Electromagnetic induction questions.


OK, this is another one of those questions I should know, but don't. 

Mainly because I have never done it before, I have a whim to build an electromagnetic launcher, something table-mounted with a range of around 3-5m (10-15 feet).  I'm not after launching nails through Coke cans.

I have been browsing the web, and the designs all seem to be much more complicated than is really necessary for toy.

The image below is a scan of my badly-drawn thoughts of how simple it should be.

  • Have I got that right?
  • I plan to use a bunch of capacitors harvested from dead electronics and connected in parallel.  Is there a recommended total capacitance for such a device?
  • If launching a ring, must the ring slide over the ferrous core, or would there be enough umph to launch a ring balanced just past the end of the core?







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Kiteman (author) 7 years ago
(Oh, and where it says "Transformer + Rectifier", the final product will probably be "wall wart".)
Recommended capacitance is lots.

You really HAVE to couple the core to the ring - the reluctance of the magnetic circuit will be too high to work otherwise.

Steve
Kiteman (author)  steveastrouk7 years ago
OK.

I'm currently harvesting 1000 and 1800uF electrolytic caps from a heap of dead PC boards. Do you think I'll have to pay actual money for some bigger ones?

(Go on, pick a number - how many Farads should I be aiming for?)

The most common method here is to harvest some caps from disposable flash camera circuit boards. 'tis what I did.
Kiteman (author)  Kryptonite7 years ago
I acquired a carrier-bag full yesterday afternoon.
You are well on your way, grasshopper!
I suppose you could take a stab at it from conservation of energy considerations. Assign a speed to the final ring, which has to aquire the energy from the capacitors......
caitlinsdad7 years ago
Coil guns are not toys. You'll put your eye out!
Kiteman (author)  caitlinsdad7 years ago
I want to fire rings or discs from point A to point B, not pierce things.
Given enough oomph (to overcome/work with the many factors involved), the bluntest of objects can pierce anything...

Not that I'm suggesting a desktop coil gun is likely to do anything drastic, if properly built and supervised - and I'm sure you know your class(es) well enough that having such a thing won't give cause for various authorities to become involved.
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