Variable speed motor question

[Duff Bement]

I would like to switch my 1 1/2hp 110/220 volt ac motor to a variable speed . What is the best and least expensive way to do this with out loosing performance. It is currently running it on 110 but I could easily be changed to 220. I am tired of changing the belt all the time and it only go down to 600 rpm. Any help would be appreciated .
Thanks, Duff

[Dennis Ford]

This article should help explain the items needed to install a three phase motor and a variable frequency drive.

http://www.easttexaswoodturners.org/tips-lathe%20motor.htm

If something in there is not clear, let me know.

[Wilbur Pan]

Three phase motor and VFD is the usual way of adding variable speed to a lathe. But if you are looking just to lower your minimum speed, another thing that you could try is a jackshaft. This is basically a secondary pair of a small and large pulleys on an axle that fits between your motor pulley and your headstock spindle pulley. By hooking the motor pulley to the small pulley on the jackshaft, and having the large pulley hooked up to your spindle pulley, you'll slow down the lathe.

Although a VFD/three phase motor set up is convenient, one thing that has to be considered is that as you slow down the RPMs with this type of control, you'll also lose HP and torque. With a jackshaft setup, this won't happen.

[Duff Bement]

Thanks for the input. It looks like a jack shaft will have to do the trick for now. At least I know what to ask for at christmas:D. Is there a good referance somewhere for choosing pully sizes or do i need to dust the cobwebs off my brain and calculate all this stuff the old way.
Thanks, Duff

[Cliff Rohrabacher]

It looks like a jack shaft will have to do the trick for now.

Wilbur's right. Each pulley combination can consume as much as 10% of the power your motor generates.
You can lessen this by using light weight belts and light tension. Flat belts are best at power transmission with minimal power loss.

[Jeff Bower]

Duff, someone gave me this spreadsheet to figure pully size and speed. Sorry to whoever gave me this, :oI know I got it here just not sure from who.