Help Wiring Vintage Century 1.5hp 7-lead single phase motor

[steamandsteel]

Hopefully this is in the right sub-forum.

Quite simply, I'm trying to figure out the wiring on an old Century motor, so I can reverse the rotation.

The nameplate is present, but wiring plate is missing.
It has an external "Capacitor Motor Control Unit", which is matched (serial #'s) to the motor, so not a retrofit.
It does not have brushes, or a centrifugal switch inside the motor.
Motor nameplate claims to be dual voltage, 110/220, has been running off 220 for years.

It is being used on a lathe, with an Allen-Bradley drum switch, but it only spins clockwise (looking at shaft) regardless of the forward/reverse drum switch position.

Here's what I've traced out so far.

Two hot wires come into the switch, with the white hot on terminal 12, and the black hot on terminal 3 with a jumper to 7.
In the off position, the black hot is connected to terminal 4 on the switch, which leads to T1 on the motor.

In the forward position, the black hot goes to switch terminals 1, 4, and 6. These correlate to T4, T1, with the third going in to the control unit on a black wire.
The white hot goes to switch terminal 10, which correlates to T3

In the reverse position, the black hot goes to switch terminals 2, 4, and 5, which correlate to T2, T1, with the third going in to the control unit on a white wire.
The white hot goes to switch terminal 10, which correlates to T3

On the output side of the control unit, the white wire goes to T7, and black wire goes to both T5 and T6 which are tied together.

When I throw the switch in the forward position, the motor turns clockwise without issue. I measured across the capacitor and didn't get more than 14vac with the motor running.
When I throw the switch in the reverse position, the motor also turns clockwise, but sounds as if it is under load/strain, and turns very slowly. I measured around 121vac across the capacitor while it was running.

I've attached some pictures below that should help to get a better idea of the pieces.

 

[JST]

That motor apparently uses a "potential" relay to operate the start. There are two of them in there, and I am absolutely not clear on how they are wired in your motor. So no help

The idea of the relay is to cut out the capacitor after the motor has come up to speed. It is an alternative to the centrifugal switch.

 

[steamandsteel]

That motor apparently uses a "potential" relay to operate the start. There are two of them in there, and I am absolutely not clear on how they are wired in your motor. So no help

The idea of the relay is to cut out the capacitor after the motor has come up to speed. It is an alternative to the centrifugal switch.

Interesting. Thank you. I did notice the capacitor was rated for a certain number of starts per hour, so that would make sense.

There are two wires going into the control unit, and two wires coming out of it. In forward / reverse, only one of the wires (white or black) going into the control unit is tied to hot.

Within a junction box on the control unit, there are a number of wires with stamped brass rings which bear numbers. I can try and investigate that further if it's warranted. Let me know if this could help, or if it's just a waste of time.

In my hours of research, I found someone mention that occasionally a drum switch will be used like a car ignition on these old motors, where you engage the start capacitor/windings and start it in one position before switching to the "run" position.

 

[JST]

That start and run deal is not the best idea, overall.

 

[steamandsteel]

I agree. Easy to smoke the control unit I'd imagine.

Any ideas if there was a standard to motor wiring of this vintage? I can handle retrofitting/upgrading capacitors and that control unit, but I have no idea where to begin with the motor leads and which pairs to test/measure between.

 

[deltap]

Reduce what you see in your pictures to something like this. Then you can make sense of it. You have all those motor leads so disconnect all leads and ohm them out to find which pairs are windings. Your motor is dual voltage so on low voltage four wires will make one winding. Start winding resistance will be much higher than run run winding resistance. The highest resistance will be start and run in series. To reverse the motor rotation reverse the polarity on the start winding. The drum switch is more than likely wired wrong and should be treated as a separate issue after you have the motor running how you want it. I found all this information on the internet in just a few minutes. Educate yourself. It is difficult for someone to look at your pics and tell you how to wire it.