Whilst searching for an alternative to mounting a Proxon rotary spindle to use for highspeed milling. I came upon an alternative idea whilst building a recumbent trike. What does everyone think concerning the use of either a NuVinci Continusly Variable Rear Bicycle hub or a Shimano Nexus 7 Speed Coaster Hub w/Shifter mounted between the spindle assembly and the motor?
My reasoning is that the motor would be able to run at its peak performance yet one could dial in the necessary spindle speed for the job at hand. Both of these hubs are of a small diameter yet they give outstanding performance and both can handle axial aswell as torsional loads. With ribbed belts they would be able to withstand the necessary loads that are needed for milling hard steels and the speed necessary for machining alumnium and plastics.

I have recently started working on a conversion of a Sturm-Archer 3-speed hub. I found that I can change the operational speed of my milling spindle on the fly with no loss of operating torque. Also, I found that I only have to construct a 3.5" diameter outer housing to contain the drive components. I'll post my results in the new year as well as a drawing of this modification.

They're available on Ebay for $332.99 U.S. and they list for about a hundred more at most bike shops.

The Sturm-Archer 3-speed hub is easily found on older bikes that had the coaster brakes and can usually be picked up for under $5. So far, I've taken a couple of older ones apart and found that the body can be replaced with a 3.25" housing that would also incorporate the drive gear. The only thing that I have left is to work out the internal mods of the housing as well as the spindle connection. I will definitely post a drawing of the project when completed.