Retrofit variable speed motor for lathe

[Greg Wandless]

I am in a hunt for a varable speed motor suitable to power a homebuilt wood lathe. Anybody have a idea as to where I can get one.

Thanks,
Greg

[Anthony Yakonick]

How much do you want to spend, those things aren't cheap.

[Rob Russell]

One way is to get (4) stepped pulleys and make a stepdown drive.

Use a single speed motor with a 4-step pulley that mates to a 4-step pulley on an idler rod. The other end of the idler rod has another 4-step pulley that mates to a 4-step pulley on the lathe.

This way you'd have full HP through each speed. If you start changing the motor's RPM, you lose power - and you can't change the RPM on a normal, single phase AC induction motor.

Total materials: 4 pulleys, 2 pillow blocks, a piece of round bar stock, an extra belt.

Rob

[Gary]

I make this suggestion in hopes that someone here who really knows about these things will elaborate for you.

Get a used 3 phase motor; there are LOTS of them available for cheap, then get a VFD to control it. You'll need to supply the VFD with single phase 240 volts, it will create 3 phase with variable frequency to control the motor. You should lose very little HP at lower speeds.

FWIW

gary

[Bob Wilkerson]

Without a doubt going with a VFD is the way to go on a lathe. You can pick up small 3 phase motors on eBay very cheaply as well as VFD's. I've bought 1hp 3ph motors there for as little as $35 shipped to the house. When I converted my Powermatic 45 lathe I bought a new TB Woods VFD on eBay for $$175 vs $410 at my local supplier. When searching ebay you'll want to look for the following descriptions: VFD, VSD, AC Drive, Inverter Drive, Frequency Inverter, Variable Frequency Drive, Variable Speed Drive with VFD and AC Drive being the most common descriptions.

If you buy one rated to convert from single phase power you can start with either a 120v or 220v supply depending on the VFD you purchase. VFD's rated for 220 v 3ph supply can also be used by derating them approximately 1/3 from the nameplate hp(amps) rating. The VFD provides forward and reverse variable speed, soft starting, motor protection and removes the need for a magnetic starter all in one package. I have VFD's that will run a 1hp motor from 120v 20A lines as well as 2hp on 240v 20A lines. For larger motors it requires more than 20A of 240v power.

Forrest Addy has a good primer on VFD's at: http://www.practicalmachinist.com/ubb/Forum3/HTML/000002.html

The image below is showing how I mounted the VFD on my lathe. I found it a great way to go!

Bob

<img src=http://www.rgwjr.com/woodworking/ww%20images/PM45%20VSD.jpg>

[Jim Becker]

Originally posted by Bob Wilkerson
Without a doubt going with a VFD is the way to go on a lathe.

Absolutely. Virtually all of the high-end lathes use a VFD system to provide relatively infinite speed control over a range. The VFD system combined with a two or three step pulley system allows for a variety of ranges that can be matched to the project at hand. Further, you don't loose torque when you slow things down. Having this kind of control is particularly important when you start to work with larger turnings. Most pulley-only drive systems do not get slow enough to really turn large blanks safely and sometimes dialing in or out a few RPMs can eliminate vibration very quickly.

[Bill Grumbine]

Originally posted by Jim Becker
The VFD system combined with a two or three step pulley system allows for a variety of ranges that can be matched to the project at hand.

Unless, of course, you want to bypass those old fashioned belt drive machines and go straight to a direct drive VFD!:D :D :D

Bill (who owns two big blue machines from England, one 3 phase, one diesel)

[Jim Becker]

Originally posted by Bill Grumbine
Unless, of course, you want to bypass those old fashioned belt drive machines and go straight to a direct drive VFD!:D :D :D

Bill (who owns two big blue machines from England, one 3 phase, one diesel)

Yea...Poolewood (and the squealing NOVE DVR) are certainly options in this respect...but I would consider that more of a really major retrofit than the original poster was probably thinking about! I wouldn't mind seeing the head of the Poolewood on a Stubby design machine...the latter being the next (and last) lathe I purchase one of these days. Joe Q just got the new short-bed Poolewood in his shop to replace his NOVA and it's a very nice machine, however.