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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1715
You haven't told us what you are launching. And it would be interesting to know the DC resistance and AC current drawn by your experimental coils. Can you borrow a clip-on ammeter? Please keep us informed about your further adventures.
Google turned up some references to the standard jumping-ring demonstration: and section 5.4 of
In this configuration an iron core is better than no core, but it will conduct a circumferential eddy current that wastes power. I bet a -laminated- core would be measurably better. DIY possibilities include steel roof flashing from hardware store -- thin sheet metal supplied in a spiral coil, re-coiled around a narrower mandrel with insulation between turns. Or a bundle of insulated steel rods, strips, or wires, or a thick steel pipe with longitudinal slit, or stack of cores -made- for transformers.
Registered Member #2127
Joined: Wed May 20 2009, 03:35PM
Location:
Posts: 8
I have a couple sections of copper pipe, from .25 to 1.5 inches. They just fit around the core with about a milimeter to spare. I tried running more coils outside the blue one, in parallel, but the projectile doesn't go nearly as far. I think the additional coils raise the inductance too much. I have steel roof flashing in my garage, I will try that as a core. I can check the resistance at school. It does get hot quickly, including the core.
EDIT: I redid the connections for the coils, and there doesn't seem to be any difference in using multiple coils. it DOES get hotter, but the height of the projectile stays around 3 ft.
Now I'm wondering if it would work better with a bank of capacitors powering it, and where I could get capacitors by Monday. Would the 330V, 120µF ones in a disposable camera do the trick?
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Coil
