Modern polyurethane belts give loads of grip (get a set from Doug Feistamel), so you don't need toothed belts.The desire for toothed belts comes from one of the older books where the author goes to great lengths to make his own toothed pulleys. The complication and resulting noisy drive are just not worth it.

Yes, it is still a good idea to keep the stepped pulleys. Using the pulleys to reduce the speed range gives you higher torque at lower speeds, which is usually a good thing - theoretically ideal. It also allows much finer control at lower speeds. I found I rarely used the speed controller. Changing speeds with the belts was all I needed for most jobs especially with the extra low speed pulley. On my Unimat 3, which only has four speeds on the belts, I may use the speed controller more, but I may also make some more pulleys for more flexibility. I think it is possible to build a back gear into the large pulley, but it will not be simple.

I suggest that when you change the motor, you do not change anything else until you have got used to the lathe again. Then see what might help.

*Keith,
*I did a search on EBay for Unimat belts Doug Feistamel and it did not
return anything useful. Do you by chance know the Seller’s Web address?
Dick

"On my power box I have two sockets for the motor - one direct from the 24 V, the other from the speed controller. The direct one has a forward/reverse switch, but not the speed controlled connector. Reversing the power while the motor is still spinning is a good way to blow up the speed controller."

Yes, not a good idea to reverse unless completely stopped. Also on a lathe with a threaded on chuck you have to be careful using reverse. I used the color coded wires, Red +, Black - and just added individual wire push connectors. So if needed , I could just unhook and reverse the wires to reverse the motor, Something that I have yet needed to do.

?Jeff

-----Original Message-----
From: Keith S. Angus <keithsangus@...>
To: Jkle379184 <jkle379184@...>; [email protected]
Sent: Sat, Sep 25, 2021 5:23 am
Subject: Re: [Unimat] Sewing Machine Motor w/foot pedal?

On Fri, Sep 24, 2021 at 03:06 PM, Jkle379184 wrote:

?I seem to recall that the power supplies were commonly used to power LED lighting. Here is a photo of the Motor that I used, the box that I put the controls in and a crude wiring schematic. I added switch position to bypass the sped control to run full speed.

The power supplies are often quoted as being suitable for LEDs, but you'd need a lot of LEDs to justify 24V at 10A! Really they are general purpose power supplies - use them for whatever you like.

The speed control you are using is one of the ones I suggested for Oldtoolmaker.

On my power box I have two sockets for the motor - one direct from the 24 V, the other from the speed controller. The direct one has a forward/reverse switch, but not the speed controlled connector. Reversing the power while the motor is still spinning is a good way to blow up the speed controller.

>>Measured full output speed of this motor was 3431 RPM. I drilled out the pulley to 8mm and it fit the motor shaft perfectly.

The higher power motors run a bit slower than the lower power ones. I got a little over 4000 rpm from my 130 W motor. Somewhere or other this is documented by the motor suppliers. As said before, I got about 6000 rpm at the chuck at the highest speed setting on the pulleys.

If my motor had had the longer shaft I would have opened up the pulley. Since the shaft was too short I made an extension at 6 mm and left the pulley alone. I arranged to drive it by pins, more or less as in the original, and held it on with an M4 screw, as per the original.

>>Some photos of the motor end plate mods and the "top Hat" for the mounting screw all done on the Unimat.

You have the motor with the brushes at the back. This makes it easy to add the extra fixing hole to the front plate without worrying about screws getting mixed up with the wiring. Note that to modify the plain front pate it is not necessary to dismantle the motor completely - it is simpler to just take the front plate off.That way you don't have to disturb the brushes, and fight the magnets when getting the armature out, and in again. If the brushes are at the front then it needs a bit of thought how to modify it without shorting out the electrics. That's one reason why I used an adaptor plate and left the motor alone.

The Unimat motor has two M5 screws at 42 mm spacing. The DC motor has three M5 holes on a 42 mm circle, so you only need to add one M5 hole to fit the DC motor to the Unimat bracket. You might get away with tapping it straight into the motor end plate, but adding this reinforcement is a good idea.

I had a big BANG lock-up on my SL, and after that the motor bearings were shot. If you take the motor apart consider replacing the bearings with good quality ones (SKF, NSK, FAG, etc.) while you have the chance. At least measure them up so you know what size may be needed in future. I've forgotten what they were, but it wasn't hard to find replacements.

>>Photos of the motor taken apart, easy to do, just two long screws. Put the end plate with the brushes over the armature shaft first and then put that into the stator tube when putting it back together. The modified end plate with the top hat epoxy glued in place, drilled out and test mounted to the Unimat bracket.? And the last one is the unit up and running. Notice the drive belt. Just a plain old Buna white O ring, they are cheap and work great. ?I drilled the pulley out to 8mm to fit the shaft. Then I drilled the pulley for a small set screw to fit the flat section of the armature shaft. All work was done on one of my Unimats. You could do this first and then when done replace the Unimat motor with the 24vdc motor when done.
Jeff

Mainly covered in comments above. If you take the motor fully apart mark the end cover positions with a dab of paint or similar. It helps to get the screws back through if the covers are properly aligned. If I was doing it again I would also file a small point on the long screws, as that would help to get them into the tapped holes in the end cover.

In general, if I had this motor to work with, I would have done the job very much the same way. As it was, the motor I had was significantly different, so I did things differently. If you can get a motor like this one (regardless of power) with the brushes at the back end and with a long shaft, it will be simpler. I would still recommend the 130 W motor, as it gives a bit more space around the working area, and it goes a little faster, but these are not the most important things. I haven't seen many motors with the longer shaft. I reckon it would be worth spending some time searching for that, and the brushes at the back end,

The wiring can be even simpler than shown. I think the direct power option is good, but I couldn't tell you why. My power box was more complicated as it allows for a range of possible, but unknown, other uses. The biggest problem, in my experience of such things, is finding a good size box for everything. I still favour a wooden base under the lathe with the electrics inside, but that means you have to build it, so it depends on your woodworking skills. I used a commercial equipment box, but, along with the 24 V PSU that probably cost more than the motor and speed control combined. Fortunately someone in industry owed me some money/a favour, so I didn't feel the cost!