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5KJ 4 stage rail gun (complete)

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rp181

Sun May 18 2008, 08:00PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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thanks =) where are the rails? are they on the top and bottom? how does the piece of copper sticking out stay connected to the rails without getting in the way of the projectile?

man thats a good camera, i thought it was rendered =)

ea6b607

Sun May 18 2008, 08:27PM

Registered Member #1320 Joined: Sat Feb 16 2008, 01:31AM
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That's a early picture, the rails weren't on it at that time. The rails themselves are on the top and bottom secured with two part epoxy the little metal tabs where secured with a butane torch and a lot of solder later on (I think your probably won't be able to use a torch on polyethylene on PVC as it melts way to fast). The tabs where connected to the side of the rails so it was impossible for them to touch the projectile. And ya I have a Olympus E-500 and love it. Also PVC will shatter as well so be careful with that. There is a lot of force pushing those apart and even using thick polycarbonate like I did on mine can still be torn apart with an unexpectedly low amount of force.

rp181

Sun May 18 2008, 09:13PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Heres what i was going to do: clamp all the parts together and drill a hole in the center. With the table saw, dado it so the rails slide in (and filler plastic). Before sliding it, the rod would be soldered with a propane torch, away from plastic. Once its put in, and plastic bolted down, then the rod would be sandwiched between the plastic, with some sticking out. Then ide sand te rod flat, so i could put bolts in it.

badastronaut

Sun May 18 2008, 10:29PM

Registered Member #222 Joined: Mon Feb 20 2006, 05:49PM
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Wow!!! That is an awesome setup!

You're injector alone is an impressive accomplishment. 400 m/s is no laughing matter.

Can we see some pictures of that wooden plate? I like how you used sound to measure speed. I have had problems measuring speed with my own setup. Can you make a diagram of where the railgun, microphone, and wooden plate. Equations would be nice too :D

Very cool indeed!

ea6b607

Mon May 19 2008, 02:28AM

Registered Member #1320 Joined: Sat Feb 16 2008, 01:31AM
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Sounds like a good idea rp, but you might need to weld the metal

P1011876

not much of a significant target, but was never meant to be. Still made a neat square hole.

I made this diagram to help to explain the measurement method I used. This will calculate the speed and you can find the distance between muzzle and target and thus can fine speed r=dt.

I used Adobe Soundbooth to measure the time, but you can probably find a free software as long as it shows time and dB

Here's a mockup of my new charging box (I'm going to use Lexan for the final version) weighs 35lbs and has 18ah of battery with 700Watts of 2KVAC/DC or 700watts 110VAC or a combination of the two. Also supplies 24VAC for my solenoid.

Also, I have a question, I have 4 350amp 2KV SCR I got for crazy cheap and was wondering what would be the estimated amount of power I could pump through them before they blow.

Backyard Skunkworks

Mon May 19 2008, 03:00AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Audacity could work for the sound file analysis, best free audio editor out there.

Generally SCRs can take about 8-10 times their rated current for a surge, so they might stand 3.5kA. To be safe I'd keep in somewhere in the 2.#kA range, just parallel them for higher amps (as long as the circuit is somewhat inductive they should all close in time).

badastronaut

Mon May 19 2008, 03:01AM

Registered Member #222 Joined: Mon Feb 20 2006, 05:49PM
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Regarding the SCR's, the answer is not enough to handle your 5kJ cap bank. For pulsed applications, each SCR would be able to handle 3500 amps for under 10ms.

Can you annotate that diagram with actual data? What kind of uncertainty do you have with this method of measurement? How about posting the sound file? :)

What do the rails look like after firing?

rp181

Mon May 19 2008, 03:04AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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O.o where did you get those SCR's? i got a 1200v 200A 5500A surge SCR thats 110$, i had it donated though.

Electroholic

Mon May 19 2008, 03:37AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

badastronaut wrote ...

Regarding the SCR's, the answer is not enough to handle your 5kJ cap bank. For pulsed applications, each SCR would be able to handle 3500 amps for under 10ms.

Can you annotate that diagram with actual data? What kind of uncertainty do you have with this method of measurement? How about posting the sound file? :)

What do the rails look like after firing?

5kJ is actually Muzzle energy, so yea the SCRs will only work once if you put them in the rail gun.
they would work for a mid size coil gun tho.

badastronaut

Tue May 20 2008, 03:42AM

Registered Member #222 Joined: Mon Feb 20 2006, 05:49PM
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Posts: 96

I was looking at your speed measurement diagram, and it looks like that one is the case when the projectile is traveling slower than the speed of sound. I think they should look like these.

The speed of sound is about 343 m/s, and your projectile travels almost twice that.

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