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Ring Launcher

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LAN_403

Part Scavenger

Mon Sept 11 2006, 11:12AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Nope. It's steel I think, definitely ferrous. The reason it's there is because without it, I get big peak currents and the ring only just falls off the stand. I originally thought the same as you did.

Marko

Mon Sept 11 2006, 12:20PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I tihik it falls from stand more because is simply loses balance (?).

Peak current can be minimized by adding more inductance, or lowering cap voltage in exschange for capacitance (use more capacitance and no doubler for example).

For your description just couple of 200V 470uF caps would work.

I would put something like PVC pipe in that place

EEYORE

Mon Sept 11 2006, 05:30PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

I built one of these years ago. Used 500volt 3500uF lytics (2 of them for 500volts, 7000uF). I made a flat spiral coil with maybe 20 turns of like 12awg. I used the same ring as you did too. I just layed it on the coil, no rod to guide it. No scr would stand up to it, so I used metal rods to short, caveman style

My ring would go up some 50 feet or more, very loud, and HURTS when it falls on one's head! Eventually, the coil broke from the power.

Matt

Electroholic

Mon Sept 11 2006, 06:16PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

the rod is there to increase inductance and concentrate the flux, like coil gun, there should be a balance between them, and no one can tell you exactly how to achieve the highest efficiency.

Good job, very professional looking.

Marko

Mon Sept 11 2006, 06:43PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Rod is truly a benefit for thompsn launcher (using continuous AC into coil to repel the ring).

Pulsed rgn-launchers can work well witrhout it too if tuned and souped up.

You can come to some serious disk velocities with few hundred joules of energy, but this one is fine as a small demonstrative launcher.

Part Scavenger

Tue Sept 12 2006, 11:00PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Just for the record, I couldn't get it to do hardly anything without the metal rod. I tried several types of coils and wire sizes but nothing worked. I did try a PVC core as well. With the same pulse that will shoot the ring about 6 feet in the air (metal rod) I can't get it to do anything without the rod.

So, if I wanted to get rid of the rod, what would I do differently?

Electroholic

Wed Sept 13 2006, 09:53AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

i dont' think you can get rid of the rod, but you can probably get away with about 1/3 or even less than what you have right now.

Hazmatt_(The Underdog)

Wed Sept 13 2006, 06:22PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

The rod doesn't need to be long because the field drops off as 1/r^2. So by the time the ring gets to the end of your rod it doesn't really feel much of an effect.

My tosser is around here somewhere, probably in the EM projectile thread. Anyway, I get 14' launch from ~160J with a 9" inverted Tee shaped tube. It's Tee shaped because I had to braze a washer to the back of the tube so I could mount it to the wood.

My first version was like yours, only firing in the vertical position. The newer model can be aimed for demonstrations in projectile motion.

My next step is to use an SCR to trigger the gun and to have it uC controlled to fire at 3 different voltages as a demo for kids. They will see how the energy greatly affects apogee in a vertically launched ring gun.

Also, my ring gun uses a hollow tube of steel. If you don't want to use a hollow rod, the best way to go is to fill a hollow tube with oxide coated rods of steel, just like a transformer. The oxide improves performace by reducing lossy eddy currents during the pulse.

Matt

Part Scavenger

Wed Sept 13 2006, 11:16PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

You could do that pretty easily with this one. Just trigger the gate differently than I've got it. I've got a 8 step LM324 based voltmeter that I designed a while back if you want a better meter than this one. Funny, I think I'm finally getting to the point were I can just "build" whatever I want. Sometimes...

/*Digs up pic

Hazmatt_(The Underdog)

Thu Sept 14 2006, 12:51AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

why would you do that?

the lm3915 is a bar/dot voltmeter in 1 chip!!

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