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Quick help with wire/coil

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LAN_403

Gratitude

Sat Nov 15 2008, 05:27PM

Registered Member #1702 Joined: Wed Sept 17 2008, 10:14PM
Location: Ukraine, Kiev
Posts: 33

actually as i remember, Barry sent the post in one thread regarding the coil winding.
he said if we want to make the coil for 100mm with 10 layer, it's better to take 50mm in 10 layer and the rest should be with less layer because of electomagnetic when its flow in wire will prevent the the projecile to take the highest efficiency,
the layer of coil has the peak, and it has some dependencies which directly depend on your fire tube 1-inner and outer diameter,
2-wire gauge
3-layers of wire
4-its very important HOW BIG IS YOUR COIL LENGTH ON TUBE?

anything else, i'm here

Killa-X

Sat Nov 15 2008, 09:46PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Well, Since I didn't know how big to do it and just slapped it on...

First off, Its on an ink pen.

Inner diameter - 10mm
Outer Diameter - ~26mm
Wire Guage - 14
Coil Length - Ink pen size - 79mm
Input Voltage - 1 400v 470uf capacitor
Switching - SCR - Cant give you the speeds unless I re-find it on digikey!

Anything else you need?

Also I took like another coil maybe 20mm but only 2 layers on the same ink pen and didnt get much results. But, its dinky.

How does this wire work? Is it sucky at low voltage and super grande at 400? 100 bad D:

rp181

Sat Nov 15 2008, 11:09PM

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

79mm seems a big long for this power. Try using 1" - 1.5". You projectile should be ~75% the length of the coil, and should just barley be inside the coil.

Higher voltage makes a quicker pulse, so the magnetic field is stronger. I think a good voltage is 300v, up to 1kV. More with large banks.

Any chance for a pic?

Killa-X

Sun Nov 16 2008, 12:00AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

well I'll picture the coil befor I make it into a 1-1.5 inch coil. Should I do the whole 40ft of wire or specific layer count? I'll edit this reply with pictures soon. I'm on my iPod at a wifi hot spot so it might be awhile befor I can send pictures.
also when I make the new coil, I'll be sure to have a rig so the coil is exactly good wounded and flat side. The big one I didn't, and the sides well , curve.

Penny is for reference. Yeah, thats my big crappy coil. No side blockers, first time coiling thick wire, and .. BIG XD I should mention my projectile is about 1 and 7/8 inches long.

guitardude012

Sun Nov 16 2008, 07:40PM

Registered Member #968 Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104

I guess I would have recommended increasing capacitance if your switch can take it. Capacitors are cheaper than 14awg coils =/ example Also something seems off about the solder "pfffing" I would remove the solder from the coil leads, file the enamel off the connection area, and resolder.

Killa-X

Sun Nov 16 2008, 10:45PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

guitardude012 wrote ...

I guess I would have recommended increasing capacitance if your switch can take it. Capacitors are cheaper than 14awg coils =/ example Also something seems off about the solder "pfffing" I would remove the solder from the coil leads, file the enamel off the connection area, and resolder.

Well, It might have been because I cut it, put solder at the very end enamel, and then solder that to the wire. I haven't tryed doing 400V with the enamel actually scrapped off with a razor yet. But yeah, I got 10 of these 400V 470uf capacitors each $1.50, and I've shot 5 of them off at 350V before with my SCR switch so..

I still need to know though, Should I just wind all my coil into a 1.5 inch long coil and pay no attention to a specific layer count until it works?

guitardude012

Mon Nov 17 2008, 12:21AM

Registered Member #968 Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104

I have had success with: 3900-7800uF @ 350v with a coil very close to yours except mine was only 4 layers.

I would leave your coil like it is and use more caps in parallel since you have them. Be careful not to exceed the limits of your SCR. In my case I found in simulation that I was peaking at well over 1kA.

Improvements:
It sounds like you need to resolder the connections to the coil with the filing method I described. I have been careful to do this and as a result have never had the solder joint problems you mentioned. I would file ~1cm of enamel off, then twist whatever wire i was connecting around that 1cm of bare 14awg coil wire and use plenty of solder. When that is done insulate the solder connection(heatshrink?) And test coil resistance with a multimeter. You should see somewhere around 0.1ohms.

First shots:
On the first (half powered?) shot watch the coil carefully for sparks. If you see any there is a problem. You should hear the coil clenching the barrel when you fire, unless it is a ridiculously strong barrel. If you don't have a voltage meter hooked up to the cap bank now is a good time to check that the cap bank discharged to below 20ish volts(if using SCRs) Then after being sure the capacitor bank is discharged check the coil resistance again to make sure the enamel held up. Also watch out for coil temperature and don't fire your high powered shots too quickly after each other. You can repeat this while increasing the voltage. Most of these issues won't show up until you increase capacitance.

Safety:
Obviously, if the capacitor bank is not discharged touching a coil to check temperature with your fingers is DANGEROUS. Trying to feel the coils clench is also extremely dangerous and shouldn't be attempted. In general, I recommend wearing protective clothing(especially when firing a new configuration)in case of wire explosion.

Killa-X

Mon Nov 17 2008, 01:53AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Yeah I put a CD-Case design around it when I tested my small coil. But yeah, the ONLY wires I touch when the bank is charged, is the 9V battery + to SCR gate, since this is just normal 9V battery power. I'll give my larger coil a try again, and maybe even try 2 capacitors. I'll let you know how things go tomorrow.

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