South Bend 16" Under Drive Pulley Size ?

Sachmanram · Jul 6, 2017

I am almost at the end of my refurbishment of the lathe. I believe that the motor pulley and cone drive pulleys are not original, as they only have two "V" grooves, and I think that originally it would have had 3 "V" grooves. I am fine with just two v-grooves, but the spin up seems way too fast to me and I want to be sure that I don't over speed the spindle.

Could someone be so kind as to measure their original V-pulley's OD for me?

Thanks in advance...

Brian

thomasutley · Jul 6, 2017

Check out p. 38 of this doc: http://vintagemachinery.org/pubs/1617/3463.pdf

You should have a 4-groove sheave, although I believe there were a few diameter variations over the years between standard duty, heavy duty, and 16/24 models. My 1943 standard 16" motor pulley measures 3-1/8" OD by 2.42" long (should match thickness of the big countershaft sheave, of course). I should note this pulley is not original to the machine so it may or may not be what shipped from the factory. If you're off a hair on size, it really affects only the RPM chart. It has no effect on feed per inch or on threading which are determined downstream from the spindle via gearing.

I believe the original sheave groove geometry would have been classified as a "4L" (Google v-belt geometry). Looking back, my Amazon order history says I bought a set of four Bestorq A45 (4L470). So far no issues.

v8packard · Jul 6, 2017

Brian,

Which motor do you have? I guess I could look back at your thread..

Marc

Sachmanram · Jul 6, 2017

Thanks for the replies, fellas

I think that the motor pulley might be close to the original OD, but the drive pulley for the cone shaft, I am unsure of. The original part # is AS2547FH2 but provides no reference as to the OD.

I realize that it would not affect the gear train, but it might be running too fast for the cast iron bearings.

The motor that came with this lathe is not original, and was poorly cobbled together. I have replaced it with a 3 hp 3 phase motor.

Brian

thomasutley · Jul 6, 2017

Brian, in that case I would recommend focusing your energy on programming a VFD to limit top speed of the spindle. It's an easy way out of dealing with belt drive ratios and you get the added bonus of variable speed, whether your power input is single phase or three phase.

BTW, you can get a very accurate laser reflective type tachometer on Amazon for <$20 delivered. It's very handy for checking actual spindle speed, VFD or no VFD.

v8packard · Jul 7, 2017

FYI the driven pulley on the countershaft of my 1946 16 is 12 inches in diameter. Does your motor have a 1 1/8 dia shaft? Is it 1800 (1725) RPM, or 1200 (1120)? A 1943 machine was originally set up for a 725 top spindle speed, with a 274 rpm countershaft. There is mention in several catalogs of higher spindle speeds being available on special order, but I don't know exactly what speeds or how it was done in that year. Eventually the bronze spindle bearing 16 could be ordered from the factory with a 1200 rpm top speed. Probably more speed than you want with iron bearings.

The VFD may just work out perfectly for you. I have also been looking into a tachulator that I could incorporate into a DRO screen. Haven't worked that out just yet though.

Marc

Sachmanram · Jul 8, 2017

v8packard said:
Brian,

Which motor do you have? I guess I could look back at your thread..

Marc

It's a German made motor, 3 hp 3-phase, 1735 rpm.

Brian

v8packard · Jul 8, 2017

Brian,

That motor will need a 1.9 in diameter sheave to run the countershaft at 274 rpm if you have a 12 inch pulley on the counter. That is going be tough to find, if not impossible. A VFD might be in your future.

Marc

Sachmanram · Jul 20, 2017

Well, I have a 4 1/4" pulley on the motor shaft and a 7 3/4" pulley on the cone pulley shaft. No wonder it seems to run fast....

Brian

v8packard · Jul 20, 2017

Brian,

If my math is right you are running the countershaft at 1017 rpm.. :eek:

With that motor and 4 1/4 pulley you will need a 27 inch pulley on the countershaft to get it to 274 rpm, or an 1.125 in pulley on the motor. Yikes.

If you can get a 12 inch countershaft pulley you will be running the shaft at 614 rpm, still over twice what was run originally. That may be manageable with a VFD. Not sure about torque though.

Might you have a motor that runs at 1150 rpm, or slower?

Marc

Sachmanram · Aug 1, 2017

v8packard said:
Brian,

That motor will need a 1.9 in diameter sheave to run the countershaft at 274 rpm if you have a 12 inch pulley on the counter. That is going be tough to find, if not impossible. A VFD might be in your future.

Marc

Hey Marc,

I had already adapted the shave to the metric motor shaft by turning a bushing, complete with a keyway slot to fit the shave. I managed to find both a 12" and a 3 1/4" double "V" pulleys at the local Princess Auto store. I have yet to install them to see how it runs. It was vibrating quite a bit when I ran it last, and I could see that there is a hairline crack in the cone pulley casting that I need to have fixed.

Brian

v8packard · Aug 1, 2017

Brian,

Those pulleys bring the countershaft down to 470 rpm. This is a lot closer to what you need, but still a bit fast. Maybe if you keep the belt on the larger steps you will like it. I am curious to see how this works for you. I wonder if the 2 grooves will transmit the full torque adequately..

Marc

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