Ballistic Stabilization Update

A project log for Coil Gun/Gaus Cannon

A device that uses electricity to propel a projectile at a significant speed.

jeff.ballard.86jeff.ballard.86 06/04/2014 at 02:141 Comment

This will be a short update.  EDIT:  maybe not.

Recently while awaiting funds to buy another SCR and some 10 or 8 gauge magnet wire, I have been experimenting with Ballistic Stabilization.

If you read a few logs ago you may have seen that I purchased a 1/2" diameter 5v dc motor that unloaded can spin up to 12k RPM.  I also 3D printed a motor mount and a magnet holder for the motor.  When I installed this into the poly carbonate tubing without the coil it would spin perfectly.  What im about to say should have been obvious to me, but didnt occur to me until I did it.  When the coil gun was fully assembled I decided to test out my "Ballistic Motor" I would spin it up and then push it forward until about 1/4" of the projectile was inside the coil.  That is when the projectile would slow to a stop and not move.  I dont perfectly know whats going on, but I am assuming it is along the same principle of an electric motor.  My assumption is that the coil and projectile are imparting a generator type effect.  And this is effectively making it really hard to spin my little motor up.

So then I decided, ill use a more powerful motor.  I then disassembled an old RC helicopter, and repeated the experiment with one of its much stronger/faster motors.  Failure.  But this time I was able to take at least one interesting measurement from the motor.  At no load full RPM the motor pulled about .6A at 5v, at full load the motor would pull almost 6A at 5v, and become very hot very fast.

So over the past couple days I have been thinking of going with an even larger brushless motors, I have a couple 156kv 2200kw motors I could use.  This comes with a couple problems: they would require much more voltage and they would also require a simi complicated mounting system.  Lastly I decided to do some research on firearm projectile RPMs. I am astonished to say that a projectile in a modern hunting rifle can see RPMs in excess of 200k.  Even for myself, a person highly knowledgeable with firearms I was really blown away.

So then I thought can I spin a 1/2" diameter steel rod even 100k?  And I thought sure, I can get a high KV motor, give it lots of voltage, and some gears and I could spin it however fast I wanted to.  I didnt think this for long, because I believe that its too complicated, it may not look it but I do believe in the K.I.S.S. principle.

Im thinking I may experiment with some different projectile shapes and try to accomplish some sort of ballistic stabilization in some other manner, it may be revolutionary, it may be barbaric, who knows. 

For those of you who may have skipped down here:

 "To keep a long story short" Spinning a projectile while it is partially in a coil is not an easy feat, and has almost been given up on in its current form.

And again, thanks for visiting, reading, comenting, and whatever else you may do.


Chris wrote 06/23/2014 at 23:37 point
Hey, I found this your post while researching my own coil cannon. I was also thinking about imparting spin on to the projectile for ballistic stabilization. My first thought was to use a motor like what you did. I didn't like the idea of having extra moving parts. Then I thought about taking the motor out all together and building a DC motor stator around the projectile. The projectile will act as the rotor and the stator would create a rotating magnetic field making the projectile spin.

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