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Posted: Fri Mar 07, 2008 7:28 am
by psycix
WHOA this thing is AWESOME!
You actually built one!
I suggest putting it in combustion however. (or else hybrid)
The pressure is coming from the heat, not from pre-charged presure
Anyways, a very good job done!
Posted: Fri Mar 07, 2008 8:16 am
by Gunner
Do you know the effiency ot the gun? Have you measured the speed?
Posted: Fri Mar 07, 2008 8:22 am
by Jared Haehnel
How much aluminum do you use per shot? Any idea of the velocity of the projectile when it leaves the barrel?
Whats the estimated cost?
Its incredible...I've never seen one in action before... possibly the next generations of spud guns?
Posted: Fri Mar 07, 2008 9:01 am
by bigbob12345
Wow that is amazing.
It seems to be very powerful which I wouldnt have expected but it went straight through the wall of cinderblocks.
How much did it cost to make?
Posted: Fri Mar 07, 2008 9:15 am
by Ragnarok
Jared Haehnel wrote:possibly the next generations of spud guns?
Unlikely. It requires quite a lot of work, and some electrical knowledge to make something like this.
I'm sure we'll see more of them, but I doubt it's going to be the next generation.
If it were to be due to become the next generation, then hybrids would have already become the current generation - and they aren't. The popularity is still with the original principles of pneumatics and combustions.
Posted: Fri Mar 07, 2008 9:54 am
by Rokmonkey
I have to say that is absolutely amazing! I was one to think that rail guns were near impossible, but I think you could do it!
So how long does it take to charge up the capacitors? What are you using to charge them?
Posted: Fri Mar 07, 2008 10:02 am
by Ragnarok
Rokmonkey wrote: What are you using to charge them?
I imagine a Cockroft-Walton voltage multiplier, or at least something similar, which will probably do it in between 10 to 20 seconds, depending on the exact number of stages, and available power supply (don't know much about the world's electrical power grids)
It is however possible he might be using a transformer (but that's a rather less practical solution).
Posted: Fri Mar 07, 2008 10:10 am
by paaiyan

Wow....
How much did it cost, and what kind of tools do I need to do it?
Posted: Fri Mar 07, 2008 10:26 am
by DYI
I second that question, how much did those caps cost, and where did you get them?
I had never expected performance like that, and was amazed when I saw the video. Have you chronographed it to check muzzle velocity? Because it does a lot of damage for its size, and sounds more like a firearm than what I'd expected.
Great job Larda :thumbright:
Posted: Fri Mar 07, 2008 10:39 am
by Jared Haehnel
If not the next generation at least it is an interesting development... one perhaps I can replicate...
Theres a puff of smoke that appears to come out of the back...is that just dust kicked up from the recoil or is it a vent?
Posted: Fri Mar 07, 2008 12:19 pm
by SPG
Holy Mother of Dog!!!!
It's amazing what you can build and how much it'll destroy things, makes me wonder why the military spends millions on R&D.
Posted: Fri Mar 07, 2008 12:44 pm
by MaxuS the 2nd
DYI wrote:I had never expected performance like that
Yeah, I couldn't agree more.
I could never have expected it to be as powerful as that, I couldn't see how so much pressure could be created in such a short time.
Thankyou for sharing.

Posted: Fri Mar 07, 2008 1:04 pm
by SpudBlaster15
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Posted: Fri Mar 07, 2008 2:13 pm
by Larda
I Have not been able to measured the speed yet, Having some problems with the muzzle-flash.
I don't think this will be the "next generations of spud guns", as Ragnarok says you need some more electrical knowledge then for the average spud-gun and the cost is to high.
The price of the capacitors i have is about 30.000USD if you buy them new from a supplier, in this bank i about 10.000USD worth of caps.
Of course i i didn't paid 30K for them, i got them almost new from disassembled equipment for much less.
I use a variac and a microwave transformer with a full wave rectifier and a current limiting resistor to charge the bank.
Remember the safety, the voltages and currents involved is ABSOLUTELY LETHAL ,if you do something wrong then you are dead.
This thing i really loud and it actually its almost louder then a real rifle.
Posted: Fri Mar 07, 2008 2:35 pm
by Fnord
I'm really glad someone finally made an electrothermal gun. In the future we should have a whole section devoted to electrotherm/electromagnetic guns as technology advances.
I can't really think of anything to say about this other than that. You've done a great job on everything here and I can't really think of any way it could be improved.
Questions:
How much powder do you use for a shot?
Do you have to clean the chamber out every time?
Wouldn't it be better to put the bank in parallel for a higher current pulse?
Any estimate on the pressure you're generating?
Also, (I should probably know this but..) what is the point of the current limiting resistor? Do you risk damaging the bank/transformer if you dump too much through them at once?