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New railgun project thread with bank contrustion

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rp181

Fri Jan 30 2009, 12:59AM

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

Some of you may remember my old railgun thread. I said i discontinued the project due to cost and availability. Now i am currently making a 5.6kJ bank (thanks christopher karr and christopher hooper!). A company will be donating 2 G-11 garolite railgun enclosure's, designed 2 feet long and with a 1/2 square bore, modifiable to 1/2"x 1/4". They are expected to be here within 2 weeks, which leaves me a week and a half to build it and get some presentable data! Projectile will consist of a aluminum block, and a teflon block for plasma armature. 1 foot of the railgun will be dedicated to accelerate the block for injection. I plan to eventually use high pressure air (co2 sucks!) with a triggered burst disc valve. All the injection systems i have seen, frankly, suck =p. Time on spudfiles helped me =). Triggered burst discs offer extremely fast (sub millisecond) opening times, with no flow choking. Charging will consist of a MOT ballasted on the high voltage side with 1k ohm 300W resistor's (i am currently working on getting that from aonomus). 2 1/0 gauge wire's arrived today that i will be using to deliver power ( as well as a power inlet/switch that i can actually trust). more information to come as i remember stuff, as well as pics.

Update jan. 30 2009
The company that is providing the parts asked me to draw the G-11 parts, with tolerances. Here it is:

This will be the injection valve. The ball valve is a safety, the union is the actual valve.

Rogowski coil

1/0 AWG wire for power to rails.

Update jan. 31 2009
Bought the stuff for the injection system today. Chamber's look small, but it gives roughly a 4:1 chamber/barrel volume ratio. I still need to solvent weld it. I can test it when my mcmaster order comes in. The bus bars and other capacitor bank equipment comes Monday (thanks dr.spark!), and probably the capacitors too.
Here is the injection system:

Update Feb. 1st, 2009
Ive just gotten passive integration to work on the rogowski coil, and now 1 capacitor charged to ~160v, 3900uf peaks a lot less. I used a .01uf ceramic capacitor in parallel with the coil, and 3x 510k resistors in parallel in series with the coil. Pictures will come when im back on desktop computer.

I also made a acrylic coil holder, with a 3/4" hole, perfect for those cable's. Here are some pics:
The coil base, integrator, and MIC adapter.

wire exploding:

Comments.questions/constructive criticism (or plain criticism) Welcome!

Update Feb. 2, 2009
McMaster parts came today (most). I got the rust inhibitor for the busbars, 3ft of copper for the rails, nuts and bolts for the railgun, and screws and nuts for the capacitor terminals. The aluminum didnt come for the bus bars, but i got wierd steel things.
Here is all the correct parts:

The steel things that arrived instead of the aluminum:

Dr. Dark Current

Fri Jan 30 2009, 10:04AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

rp181 wrote ...

Charging will consist of a MOT ballasted on the high voltage side with 1k ohm 300W resistor's (i am currently working on getting that from aonomus).

Why not ballast it with a microwave oven capacitor? (or a smaller capacitor if that's too much current) The advantage is that no heat will be wasted.

rp181

Fri Jan 30 2009, 02:39PM

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

I don't have any MOC's =p Im after slow charging, and i have ballasted a MOT before with these resistors. They won't be on for a very long time.

aonomus

Fri Jan 30 2009, 09:48PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Hmm, just a thought, you could always try using 100W incandescent bulbs as a ballast, cheap, available, etc. I'm going to use 100W bulbs as a discharging ballast for my capacitor bank, but they might be able to withstand 2kV internally before you get arcing... of course they might not.

rp181

Fri Jan 30 2009, 10:20PM

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

I already have the resistors, and i have enough for ballast and discharge. I should be getting the plastic parts withing two weeks.

aonomus

Sun Feb 01 2009, 04:53AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

How goes the railgun?

rp181

Sun Feb 01 2009, 04:57AM

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

as a matter of fact..
I just update the first post with injection system. I went out to look for pvc primer and cement. I found the cement, but the primer had all leaked out somehow and dried. i guess i will epoxy it.

...

Sun Feb 01 2009, 05:51PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You can glue PVC just fine without the primer, and you will get a much stronger bond that any epoxy could do. Just make sure that the pvc is clean and dry before you glue it.

So far this railgun is looking great!

Alough one thing I will say, don't get too carried away with your injector. It should serve only to get the projectile moving, the bulk of the energy added to the projectile should really be provided from the railgun, otherwise you will have to call it an electromagnetically augmented compressed air gun

rp181

Sun Feb 01 2009, 06:22PM

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

The gun shouldn't be TOO powerful, the chamber volume is actually pretty small. Also, the higher the injection speed, the higher the efficiency (so ive read), badastronaut was also talking about the injection having fast enough to get the projectile in the rails a decent amount before current gets to high.

big5824

Sun Feb 01 2009, 07:01PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

yes if the projectile starts faster there should be less rail erosion

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