Original motor from 1986 gone bad? Busy Bee B-244 lathe, speed is all over the place plus big current draw!

[toysareforboys]

I was doing a massive production run today and was running her for about 10 hours straight then it started to do weird things. It dropped from full speed down to 1/3 speed, drew way more current (dimmed the lights in my shed) for a few seconds to a minute and then went back to full speed, did that over and over, didn't seem to make any different noises, no smells. Even at full speed the amount of torque/power was way way down from what it normally is. After I finished a few more parts with it running like this (about 10 minutes) it permanently dropped to 1/3 speed or less with almost no torque.

When I went to pull the cover off the back of the motor I noticed the air intake screen was plugged up with delrin shavings, so I might have overheated it. I let it sit for a few hours then fired it up again but only 1/3 speed or less, lots of current draw, no torque. I couldn't get the motor cover off because one of the screws to the cover is on the very bottom and I'll have to unbolt the lathe from the bench to get at it. A project for tomorrow maybe.

If I rotate the chuck by hand I can hear some scratching noises in the motor, it was always silent before, but the chuck/motor rotates easily by hand.

Any suggestions on what to look at/for?

If the motor is cooked I'd like to put a motor on it that I can control the speed of (i.e. run it slow but still have full torque). Currently I only have 120v/60hz/20amp available in my shed but I could run 240v to it if necessary. No idea where to start with that stuff though (controller/motor), suggestions appreciated and if you need more info/measurements from the lathe just let me know.

Luckily I was able to finish the production run I was doing so it's not a panic that it get fixed quick.

Thank you for any help you can provide.

-Jamie M.

 

[John O]

A few years ago I went to Carson electric on Milner ave for help with my motor kicking out the vfd.
The person was very helpful explaining my problem in basic language got me to rewire differently.
Did not need parts and didn't charge for the 20 minutes of his time.

 

[toysareforboys]

A few years ago I went to Carson electric on Milner ave for help with my motor kicking out the vfd.
The person was very helpful explaining my problem in basic language got me to rewire differently.
Did not need parts and didn't charge for the 20 minutes of his time.

That'd be a short trip for me. I'll bring it to them and see what they say. Thanks!

-Jamie M.

 

[toysareforboys]

Dropped off the entire lathe to them today. They'll give me a quote on repairing the motor as well as upgrading the lathe to a VFD! Oh baby, can't wait

-Jamie M.

 

[toysareforboys]

Carson couldn't come up with any motors that would fit (that'd work with a VFD) so I picked up the lathe from them unrepaired to come up with some better motor options myself.

I removed the main drive pulley from the lathe chuck driveshaft and the diameter of the shaft is 30mm or just a hair smaller (0.0064") than 1 3/16" so I ordered a split pulley bushing from McMaster Carr in 1 3/16" size (split pulley bushings compress to squeeze the full circumference of the shaft when you bolt a pulley on them) and it fits like a glove, nice!

For a motor I chose a monster stepper motor. I know, I know, stepper is not the the best choice for "high speed" lathe operation because the power/torque massively drops off at high RPM but I just love stepper motors, how simple they are to control (both speed and direction) as well as how much torque they put out (especially at slow speeds).

I went with a massive NEMA 52 sized closed loop stepper motor with a peak holding torque of 28NM, peak pull-out torque (i.e. torque it produces while spinning) of 25NM and at the maximum speed I'll be running it at (1000rpm motor, 2000rpm chuck) it'll provide 6.25NM at the chuck (12.5NM at the motor). The stepper driver it comes with is also super nice! Single phase AC 120v or 240v and it'll spit out 3 phase at up to 8 amps/2000 watts. Closed loop stepper motors (and drivers) can be pushed at much higher speeds without losing as much torque as open loop steppers and closed loop also have the benefit of much much better efficiency so the motor doesn't heat up as much.

