> -> How about using 4 or 5-step pulleys? Not as cool, cause you gotta
> -> stop and move the belt, but it's WAY cheap.
> I'm already using step pulleys. However, I need to vary the speed
> somewhat in between the ranges. And it's not practical to stop while
> doing it. I don't need a *lot* of speed adjustment, but I have to
> compensate for load changes.
What about the "variable diameter" pulley setups? I'm not sure
how they're packaged/mounted for generic applications, but I've
seen them as part of the drive mechanism for lawn mowers and
go-carts. (used a lawn mower like this for many years -- works
The basic idea is a two part pulley, with the two parts set to
move closer to or further away from each other. The two parts
form a V for the belt. Springs pull the two halves towards each
other, and tension between the drive and driven pulleys causes
the belt to ride at various heights, resulting in different
You wouldn't have the exact/absolute speed control of an electronic
control (assuming a proper control, with some feedback circuitry),
but it would provide variable speeds using a fixed speed motor.