In part one, I discussed removing the pulley from the motor shaft, opening the case, removing the bearings, and selecting new bearings for the restoration. In part two, I will discuss the disassembly, wiring, and cleanup tasks. In an upcoming post, I’ll finish up with the rewiring and restoration of the motor.
Craftsman 115.6962 1/2-HP Capacitor Start Electric Motor – Diagram. Source: VintageMachinery.org
Continuing from part one, I had loosened the end frames and pulled the rotor assembly out through the right side / fan side of the stator. This left the right side frame completely disconnected, but before I could remove the left side / terminal side end frame, I had to get in there and disconnect the machine screws holding the overload protection assembly/thermostat, centrifugal switch, and terminal block from the end frame.
Oh, did I mention that a family of dirt daubers had set up shop inside the motor at some point in the last 65 years? Dirt daubers, if you’re not familiar with them, are more-or-less non-stinging solitary wasps that build mud tubes that harden into incubation chambers for their larvae. They’re pretty cool, but not when they are nesting in your motor.
The wiring exiting the stator was extra crispy after 65 years, so it was important that I be very gentle with it, and avoid moving it more than necessary. A broken wire in the windings would essentially be impossible for me to replace or repair, so the motor would be junked if that happened.
So, I carefully chipped away at the dauber nest, and unscrewed everything I could get at, eventually removing the left end frame.
So what you’re looking at above is the terminal block on the left. That’s a little brown board with two terminal posts that are used to join wires that control the direction of rotation. In the center, you see the centrifugal switch, which opens and shuts based on motor speed, including or removing the start capacitor in the motor circuit. Then on the left, the red button is the overload protector assembly, that resets the motor if it overheats. You can see that the daubers left an awful mess.
I gave it a preliminary cleaning with a toothbrush. You really can’t be too gentle with these old motors.
The wiring, as I mentioned, was crispy and in pretty rough shape. I had to salvage the ends coming out of the riveted windings, since I couldn’t get in there to remove the end of the wire.
Let’s start with my wiring diagram. I’m not an electrician, but I think this gets the points across.
So we have a two-wire power cord coming in the back of the bottom frame to the underside of the motor (passing through a grommet and with a metal cord retainer). The original cord was in rough shape. It also lacked a ground, because grounds were for cowards in 1953, apparently.
I had removed a flat electrolytic capacitor that was mounted under a plate beneath the motor in order to access this lower bay. The capacitor was still kind of working, but I planned to replace it due to its age. It’s not currently shown, but it had two yellow wires going to the capacitor: one from the windings, and one from the centrifugal switch. The rusty bolt head is one of two 3/8″-16 x 5/8″ hex bolts that attach the stator assembly to the lower frame.
I may as well talk here about replacing the start capacitor. The start capacitor goes into circuit during the first few seconds of motor operation, bringing it up to speed. Then, at about 80% speed, the centrifugal switch opens and the capacitor is removed from the circuit. When the motor is switched off and slows down, you hear a clatter from inside the motor, which is the centrifugal switch closing again (it’s normal). The old style capacitors were flat, about 3 in. by 5 in. by bout 0.5 in. thick (book-shaped) and they are no longer manufactured in that form factor. I am replacing mine with a 130 – 156 MFD x 110 / 125 VAC start capacitor # 092A130B125AC1A (made in the USA by BMI) that I sourced from Amazon. It’s a cylindrical-style capacitor that is 1-7/16 in. diameter and about 3 in. tall. The original capacitor was a 124-155 MFD x 125 VAC x 60 cycle start capacitor, so the new capacitor closely matches those specs. You don’t want to go outside the MFD rating by more than 10%, but you can go from, say, a 125 VAC model to a 250 VAC capacitor.
So, back to the end frame wiring. There is a black wire from the power switch to the overload protector assembly, and a yellow wire from the capacitor to the centrifugal switch. Both pass through the gap between the motor interior and the lower frame.
A green wire and a yellow wire exit the windings and go to the terminal post marked ‘2’. A red wire goes from the windings to terminal post ‘4’, a yellow wire connects the centrifugal switch to post ‘4’, and a black wire connects the thermostat reset switch to post ‘4’. Swapping the two yellow wires between terminal posts 2 and 4 will reverse the direction of the motor.
Hopefully, the pictures and the wiring diagram make the wiring arrangement clear.
I proceeded to remove the stator assembly from the lower frame, and took the center band off. I had to cut the power cord, which I’d be replacing anyway.
I stuck a couple of Q-tip sticks into the threaded holes in the lower frame and proceeded to media blast it. Then I cleaned it, hung it up, primed, and painted the lower frame.
I repeated these steps with the end frames, the terminal box cover, and the centrifugal switch shield. I’ll hold off on showing the final paint job until later.
Next, I cleaned up the fasteners. Mostly, that involved wire wheeling on one of my Craftsman block grinders.
Well, I originally intended to finish up this post series in two parts, but this post is getting so long, I think I’ll save the electrical rewiring and reassembly for a third post.
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