Cursitor Doom wrote:
On Wed, 16 Jul 2014 17:52:32 +0100, "harryagain"
wrote:

You can't vary the speed of and induction motor by varying the voltage.
You can vary it by varying the frequency.
You can buy a motor speed control that does this.
But be sure it is a frequency changer.

They are quite common on new cheap lathes for example, saves having a
gearbox.


I'm suitably impressed by Bob's suggestion of a wormdrive. A simple
and elegant solution to the problem - at least until the next
fault-finder throws another spanner in the works!

But the worm wheel will wear asymmetrically due to the load of a saw.

Gear trains should be designed so that the load wear is distributed
evenly which is why most gear ratios are non integral.