[jonesturf]

I have a Boss 5. Want to convert it to a vee pulley setup and be able to keep back gear as well as use the original spindle brake. The motor I have is the factory US Motors model that state RPM around 1710. I'm wondering how I should go about arranging the pulleys. Another guy did a similar setup and I was going to source parts like he did from Surplus Center. Tryingt ot figure out on pulley size at the moment. With 1710 RPM I would need something like a 2.47:1 ratio to maintain the orginal 4200 RPM.

I would also like to be able to boost my spindle speed a little too...maybe up to 6k. I know I can overdrive the VFD as well. Will this motor handle it? I was thinking that using the pulleys initially to get me close to the stock 4200RPM and then go up from there with the VFD or am I missing something? I see a lot of guys did a 1:1 pulley arrangement. Wouldn't that only get me 1710 max?

[Al_The_Man]

I see a lot of guys did a 1:1 pulley arrangement. Wouldn't that only get me 1710 max?

Double if you run the motor up to 120Hz, same RPM as a 2 pole motor.
Al.

[jonesturf]

Two pole meaning a 3450 motor, right? Is it safe to run the stock motor at 120Hz?

[Al_The_Man]

I have always run 4 pole motors at 120Hz, I figure most motor manufacturers make both 2 & 4 pole versions and use the same manuf techniques for both, balance, bearings etc.
Al.

[jonesturf]

So in order to get faster speeds I have to either get a different motor and start off faster (which I don't want to do), run the VFD up to 120 Hz, or work with pulleys. Any reason why everyone stays 1:1? I'm guessing loss in torque becomes an issue? Keeping back gear should help with that some though. Would running my pulleys to 3k with a ratio 1.75:1 ratio work and then pick any of the remaining speed up with the VFD or will I have torque issues with that at lower speeds?

Forgot to mention my VFD is a Hitachi WJ200-22.

[Al_The_Man]

I have a couple of XLO knee mills that I converted from varispeed to 1:1 direct, but these have a 6:1 GB also which can be switched in for the low rpm's.
Al.

[jonesturf]

I'm assuming those are with 3450 motors?