Issues with my two speed motor

[yellow_cad]

I've got an 8X18 Jet lathe with mill head made in the 1980s. The lathe uses a single phase 110 volt two speed motor that uses a capacitor to help it start under load. The electrical switch is mechanical and obviously has a forward button and a reverse button. It also has a button (longer than the f/r buttons so pushing more mechanical levers down) when pushed with either the forward or reverse button that drastically changes the geared speed (sort of like half). Here is my issue: when only pushing, say, the forward button, I get the series of geared speeds that are listed as those coming from the low speed portion of the motor. When I push the forward button along with the speed altering button, I go to about half of the lower range but pretty soon, I see smoke coming from, I believe, my motor. Does this indicate that my two speed motor has lost its high speed range? I don't want to get in a hurry to pull it out to have it rewound, if I'm just missing something. Thanks for any input. Jim

 

[jumps4]

i know nothing about your lathe but if you can see smoke coming out of the motor and everything else moves freely i would say the motor is bad.
can you remove a cover and see the motor?
steve

 

[yellow_cad]

Thanks for the reply. The motor is not easy to get to, plus it only smokes if I try to use the speed range change button. Otherwise the motor runs just fine in one speed range. I was hoping someone would respond that is somewhat familiar with my type of switch.

 

[jumps4]

ya i dont know your machine but the motor is under it's most load in hi range.
steve

 

[pdentrem]

Just some random ideas here.

Does the motor tag or manual show the rpm of the motor in low and high? Like 1725 and 3450 or something of the like?
Maybe there are 2 sets of running coils 1 set for 1 speed and both sets used for the other speed.
I believe that the 3450 rpm motor uses only 1 set(1 pair) and the 1725 uses 2 sets (2 pairs). Or is it the other way around.

Maybe a starting coil is being engaged and it is heating up?
Starting cap or starting coil involved if the motor does not get to speed properly, or there is too much drag and the motor never gets up there.

 

[Alan Douglas]

Where I work, we have a somewhat larger and slightly newer Jet lathe, and I remember helping fix a controller problem a few years ago. But that has a lever in front of the bed, no pushbuttons, and only one speed.

The usual motor would have a set of 4-pole and 8-pole windings, and no connection between them. It might start as a 4-pole in both cases. There's no telling what scheme Jet might have used, and if a motor-rewinding shop had to figure it out, you won't want to pay the bill (I used to rewind motors in a small shop).

Unless you can find an owner who knows, or Jet can tell you, I'd say you're stuck with a single-range motor.