Dave H. wrote:
Evening all, nice out, isn't it?

I'm hoping to pick some brains, I recently acquired an ancient and abused
[1] Challenger lathe[2], mainly for the tooling and motor that came with it,
and I think I'd like to get it running to get back in the hang of machining
while I find what I'm actually looking for (a Holbrook would be nice...) at
a price I can afford!

Being a fan of skips, the dump etc. I came across an old Audi air-con pump
complete with electromagnetic clutch for two quid[3], dismantled it and
found it's pretty simple to adapt (apart from the spline in the hub, would
have to bore it and cut a keyway) - I believe that these are called on to
transmit upwards of 5HP (certainly putting 12V at 4A up it locked it pretty
firmly), it occured to me that I could use this as a drive clutch for the
3HP (eek! possibly a bit over-sized for a small lathe...) single-phase motor
that came with the lathe, on either the motor output shaft or the
countershaft-that-needs-to-be-built, can anyone see any glaringly obvious
snags that I haven't?

I've had the motor connection box open, and have sussed out how to reverse
it, should I want to, but would like the added safety of braking it - I've
seen a few references to DC braking, wonder if anyone has had any practical
experience of it? I assume that it's just a case of dumping Several Amps
into the motor coil and letting back-emf/induced current in the rotor drag
it to a halt?


You want to use if for a drive clutch, or a motor brake?
If a drive clutch, that coil may require up to 30 amps of 12V.
Not sure what you would gain by adding a clutch