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Registered Member #1329
Joined: Mon Feb 18 2008, 07:31PM
Location: Harwinton Connecticut
Posts: 53
Hey Guys,
Got my induction launcher working pretty well. Here is the deal.
I wound a flat pancake coil from #12 wire. I used compact discs as the for. The hole in the center is just about 1/2" The coil is glued down to a very heavy and solid oak block for stability.
The power is 4 x 2400 uf @450 volt Mallory caps and the SCR is ... well a block type.
The projectile for this test is an aluminum ring 2" dia x 3/8" high with a wall thickness of about 1/8"
When charged to 500 Volts the ring lifts off and nearly goes out of sight. And it goes very flat or evenly, no tumbling until its back on its way down. Even then it always hits on the edge when it lands.
After using a stopwatch to time the ring from launch till the ping when it hits the ground we, my son and I had an average flight time of just a shade under 5.5 seconds.
What a rush !!!
So now I am wondering about the same things that one wonders about when building a coil gun. Is there some ratio of coil diameter to projectile size and weight I can use to optimize this? Tomorrow I will check out the current amplitude and pulse length on the storage scope.
I looked in the archives for info on this but there is not as much experimentation on this launcher as there is on a coil gun. However I did read that someone had written a simulator.
Any help on finding documentation on this would be great.
I will put some pictures of the crude set upon my website as soon as I can. Can anyone glean any approximations on how high its going by the flight time? Not sure how much of the trip is up and how time its falling. One more comment, after leveling the coil, and if the wind is not blowing, the ring returns to the ground within about a 5 foot radius.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
Paul, great to hear you got your launcher to work so well. If you are interested in digging into the theory, I have two links for you. First check out the homepage of the member WaveRider here he has done some extensive simulations on reluctance coilguns, but his models apply to inductance launchers aswell.
Also, make sure you check out the thread just below this, where I am deriving some simple formulas to estimate the efficiency. Not quite as advanced as Bill's stuff, but it may be a good start.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
w1vlf wrote ...
Peter... I did check out your website and now I see why you were able to come up with that formula for me. Thank you PauLC
This couldn't have anything to do with his interest in Rocketry, right?
Barry, good point. Maybe I don't spend enough time in forums these days. Anyway the thread I was referring to is this and more specifically the rule of thumb formula for efficiency . But since you have spend orders of magnitude more time with coilguns than I have, you probably have some better ideas?
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5.5 second flight time
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