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Variable Speed Motor Ideas

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Chewy

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#1
Background: I bought a used Craftsman Wood lathe for wife. 12" swing and 4 speeds. The 1/2 hp motor developed starting problems, so for now it is under the bench and replaced with a Harbor Freight 1/2 hp motor. I am trying to work out the best possible way (and cheapest) to go variable speed. She wants to do off-center and off-balance turning in the near future. Haven't dissected it but pretty sure the HF motor is brush-less., so that eliminates a VFD since that say they only work with brush motors. Thinking about a 3/4-1hp 3 phase motor and a cheap inverter from EBAY. Suggestions about how to best do this and some recommendations for part names and numbers? Ideal would be a motor with 5/8 keyed shaft to reuse the old multi-step pulley. Pulleys are cheap so that is not a big problem. Anubody have any luck with using a variable speed pulley on a fixed speed motor? What about the DC motors and a VFD? Also if this works good. I would like to upgrade my Drill Press.
Thanks In advance! Charles
 

Ulma Doctor

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#2

JimDawson

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#3
Let me help you out a bit here.

DC motors will not run on a VFD. DC motor controllers are for brushed DC motors.

VFDs operate 3 phase motors only. Before I get flamed here I know there are special exceptions. :eek:

While the HF motor is in fact brushless, it is just a standard single phase squirrel cage motor. Can not be operated on a VFD

I would choose a 3 phase motor and VFD over a variable speed pulley system. You can run many VFDs on single phase.

Another option would be a treadmill motor and controller. Those are brushed DC motors.

EDIT: What Mike said above :)
 

Ulma Doctor

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#4
Treadmill motors and MC60 motor controllers are a secondary means of accomplishing variable speed.
there will be a lot of modifying/making pulleys and/ mounting issues, unless you get a 56 frame DC motor
 

Hawkeye

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What Mike means by modifying is that treadmill motors are generally of much higher RPM that induction single-phase motors. Hense the pulley mods. They do work well and are cheaply available, but you tend to pay in sweat equity.
 

mksj

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#6
You are limited by the motor frame size and shaft to something like a 3/4hp 3 phase motor. I would look into a motor/VFD combo as ther are some savings. Look at DealersElectric. The Teco L510 is decent for this application and simple to setup. A 1Hp motor is the next motor frame size. You should get better low speed control with the newer VFDs that run sensorless vector. You still may want to change to motor pulley size, so you can over speed the motor, typically 90Hz for this type of motor. Treadmill motor is an option, but matching up mounting, shaft size and getting the speed control working may be a bit more challenging.
https://dealerselectric.com/Package-P56X4109-and-L510-101-H1-U.asp
 

Chewy

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Finally got time to respond. Have been researching the information. I bought the Reliance motor in the link from Ulma Doctor. Thanks. Bought a different VFD from model suggested only because more of the one I bought have been sold. Couldn't find any negative reviews. Going to start looking around for more 3 phase motors, for drill press. Bad thing is, a couple of years ago I gave them away because I had no need for them. Just things I collected in trading. If I don't find any soon, I will go with Teco package. Just trying to save money.
2 followup questions. The VFD says it can be controlled by external voltage source for 8 speeds. Has anybody rigged that up? It would be nice to give wife chart saying #1 is ##RPM, etc.
Does anybody have a solution, store bought or home-brew to install a tach on the lathe shaft. I can read it with a reflective tach setup that I used withe engines and pumps. It is a one time deal. I can always make a chart showing VFD percentage equals ##RPM, but it would be nicer with direct readout. Ditto for the drill press.
I'm starting to get spoiled with variable speed motors with readouts and DRO'S. Thanks to everyone for their assistance Charles
 

mksj

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#8
No real reason to use stepped speeds when you have a speed pot. The simplest approach is to use a 0-100 scale on the speed pot and then you can scale that off of the top speed for each range. But even easier is to buy a cheap tach for around $20 and mount it in a small box. Mount a single magnet to the lathe shaft and mount the pickup. Get a small wall wart or modular power supply to run the tach, and possibly a 12V LED light. Put the speed pot in the tach housing.
https://www.ebay.com/itm/Digital-Re...Hall-Proximity-Switch-Sensor-NPN/171385171075

Lathe Tachometer sensor mount.jpg
Mactach Display - 1590B Hammond enclosure.jpg
 

Chewy

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Thank You! Thank You! On the way. I looked around on Amazon & Ebay but couldn't find a full kit setup like this to install.
 

Hawkeye

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You can get project boxes at various places like Radio Shack or electronics suppliers. Just need to drill a few holes and cut the opening for the display.
 

Chewy

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Follow Up. I got the Reliance motor (3/4 hp) and Ebay VFD. Everything worked on the test bench. Then the fun begins. I hooked it up to the lathe and it wouldn't turn an empty Head-stock spindle. I had to start fiddling withe the VFD parameters. Found out that the motor will only go up to 70 HZ. After that it slows down and stops going up to the 400 HZ. that the VFD produces. Had to increase the torque settings from 0. At one point the motor was running hot no matter what the settings or speeds. After two hours I got what I wanted and the setup works beautifully. 2 second start-up gives a slow gentle start. Control is locked to prevent reverse rotation. That keeps the chuck from spinning off the spindle. Motor stays at room temp no matter speed or load. My wife is in love with it. High speed turning down to low speed sanding almost instantly.
I am on the look out for another motor and will duplicate the setup on an old Delta school drill-press. It currently uses two belts and a movable pulley to change speeds. It's about 40 years old and still going strong.

I have potentiometers and switches on order from DigiKey to install on original control panel. I need to remote the VFD to keep it away from dust. Around $160-170 total cost which is not too bad considering what a decent 1/2 hp single speed motor costs. I haven't figured out how to install the tachometer pickup. There is no place to mount the magnet. I may have to make something to attach to the outer pulley.

Thank you to all who contributed. A successful conclusion!! Charles
 

warrjon

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#12
Did you enter the motors RPM and Hz into the VFD, the VFD used these parameters to set the speed curve
 
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