Howdy all,
  My Supermax mill has a busted up pulley in the head.  (not much unlike mine  )
Anyway, it is very similar to a BP Variable type except there is no "step down" on the top of the upper housing.

I want to replace the original motor with an inverter duty motor that I have and use a VFD.
I can easily modify the mounting for this but am looking for advise on what pulley type and size to use.
Should I gear it UP ? or DOWN ? or 1:1 ?   
Single or double V ... or timing type ? Size ?   

 My little 1hp BP (8 speed) only has 1 seemingly small V belt.

It's just 2 HP and the motor is rated to 5200 RPM.
It will also produce 2 HP at very low rpm so I might not even need the backgear but it will be there if I do need it.
Thanks,
Russ

Ok, so I went ahead and ordered 2 double "A" (1/2") V-belt pulleys.
4.25" and 3.75" with taper lock bushings.
They will interchange so I have the option of  1.13:1 or .88:1
Planning to go with the reduction.
Russ

I would go with the .88 ratio too, better to have that little bit more torque than the extra 600 revs. The V belts should run quieter at high revs, from experience tooth belts at above 4000 rpm get very noisy.

But that's only my opinion 

Graham

I highly value your opinions Graham, even when they are in agreement with my own.
Thanks,
Russ
 

I agree, you need the power over the speed.