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Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
I have 14 awg wire, and my current messy'ish coil is like over 6 layers. I've been told buy a guy that knows about coilguns (never knew this) and he said with 14 awg, this is a huge waste of energy, and I should be doing around 2 inch wide, and 3 layers.
I'm asking you guys what do you think I should do? with my current coil, 5 400V 470uf caps at 380V cant even shoot a sharpen nail through both sides of a soda can. And he beleives 2 inch 3 layers will really kick up the power..
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
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Posts: 135
Well with a 2 inch long coil (and estimated inner diameter of 10mm) 6 layers should give you a pulse period of about 2.14ms (with about 30 turns per layer) personally I think this is too short for such a low power so I would actually increase the number of layers to about 9 giving you a pulse perid of 4ms. Experiment and see what happens, but first what are you switching it with? Because removing layers will dramatiacally increase the current and if you're using an SCR you could ruin it.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529
Heres what i think: Your wire size is way too big for that amount of energy. A thinner wire with ~2layers ~2in long will work well. Roberto is saying to add turns to increase resistance, when you can lower gauge. I use 12AWG with 1kJ, and the coil barely gets warm. Also, based on barry's simulations, a projectile should be 75% the length of the coil.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
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Posts: 135
^^ What guage are you thinking? because with 18AWG it would have a peak current of 4115Amps and a pulse period of only 600microseconds, I doubt that would work well and even if he used 22awg the pulse time is 1 millisecond with 2746amps which I think is still to short.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
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Posts: 137
rp181 wrote ...
Heres what i think: Your wire size is way too big for that amount of energy. A thinner wire with ~2layers ~2in long will work well. Roberto is saying to add turns to increase resistance, when you can lower gauge. I use 12AWG with 1kJ, and the coil barely gets warm.
It's not just whether the coil gets warm after a few shots; the resistance of the coil makes a BIG difference. With my 1903.5J capacitor bank and a 100uH 0.04 ohm 10 AWG coil, the coil dissipates over 50% (!!!) of the input energy (6170A * 0.04Ohm = 246.8V dropped). After realizing this, I decided either to make a coil using 6AWG square wire, or (actually) make a multistage gun using smaller 10 AWG coils.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039
Mind that radial 400V 470uf capacitors arnt really a Pulse capacitor last i checked. but comparing to when i did like 18 layers of 22 guage, at 20mm long coil, my 14awg wire was A LOT better.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
How long is your projectile? This will determine how long your coil should be, your projectile should be about 75% of the length of the coil. I personally believe your coil should be about 1.0mH (This gives a pulse time of 4.8ms and a current of 583A peak) so put all the information into this calculator and it will give you your coil perameters.
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coil suggestions?
