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Registered Member #8497
Joined: Tue Dec 04 2012, 06:24PM
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Posts: 74
Has anyone played with really long coils - I'm thinking 6-12" in length. I understand it would probably saturate the armature, but if the pulse is long enough, even a linear relationship would still produce force.
I've been scrolling through the archives, but haven't encountered anything yet.
Assuming constant current and no saturation, doubling the coil's length will double the resistance, but force will not double. If we take coil with very high length to diameter ratio and double it's length, force will stay almost the same, while heat dissipation will double. In other words, long coils are not efficient.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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Posts: 600
Yes, same even if you keep the length of the wire the same and change the winding pitch, only a short bit near the ends of the projectile will make much difference (inverse square law on each bit of wire). The further away bits will do very little.
So you're burning the same amount of power, and getting less force.
Generally, to a first approximation, you want everything maximally close.
hmm, in fact come to think of it, varying the length of wire (while adding in insulation so as to keep the external geometry the same) have a predictable effect on force? So I guess, that's almost a trivial restatement of what Yandersen just said, pretty much.
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Really Long Coils
