Simple Current Limiter (LM317)

[BillTodd]

voltage across the coil will also be fixed as V = I x R.

Erm, It's a coil Irving, the R's a Z ;)

The heatsink it's self is 85x90x4mm if you include the cooling fin's it's 85x90x24mm so the fins are 20mm, I do also have a 80mm 12volt fan bolted to the heatsink.

Ah Missed that bit! - Irving's right, that's nowhere near big enough for 4 devices.

Have you got a couple of Intel P4 coolers kicking around? the old 478pin cooler could dump 50-60w with the fan screaming. Using Irving's figures, you could clamp four lm316s to each which, if you ran the limiters in series, would give you the desired voltage drops for one motor.

[edit]if you ran the limiters in series - brain-fart! they're not going to work in series, unless the currents are exactly matched. You'd have to parallel them at half an amp each.