Craftsman 101 / Atlas 618 Lathe Project: DC Variable Speed Motor

[MDof2]

I've searched around the forum, and obviously, I'm a lurker in most of my time here, so I'm reaching out for help on where to find some info. If any of you old timer Hobby-Machinist forum veterans could point me in the right direction, I'd be most appreciative.

I've got a couple treadmills I'm planning to use as donor parts for a few projects, one being a variable speed motor in my 618 lathe. In some googling around I've read a few different sites / youtube, etc. with various information. I searched around Hobby Machinist and the forum / site is simply massive so didn't know exactly where to start. Electrical subforum, Atlas / Craftsman / Other? Is there a known / popular thread or sticky that touches on the topic for those who are starting down this project?

I understand the basics, electrics, have the motors, will use the treadmills as donors, particularly in this case, the DC motor, and the PWM controller, or worse case, buy one from an online source. Need to sort out some pulleys once I get looking at the motors on the bench, RPM measurement, box for controller, a little fabrication for mounting, etc.

Any tips, pointers, reference threads, etc.?

 

[wrat]

If you have all the parts and the circuits work fine, then you're in good shape.

A big oops is getting it all built and it won't run. So make sure it runs first.

 

[mattthemuppet2]

here's mine.

Atlas 618 Treadmill Motor Install

Hi all, this is a summary of my recent project to install a treadmill motor on my Atlas 618 (see http://www.hobby-machinist.com/threads/wiring-up-a-treadmill-motor-i-know-i-know.37159/ for the full experience!). It got a bit lost in that thread and Nels thought it would be worth posting it here...

www.hobby-machinist.com

I've since replaced the motor with one that has a separate fan and flywheel and replaced all the pulleys with polyV pulleys (motor, countershaft, countershaft step pulley, spindle step pulley) as they have better grip at a smaller diameter than regular V pulleys. Just the motor and countershaft pulleys alone would be worth doing, you can even reuse the ones from the treadmill.

I've done installs on my lathe, drill press and mill, and I'll soon be doing one for my new lathe, so fire away with any questions and I'd be happy to help.

Here's the DP install:

Treadmill Motor Conversion On A Walker Turner Drill Press

alright, next project on the list - adding a variable speed treadmill motor and tach to my WT drill press which also doubles as a sort of mill. It currently has a 1/3hp motor with 5 step motor>intermediate>spindle pulleys to give 250-900rpm and 3000-5000rpm. Changing belts in the lower range...

www.hobby-machinist.com

and mill:

Treadmill motor conversion for a Grizzly 6x26 knee mill

I bought this second hand last year and it's awesome (1st proper mill!), but I've been spoilt by the variable speed treadmill motors on my lathe and drill press, so I've been waiting awhile for the opportunity to add a treadmill motor to my mill. The 3 usual challenges are 1. how do I stop the...

www.hobby-machinist.com

 

[markba633csi]

Some folks mention that the original treadmill controller is sometimes awkward to use- for example, speed knob or lever must be set to zero before motor will start, or contains a slow start circuit that must be disabled, etc.
You can use an aftermarket controller like KB electronics instead; they are reasonably priced and reliable. Ebay is a good source. The KBIC-125 is a good model, up to about 1.5 horsepower
-Mark

 

[RJSakowski]

I am currently working on a dc brush motor upgrade for my G0602 lathe. My lathe is about twice the size of yours and I am replacing the 1 hp. induction motor with a 2.25 hp dc brush motor using a pwm controller.

One of my realizations when using a pwm modulation system foe speed control is that feedback from a motor speed sensor was essential. The reason for this is that, while dc. brush motors have good low speed torque at low speeds, the output speed is highly sensitive to load variation. A typical variable speed tool like a power drill uses biofeedback to apply more power to the motor when it starts to bog down so sensitivity to load isn't noticeable.

Unfortunately, my motor was new stock and not salvaged from a treadmill so I had to look elsewhere for a controller. The controller that I chose wa probably intended for constant load applications so, while I am able to dial any speed from 200 to 4,000 rpm, I have to play with the speed control to adjust speed as the load changes. This is less an issue at higher speeds but one of the primary reasons for changing my drive was the ability to operate at lower speed.

The present state of my project is adding a rotary encoder to my driven gearbelt pulley which is run directly off the motor. The encoder will consist of ten neodymium magnets and a Hall effect switch to provide pulses proportional to motor speed. Theo will be used to create an output voltage proportional to motor speed which will be compared to the control voltage and an error signal use to decrease or increase the motor speed.

The bottom line is that when making a conversion to a d.c. brush motor, make sure that the controller is able to compensate for load variation.

 

[mattthemuppet2]

most treadmill motor controllers compensate fairly well for changes in load in open loop mode unless you're really pushing it. The fancier ones use a magnetic pick up off of the roller pulley to work in closed loop mode. On both my MC60 controlled set ups the controller will increase current until it trips the overcurrent protection, though occasionally I can get my lathe to slow down if I'm really pushing it (1/2" drill into hardwood seemed to do it - lots of friction).

For the MC60/65 controllers you can also cut a resistor to remove the "start from zero" function. For others you can use a reversing switch on the motor power wires to do the same, then you only have to "start from zero" once when you turn on the machine (like on my drill press).

 

[markba633csi]

The KB controllers have torque compensation also and can operate closed loop if you can provide a tach input
-M

 

[mattthemuppet2]

yeah, KB controllers are really nice - they're what I'd choose if I had to buy one

 

[MDof2]

here's mine.

Atlas 618 Treadmill Motor Install

Hi all, this is a summary of my recent project to install a treadmill motor on my Atlas 618 (see http://www.hobby-machinist.com/threads/wiring-up-a-treadmill-motor-i-know-i-know.37159/ for the full experience!). It got a bit lost in that thread and Nels thought it would be worth posting it here...

www.hobby-machinist.com

I've since replaced the motor with one that has a separate fan and flywheel and replaced all the pulleys with polyV pulleys (motor, countershaft, countershaft step pulley, spindle step pulley) as they have better grip at a smaller diameter than regular V pulleys. Just the motor and countershaft pulleys alone would be worth doing, you can even reuse the ones from the treadmill.

Perfect. The exact type thread I was looking for to churn the idea engine of input and motivation.

Thanks all for the add'l input and suggestions. Will do some further reading / planning / etc prior to cutting. Learned that lesson too many times.

 

[mattthemuppet2]

you're welcome! treadmill motors are pretty easy to work with. The only issues tend to be with the controllers, depending on which one(s) you have. MC40/60/65 = piece of cake, MC2100 = bit more complicated, bespoke controllers that use push buttons on the control panel = buy a new controller.