Motor Pulley size if using a VFD on a South Bend 10K?

Hello All,

I am a newbie who could use an experienced eye to look over my evil plan to get a South Bend 10K up and running.

It is a South Bend 10K, Catalog# CL 670 Z, Serial number 35702K. I think that means it was made about 1978/79. The lathe is missing the motor, motor pulley, belts, and various mounting bolts.

My plan is to source a new motor- 3/4 HP, TEFC, 1800 RPM.
A VFD- Teco Westinghouse (AC Drive, 1hp, 115V, Single Phase, Medium Duty)
A serpentine belt from an automobile (6 rib, 27/32" wide, 47.5") that will be glued (or sewn together with fishing line)
A V belt, not sure what type or size.
And a replacement motor pulley.

If I am using a VFD do I have to source an original motor pulley (5/8", P/N PT2131K1, 3.956" and 2.237")? Can I just go with a single pulley size (guessing- 2.5")?

The machine is loaded with a thick layer of machine shop grime, but it appears to my untrained and ignorant eye to be in good shape. It isn't rusty, just grimy.

I guess a full felt replacement is in order once I get through the grime layer.

Thanks for any and all advice you can give to help me execute my evil plan!

with you citing a 47.5" belt I have to assume it is a horizontal drive because the UMD uses a ~61" long belt....if that is the case why splice it?

You can use a single pulley, but you'll obviously lose some of the speeds possible. I'd probably grab a single pulley close to the original large size, and find a belt to mate that up to the smaller step on the countershaft. That will give you a range of speeds roughly in the middle of the original speed range. If you need more or less speed than that will give, the VFD should cover the rest.

Once you have it running, you can turn yourself a two step flat pulley for the motor side and use a mini serpentine belt that will restore the original steps if you feel compelled. Sized properly the flat pulley will let the belt work on both steps on the countershaft like the original did.

Although not specifically stated in your original post, I assume you're choosing a 3-phase motor to use with your VFD. Otherwise you'll be missing some wires. Ha.

AFAIK, there were no SB machines that shipped with multiple stepped motor drive pulleys. Once the motor belt(s) are tensioned they stay tensioned until maintenance is needed.

If you choose a motor pulley that's a different size than the original, your spindle speed chart references will be off by the corresponding factor, but only when the VFD is running the motor at 60Hz assuming the new motor RPM is the same as the original motor.

All will work, just might need to do a little experimenting to correlate spindle speed to VFD frequency.

Last thing: The big countershaft pulley grooves are of a specific v-belt geometry profile. Google pulley geometry or sheave geometry and you'll see the options. Your new motor pulley should be of the same profile.

Good luck!

The 10L has a 2 step motor pulley and 2 step countershaft, along with the 3 flats on the cone for a total of 6 speeds without back gear, and 6 more with. I believe the smaller lathes (9, 10K) had the same arrangement. The countershaft pulley was driven by a V belt, but it was actually a flat section so the root of the belt drove the countershaft. The motor side was the usual V arrangement. It was sized such that you could slip the belt off and change the speeds without having to futz with the motor position if you had it set right.

Possible the back mount drives didn't use that, but the underdrive one did.

See this document.

http://www.wswells.com/data/9_workshop/CL670Z_army.pdf

Scroll down to just past the drive assembly parts list. You'll find the motor pulleys and dimensions you need there. look for the part numbers with the NK1 at the end. them the dimensions are given after the part numbers. These pulleys are size for a 5L belt.

Note: I believe the smaller pulleys are normally for the US market. The larger pulleys or for foreign markets with 50 Hz power.

stay safe and have fun.

Joe.


PS, Our thoughts and prayers go out to the victims of the Tragic airport shooting. stay safe.

A fenner V belt of the correct size will allow you to use the original spindle sheave cluster without spindle disassembly. I use a variable speed 3/4hp DC motor with the oem spindle cluster, I use the largest pulley for best belt grip. I was going to go VFD but I found I had the DC unit in my collection. Select the a motor pulley that in combo with the spindle pulley keeps the spindle below the SB max rpm limits, else you will cook the bushings. The low speed limitation will be the 3ph motor itself, potential cogging and may overheat if you dont have an aux. fan for it.

Glenn