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Railgun fired!

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Railgun fired!

Unread postAuthor: rp181 » Sat Feb 21, 2009 3:11 pm

First off, this is not in m project thread because i did not want to quadruple post....
Second, I accidentally did it without running the program for the rogowski coil !!grr

Now the info:

The railgun was fired today, with one digital camera and a digital camcorder (unable to connect to computer ATM). The injection pressure was probably around 50 PSI.

As most of you know, the enclosure is a 2 piece set, with a half inch bore. The projectile was a aluminum block with a V tail, 1.25" long. The target was a cardboard box packed with paper (for reference, the injection alone barely broke the first layer of cardboard) with a metal plate on the back. The projectile went through all the way, and put a .5" dent in the metal plate.

Here is the interesting bit:
I put a layer of kopr-shield corrosion inhibitor on the rails. When i opened it up, there was almost NO rail erosion. The only damage was a pit with aluminum in it at the very beginning, and a small deposit in the middle. Before i i washed it, there was still a film of the material left. Projectile corrosion was significant, so that will be main point of research from now on.

Im not very good at explanation's, so here are some picture's/video. If you have any questions, ask.

Video:
[youtube]http://www.youtube.com/watch?v=pYQJXB3U12I[/youtube]

Notice two things:
1) the slow falling things. I think that is the plastic insulation on the rails.
2) The cable's. Those where zip-tied with 3 ties, and they still broke!

Pictures:
Image
Image
Image
Image
Image

I have tons of pics, so if you want something in particular, ask.
Video fixed by jrrdw
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Unread postAuthor: jrrdw » Sat Feb 21, 2009 3:56 pm

I don't know much about these, but anything that can lave a square piece of aluminium like that is all right by me. :shock:
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Unread postAuthor: psycix » Sat Feb 21, 2009 4:02 pm

Very nice!
Projectile corrosion was significant, so that will be main point of research from now on.

Injection at a higher speed would do it right?
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Unread postAuthor: Lentamentalisk » Sat Feb 21, 2009 4:31 pm

That last pic is absolutely awesome!
Nice job!
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Unread postAuthor: rp181 » Sat Feb 21, 2009 4:34 pm

@psy: Nope, that just means more wobble. A copper projectile and a railinsulator that is flush with the surface of the rails should help. That shot was packing tape over the rails =)
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Unread postAuthor: maggotman » Sat Feb 21, 2009 6:37 pm

i kno it might seeem like to much effort but would lapping the projectile to the rails help to improve contact
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Unread postAuthor: Lentamentalisk » Sat Feb 21, 2009 6:51 pm

Lapping? you mean like this?
I don't get how you would lap an object to another.

Also, I know it might seem like too much effort, but spelling would most defiantly help with readability, understandability, confidence in what you say being what you mean, and our respect for you.
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Unread postAuthor: maggotman » Sat Feb 21, 2009 7:17 pm

Yeah basically what is said on wiki. My thought on this is because the main problem with rail guns is arcing with mets things. I also think you should use a higher input pressure.

I think on the power labs gun he used something like 500psi.


Lentamentalisk wrote:I don't get how you would lap an object to another.



buy applying grinding paste to one surface and sliding the other one up and down. for a rely good finish i find autosol polish works relay well.
I used it lap the slide valve on my air engine it it forms an almost air tight seal now.
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Unread postAuthor: Fnord » Sat Feb 21, 2009 7:54 pm

I think the purpose of the double tails you normally see on railgun armatures/projectiles is so they can be bent outward slightly to act as "'spring contacts" on the rails.

Awesome gun,
Great Job!


Any idea what this is?
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Unread postAuthor: starman » Sat Feb 21, 2009 8:03 pm

Very nicely done RP! Everytime I see one of these I ask myself why I haven't pursued one...usually the kind of thing right down my alley.

Some schematic diagrams and more electronics detail would be nice.
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Unread postAuthor: MrCrowley » Sat Feb 21, 2009 8:12 pm

Damn that's cool. I'm with starman, seeing these things just makes me want to build one also, though I have little clue as to how to build one.

And that last picture is pretty awesome. :)
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Unread postAuthor: inonickname » Sat Feb 21, 2009 8:46 pm

Awesome. Do you use nitrogen as your injection gas? Also, how many capacitors do you have running it? Sweet job.
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Unread postAuthor: rp181 » Sat Feb 21, 2009 10:36 pm

@fnord
I have no idea what that is. On every recorded bank discharge, I get some kind of purple right before the wash out. If you go to my website, ETG 2, there is a still of one of the most defined purple things i have got. I am assuming it is some kind of UV from the point of contact, OR EM interference. To test the UV, I have some exposed 60mm film, which i will develop at school. It is supposed to be a good UV filter.

@starman and mrcrowly:
I think the main reason that no one builds it is cost. They are quite simple though. If i bought everything used on this setup, it would cost 900 US dollars (not including shipping). I was lucky enough to only spend 50$, and they are all new parts.

The circuit is simple, It is a 3 stage Cockcroft-Walton multiplier on mains, for a Max out 500v. That connect to the bank (takes ~20 sec. to charge), and the bank directly to the rails. When the aluminum goes in, it shorts. I added some resistor's with a switch for bleeding. Ile draw something up now.
@ino:
It is only air from a bike pump (with a high volume Steel barrel.....) I can only reach 60 PSI, i am guessing this shot was around 50 PSI. I want to use HPA eventually (if you have one.....feel FREE to contact me =p), but tanks are expensive. There are 18 capacitor's, each at 400v 3900uf. There is also a small capacitor from the multiplier... Total energy is abit more than 5.6kJ. I hope to expand it over time.

I forgot to mention, there was 24v left after the shot. If you look at the last pic, there are some sparks near the railgun. It turns out when the cable's ripped the zip tie and flung apart, the connection to the aluminum bus bars loosened. The kopr-shield helped.
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Unread postAuthor: jackssmirkingrevenge » Sun Feb 22, 2009 12:15 am

Very impressive, though it seems you're being let down by your injector if it can't go through a cardboard box on air only.
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Unread postAuthor: rp181 » Sun Feb 22, 2009 12:22 am

Naa, I don't want a injector at all, but i don't have the resources for a reliable switch. I opened the target, there was 12 layer of carboard, 2" of bubble wrap, and 2" of packed paper, then dented the back metal plate.
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