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Coilgun? Induction? Or something else? Answered

Hi, There video above shows a simple coilgun like device that shoot coins.
In my understanding, it looks like a simple induction Coilgun design, since it repel coin away from the coil instead shoot the coin through the middle.
However I have a hard time replicate the result.
I use the same camera with the same capacitor (350V), and also use penny for the non magnetic projectile.
Its the coil part I'm not sure about.
In the video, it looks like a relevantly messy and small coil.
Can anyone suggest me on the coil design for the same result?
Most resources I found are either on reduction design or base on coilgun design instead this simple shooting mechanism.


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Jack A Lopez
Jack A Lopez

Best Answer 8 years ago

The principle at work here is Lenz's law, which is to say the current induced in a conductor by a changing magnetic field, produces its own magnetic field in a direction that opposes the changing field which induced it.

Searching for this phrase "Lenz's law" on Youtube(tm) will turn up all kinds of results. Including the word "jump" gives more of the "jumping ring" physics demos.

Also I found this guy
who likes launching aluminum hard drive platters.

I am guessing the magnitude of this effect is going to depend on the conductivity of the disc, or ring, being launched, and also the magnitude of dΦ/dt.    So if you can improve either of those, e.g. find a coin that is a better electrical conductor, or make your magnetic pulse bigger, or faster.

One way to improve electrical conductivity for many metals is by lowering temperature.  So often times the demo includes some liquid nitrogen.  You know, a lot of stuff goes better with LN2.

For your thing, I'd suggest trying an actual pre-1982 copper penny, rather than the post-1982 ones, which are made out of zinc. That's assuming you're using pennies from the Former US. I don't know what other country's pennies are made out of.

It's not obvious how many turns on the coil would be best.  More turns will give you more field for the same current... but more turns means more resistance, and more self inductance, which makes your weaker and slower.  That guy with the disc launcher, who I linked to above, he was doing some work on coil design, trying to empirically  figure which sized coils worked best.


8 years ago

Your problem may be more associated with the con it's self - Try a bit of aluminum rather than a coin