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Im pretty new to the whole coil gun idea (and this site), so hi all and heres a few questions :)
Iv got 6x 63v 15000uf capacitors sitting in my garage (162 joules total). I know these are a bit low voltage for a high powered coil gun, but would they be enough to at least shoot a nail through a sheet of paper?
Will i need a very long coil to accelerate the projectile slowly over a long period of time due to my large capacitance?
Should i link the capacitors in series or parallel?
What kind of coil resistance should i be aiming for?
Am i right in thinking a mechanical switch would be sufficient at the moment?
the capacitors are made by BHC DS 515 063 M11 AHS (serial number i guess) 8640 (?)
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
big5824 wrote ...
Im pretty new to the whole coil gun idea (and this site), so hi all and heres a few questions :)
Iv got 6x 63v 15000uf capacitors sitting in my garage (162 joules total). I know these are a bit low voltage for a high powered coil gun, but would they be enough to at least shoot a nail through a sheet of paper?
Will i need a very long coil to accelerate the projectile slowly over a long period of time due to my large capacitance?
Should i link the capacitors in series or parallel?
What kind of coil resistance should i be aiming for?
Am i right in thinking a mechanical switch would be sufficient at the moment?
Would it be possible to feed the capacitors into a transformer before the coil so that the coil voltage is higher than 60?
the capacitors are made by BHC DS 515 063 M11 AHS (serial number i guess) 8640 (?)
Welcome to the board.
Check out Barry's Mark 2 (http://www.coilgun.info/mark2/home.htm). That accelerator used similar capacitors(2x12000uF) and he achieved 7.85m/s with a 45mm long piece of 1/8" diameter welding rod(55V initial capacitor charge).
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
guitardude012 wrote ...
Welcome to the board.
Check out Barry's Mark 2 (http://www.coilgun.info/mark2/home.htm). That accelerator used similar capacitors(2x12000uF) and he achieved 7.85m/s with a 45mm long piece of 1/8" diameter welding rod(55V initial capacitor charge).
Good luck on your coil gun.
What he said, yes. And welcome to the board!
Barry Vendi, Vidi, Velco -- I came, I saw, I stuck around
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
Actually, at full charge the caps would be 178.6J.
If you series all six caps you'd get 2,500uF at 378WVMAX, a real respectable voltage. Just make sure the tollerences are pretty tight (not +/-20%), and seriesing them will work fine. If you do go for parallel, the biggest enemy will be resistance! You'll want well under half an ohm for the coil for decent speed. Don't worry about making the coil that long if you keep resistance low.
And remember to have a high current diode across the coil, opposing the charge of the caps. This will kill the reverse voltage spike and save your caps from a young death.
so if i use them in parellel i should use a very low resistance coil to allow that huge current to flow? but would this risk damaging my capacitors? (since its almost a short circuit)
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
Not 100% sure on this, someone back me up BUT...
I'm fairly sure a near short corcut shouldn't be aproblem so long as you have a good protection diode.
Also remember to shoot for pretty high inductance to get a massive magnetic field.
BTW Ken isn't quite right in the case of coilguns, series almost always yields higher current and voltage, along with shorter rise/pulse times (given the same coil).
thanks for your help so far guys, just a few more questions :)
Im thinking of linking each layer in the coil to a terminal like barry so i can change the number of layers easily. However, what wire thickness should i use to start with? (i will be running the capacitors in parallel for safety reasons, so 60v at 90,000uf). Also do you know what kind of inductance id be getting in that coil with the projectile inserted?
Also do any of you know what kind of velocity would be a good target for me? and what length pulse would be best for a gun of this power? im guessing around 10-15ms from looking at other designs
oh and skunk, what do you mean aim for a high inductance to get a big magnetic field? (i dont understand inductance too well other than that it opposes change in current)
/edit one more question :) do you guys think its worth me trying to use two or three coils? i know enough about general electronics to manage this easily i think, but at these powers is it worth it?
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few questions about making a coil gun
And welcome to the board!
