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Thread: HELP!! WHAT IS HAPPENING?

  1. #1 HELP!! WHAT IS HAPPENING? 
    New Member
    Join Date
    Jan 2007
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    I have a problem, recently I have been taking part in a scientific project, the project consists in the construction of a one stage coil gun, the idea and principle are simple, we have used capacitors to store the energy and then release it all in one go in order for the concept to work.

    So we have souldered 20 capacitors in parallel onto two long copper wires, we then charge the capacitors (2200 uf 50v electrolytic) and release the charged energy into a coil, the magnetic feild created for an instant pulls the projectile through the coil and launches it, up to here no actual problem.....

    now once done this we started experimenting with two different projectiles, one hollow and one full....as one might expect the full projectile resulted more efficient...... what happened then was that we tried adding more capacitors onto the system, now at that point everything goes weird, the full projectile was projected less further than with 20 capacitors (How does this make any sense?) it is possible that the discharge time for the capacitors became bigger and kept the magnetic feild on after the projectile whent through the coil thus slowing it down........

    This seen we decided to try with 10 capacitors, so once again we souldered these capacitors to copper wires (still the same capacitors) and this time the results were excedingly confusing!!!! The hollow projectile found itself going further (10 cm more) than when 20 capacitors were used!! whereas the full projectile barley reached half the distance it did with 20 capacitors.....What is happening here????: (these measurments were taken several times (I.E. 20) and they all were considerably similar)

    can someone enlighten me?


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  3. #2  
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    You are going through an 'optimum' point, put all the results onto graph paper you'll soon find the best way, also you might want to thinka about controlling the 'on' time of the magnet by switching it with power FETs rather than just letting the capacitors 'die' - that way you can switch off the current when the projectile is at max acceleration and before you start to get 'pull back'


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  4. #3  
    Forum Freshman omerta's Avatar
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    Aug 2006
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    Cincinnati, OH
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    Could the power factor of this capacitive/reactive circuit affect the magnetic properties or does this not apply here? Does phasing (ELI the ICE man) even make a difference here? Seems like it would but then again I'm not sure.

    Sounds like a cool experiment. Good luck with it.
    I've always wanted to know why. Just takes me a little longer than most, lol.
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