I know little about proxys, the only time I have used them they just attached to
a counter.

I want to have a 3' vertical track that a standard 5/8" washer slides up and
down. A wire will pass through the washer. As the wire is pulled on, the
washer will go up the track and near the top it will pass a proxy that will
activate a relay that will turn on a 3-phase gearmotor to feed the wire.
(Actually, the relay will trigger a magnetic starter) As wire is fed, the
washer will slide to the bottom and pass by another proxy that will turn off the
relay and kill the feed gearmotor.

I know I need shielded induction type proxys but I don't know: AC, DC, PNP,
NPN, 2-wire, 3-wire, 4-wire or any of the variables. I don't know what
extraneous electronics is needed. Is there a simple/cheap way to do this? Of
course, I can do this with limit switches but I hope the proxys will last longer
and be more reliable. I have to build 9 of these feeders so cost is a big
issue.