Electrical Retard NEEDS HELP!

[pickinfred]

Earl you sure have a "LOT" of useful information tossed at ya on this thread, have you considered using an old bicycle crank and chain. "If you want the lathe to turn faster"......."pedal harder".

Might save you a trip to the gym like....oh ....whats his name?..... and a bunch of electricity.

[Scooter Bob]

Earl, contrary to what others have said, and since you want to vary motor speed instead of changing the step pulleys, I think you are spot on with the DC motor and speed controller.

 

If you start turning down the speed on an AC induction motor with a VFD (variable frequency drive, alters the 60 hertz that we have at the wall outlet) you will start losing torque, and at the lower speeds is where you don't want to be losing torque.

 

The DC motor will give you full torque throughout the speed range.

 

Also, an industrial PMDC (permanent magnet direct current) brushed motor will last you a long time. We have 1/2 hp motors running conveyors at work and I think the brushes last a year or more and they are running for most of the year. And then you just change the brushes for a few bucks. If you get a motor with a TENV rating (totally enclosed non vented) it will not overheat at lower speeds. They are made to do this.

 

Gearing will be another issue. I think those lathes belted the motor to a jackshaft, and the jackshaft had the first step pulley on it. If this is the case, and the ratios can work out, you may lose a little drag if you can eliminate the jackshaft and belt directly to the spindle pulleys.

 

Most PMDC motors you will find will have a max speed of about 1750 rpm. How does this compare to the old motor. Unlike an AC motor with a VFD, the DC setup will not go over the rated motor speed.

 

You can find more info about the motors and controllers at Grainger, McMaster-Carr, Baldor, Leeson, Bodine, and others.

 

You're going to find the electrical part is easy, AC single phase 110v or 220v L,N,G into the DC drive controller, and DC + and - out to the motor.

 

Getting the motor mounted and getting pulley ratios at a good spot will take most of your time.

 

Feel free to give me a call if you would like to discuss further, I do this stuff at work all the time. My number is in my profile.

 

Later, Scooter Bob

[skydoc_17]

First off, I apologize for using the term, "retarded". I grew up in a time when, if you did something "not very well", and despite your best efforts, you continued to do it "not very well", you were deemed "retarded".

This lathe is in my Machine Shop building. I have 115 volt single phase and 230 volt single phase in this building. (100 amp service) This lathe was running on 115 volt single phase, the motor is a 1/2 HP, 1725 RPMS, and draws 8 Amps. I have attached some old pics of the lathe when I first got it. I would like to remove the overhead pulleys, and power the spindle drive pulley (see pic with red belt) with a DC motor and variable speed control. I have been looking at some used motors and controllers on Ebay, and one of my questions is, 90 Volts, vrs 180 Volts DC. Which is better? Can I get a more reasonably priced controller in 90V or 180V DC? I run Carbide tooling on the lathe, (that's why the old motor died) will 90V or 180V handle a heavier load better. I would like to keep the RPMS of the Spindle in the 300 to 1100 RPM range. Stepping the RPMS just doesn't do it when a few RPMS means a big long stringy chip, or a nice pile of little broken chips.

With this new info, is there someone that can help me fine a Motor/Controller combo that will foot the bill. I have a much larger Le Blond Lathe that is currently down as well due to a burned up Rotary Phase Converter. So, I am without ANY lathe at this present time. I figure it would be less expensive to get the little lathe running first. BUT, if anyone has a 10HP rotary phase converter for sale, I would be interested in that as well.

Please ask more questions, I will do my best to get answers.

Thanks again for the help. (AND the pretend check!)

[dingy]

The frame size of the motor is a critical piece of information.

 

Should be stamped on the tag.

 

It will identify foot print & and a few other needed pieces of info.

 

And face style, C-face or rigid base.

Look at this web site.

 

http://www.surpluscenter.com/techhelp/nema2.pdf

 

Gary

[Flyinfool]

If you double the volts, you cut the amps in half.

Lower amps are easier to deal with.

[Scooter Bob]

The 180 volt system will need to get fed with 220volt ac and the 90 volt system will get fed with 110 vac.

 

Since you think you were working the old motor pretty hard, and you might be losing some torque by eliminating some belt reduction, I wonder if going to 3/4 hp might be a little better.

 

Since you're wanting to eliminate the jackshaft, you'll be making a new motor mounting anyway, so it's not a big deal on frame size. You'll be building a custom mounting anyway.

 

Later, Scooter Bob