilst doing my health and safety course 30 milliamps through the heart has the capacity to stop it.
Considering the majority of your body is saline which is conductive it's safe to assume that current will fuck you up in ways you could not imagine.

[kid908]

I'll have a couple of 1second time exposure shots up soon from a dslr instead of crappy vid screencaps.

rule of thumb in DC circuits is 65mA is lethal. It does depend on where but never touch 65mA. Just because you can survive 30K amps doesn't mean you go around touching every electrical shit.

As for AC, I'd say the amps is the same except the frequency will cause extreme muscle contraction that the heart will just not beat. I've had 50hz go through my body in physics class, and it burns at higher voltage (stopped around 15V). 50hz won't cause complete muscle loss at that low voltage though.

[=sw=warlord]

rule of thumb in DC circuits is 65mA is lethal. It does depend on where but never touch 65mA. Just because you can survive 30K amps doesn't mean you go around touching every electrical shit.

As for AC, I'd say the amps is the same except the frequency will cause extreme muscle contraction that the heart will just not beat. I've had 50hz go through my body in physics class, and it burns at higher voltage (stopped around 15V). 50hz won't cause complete muscle loss at that low voltage though.

Which is exactly my point.

[Patrickssj6]

My point was that at low amps the frequency has a more severe effects than the amps themselves. You did not get my point. Thanks.

Not to mention the duration etc.

[=sw=warlord]

My point was that at low amps the frequency has a more severe effects than the amps themselves. You did not get my point. Thanks.

Not to mention the duration etc.

I got your point exactly, do not misunderstand that.
My point is higher amps do in fact cause more strain on protein due to the amplitude of the current.
Apparently you cannot read what I wrote in my previous posts in that it only takes low amp current to kill.

[kid908]

http://img269.imageshack.us/img269/460/img0023wt.jpg
http://img692.imageshack.us/img692/4654/img0035csy.jpg
http://img31.imageshack.us/img31/9528/img0040ib.jpg
Last image is a favorite of mine.

Just for fun:
http://img848.imageshack.us/img848/763/img0024vf.jpg

[Dwood]

Nice shots bro!