It has a digital readout display (of RPM, steps, current/watts, programming options, etc) and you can put it in "speed hold" mode, so say you set it at 500rpm, if you start to machine something and it starts to slow down the motor it'll keep putting more and more power into the motor to keep it at the exactly same RPM! It can even way over current it for a short duration, sweet : https://www.aliexpress.com/item/33018809499.html (obviously with only 120v/15 amps available to me at the moment I'll have to limit the maximum current to the motor, easy with just one setting)

To bolt it to the lathe I picked up a NEMA 52 L/90 degree mount from the same supplier: https://www.aliexpress.com/item/32770775579.html (I'll make an adapter plate to convert the bolt pattern of the stock motor to NEMA 52)

For a speed/direction controller there are quite a few options:

The first/easiest/cheapest option is a cheap stepper controller from Ebay/Amazon/Aliexpress, i.e. from cheapest to "most expensive":

a) $6.59 CAD shipped (free Amazon Prime next day delivery), 8-24v DC input, nice digital display shows duty cycle percentage (0% to 100%), maximum frequency output of ??? : https://www.amazon.ca/dp/B07WMN8255/

b) $7.89 CAD shipped (free Amazon Prime next day delivery), 8-24v DC input, has high/medium/low range settings for the speed control knob, maximum frequency output of 160khz: https://www.amazon.ca/dp/B07WMN8255/

c) $11.99 CAD shipped (free Amazon Prime next day delivery), 5-12v DC input or 15-160v DC input (WARNING: If using more than 5v on the 5v to 12v input jack you must make sure your stepper motor driver can accept 12v pulse signals or you'll have to use a resistor!), has high/medium/low range settings for the speed control knob, maximum frequency output of 127khz: https://www.amazon.ca/dp/B07WT39T4S/

All three options have enable/disable button (starts and stops the motor INSTANTLY, without soft start/stop adjustability unless your stepper driver has it built in), reverse direction button (don't accidentally press this when running at high speed, hopefully my driver has protection against that) and of course speed control knob (with the latter two options having an adjustable range for the knob).

I went with option c as there were a lot of demo videos and wiring diagrams online for it and you can change one of the parts in it to adjust the frequency range it puts out to tune the speed knob for the perfect setup (i.e. 1000rpm motor rpm/2000rpm chuck RPM at knob 100% and super slow 100rpm motor/200rpm chuck rpm for threading at 1% knob). I ordered a cheap $13 CDN 24v DC power adapter to power the controller: https://www.amazon.ca/gp/product/B083ZT4H5N/

Another neat option I saw for remote RPM display (as well as speed control and a ton of other stuff like soft start, etc.) was this $10 remote programmer for the driver so I ordered it as well: https://www.aliexpress.com/item/4000107828403.html

All of the parts have arrived so far minus the ones from China, motor, driver and remote driver programmer/display:

The big pulley (40 teeth) is for the stepper motor (15/16" shaft) and the small pulley (20 teeth) is for the chuck driveshaft (1 3/16" for 30mm shaft). I got a few belts in different lengths and there is also an adjustable tensioner pulley already on the lathe so I should be able to make one fit.

Hopefully people are alive at the factories in China, no replies to e-mails/my orders so far!

Now I wait on the slow (fedex express) airplane from China!

-Jamie M.

 

[toysareforboys]

First part arrived from china, woot!

That arrived by DHL, 4 days from China to Canada, not bad!

I got a notice from Fedex about the motor and drive though, that they are short staffed due to corona virus and special decomanition has to be done to every package. Still no tracking number so might be quite a delay

-Jamie M.

 

[toysareforboys]

Big shipment from China today!!! The motor, motor controller, mount and motor temperature/power consumption display!

The live RPM display arrived as well (not in above pic).

I have everything I need to build it now, just need some time, have a pretty absurd work this week

-Jamie M.

 

[toysareforboys]

Oh, and I completely forgot! I'm getting 240v 100amp service installed in my shed on Thursday! So nice to have 240v, now I can get a nice welder and plasma cutter

-Jamie M.

 

[toysareforboys]

Electrical upgrade is complete! Took forever because of this Covid-19 stuff

Now I gotta work on mounting the new motor to the lathe... wish me luck!

-Jamie M.

 

[toysareforboys]

Absolutely absurd! The stock motor mount studs fit the new stepper mount perfectly!! So lucky

Looks like the idler pulley/pulley cover door mount plate needs a bit of a trim

All trimmed, fits nice now!

Now for a test fit of the motor...

OMG, SHE FITS! Nice.

I put the pulleys on and bolted them up, but didn't know you can only do that once, without a pulley puller (because of the split bushing), so they didn't get aligned good at all I'll rent a pulley puller tomorrow and get them off so I can do a nice alignment.

Slow speed demo video (I'll post a high speed one once I get the pulleys aligned):

-Jamie M.