Reversing a 1955 A. O. Smith 3/4 HP Motor

Culprit · Post by **Culprit** » Tue Jan 10, 2012 9:55 am

Here's my plan for adding a reversing capability to my 1955 A. O. Smith 3/4 HP motor.

Many of you have helped me out with advice up to this point - thank you. Much of what I have found searching the forum pertained to other makes of motors with 3 wires going to a motor that uses a start relay. My motor has 2 wires going to it, and uses a centrifugal switch vice a relay. Consequently, this is the plan I have come up with. The principles are the same, the schematic is slightly different.

This plan only calls for disturbing/cutting one existing splice/junction. I like that - less chance for me to short windings. Also in my favor is the fact that I can visually tell the difference between the run and start windings by the gauge of the wire in the coils. That way I don't have to disconnect the coils and check them with a multi-meter to figure out what is what.

Please take a look and let me know if I got my wires crossed somewhere. And I apologize for my handwriting - it was quicker than doing the drawing and annotations on the computer.

And here's the switch I'm going to use:

JPG · Post by **JPG** » Tue Jan 10, 2012 10:36 am

Culprit wrote:Here's my plan for adding a reversing capability to my 1955 A. O. Smith 3/4 HP motor.

Many of you have helped me out with advice up to this point - thank you. Much of what I have found searching the forum pertained to other makes of motors with 3 wires going to a motor that uses a start relay. My motor has 2 wires going to it, and uses a centrifugal switch vice a relay. Consequently, this is the plan I have come up with. The principles are the same, the schematic is slightly different.

This plan only calls for disturbing/cutting one existing splice/junction. I like that - less chance for me to short windings. Also in my favor is the fact that I can visually tell the difference between the run and start windings by the gauge of the wire in the coils. That way I don't have to disconnect the coils and check them with a multi-meter to figure out what is what.

Please take a look and let me know if I got my wires crossed somewhere. And I apologize for my handwriting - it was quicker than doing the drawing and annotations on the computer.

And here's the switch I'm going to use:

Looks good to me!;)

I hope the innards of my 1963 A. O. Smith 1 1/8HP is the same when I refurb it! I plan to replace all insulated wires(badly chafing etc). If so, reversing will be on the agenda.

Culprit · Post by **Culprit** » Wed Jan 18, 2012 10:40 pm

I got the motor re-wired, the reverse switch installed in the headstock, and a new power cord attached. Next up are the bearings then I can put it back together and see how I did.

As I started gingerly picking at the one splice/junction that I had to disturb to re-wire the motor, I noticed a convention that made life much easier - and much less risky. As it turns out, I didn't even have to unwrap that splice. As I studied the motor and visually re-traced everything while comparing it to the schematic, I noticed that the ends of each coil (both start and run) were sheathed in insulation where they depart the coil and head off to wherever they need to be connected. Furthermore, the ends of the run coils (4 ends, two on each of two coils) were sheathed in black, and the 2 ends of the single start coil were sheathed in white. That meant that I could identify which wire going into that splice needed to be cut out without actually opening up the splice or even removing any of the tape from around it.

Culprit · Post by **Culprit** » Sun Mar 11, 2012 2:54 pm

I installed the new bearings in the motor yesterday, put everything back together, and she runs great and smooth - both forward and backward!

cranehead · Post by **cranehead** » Mon Mar 12, 2012 11:50 pm

Being very much a beginner I am wondering what the reversing feature is used for. I am about to go through one of these motors. Does it make sense to add a reverse switch while I'm at it?

TC

JPG · Post by **JPG** » Tue Mar 13, 2012 1:41 am

cranehead wrote:Being very much a beginner I am wondering what the reversing feature is used for. I am about to go through one of these motors. Does it make sense to add a reverse switch while I'm at it?

TC

Unless you know of a specific reason for your needs, probably not.

Lathe junkies like to be able to reverse rotation when sanding so as to clip off wood fibers laying down.

Reversing allows running the strip sander mounted at the rear shaft for simultaneously sharpening lathe tools with the attachment.

There are times when reverse rotation will permit alternate setups, but those are fairly rare.

Only you can determine the answer.

Culprit · Post by **Culprit** » Tue Mar 13, 2012 4:19 pm

JPG40504 wrote: Lathe junkies like to be able to reverse rotation when sanding so as to clip off wood fibers laying down.

That's my main reason. I would also like to be able to flip my 500 Mk 5 to drillpress mode, slip on an extra table carriage and have an under table routing capability. I know the speed isn't optimal, but it does give me more options.

JPG · Post by **JPG** » Tue Mar 13, 2012 6:22 pm

Culprit wrote:That's my main reason. I would also like to be able to flip my 500 Mk 5 to drillpress mode, slip on an extra table carriage and have an under table routing capability. I know the speed isn't optimal, but it does give me more options.

Then it appears the answer is 'yes'.

bdeweese · Post by **bdeweese** » Tue Mar 13, 2012 8:33 pm

As I understand this, it also allows those who wish to convert a 2nd or 3rd machine into a "mini" or "shorty" to run various SPT's from the right side of the unit - instead of being limited to just the left side. This has been my main reason for looking into this as I'm in the process of refurbing a 2nd machine I picked up and converting it to a "shorty".

Bottom line: Reverse = even more flexibility for an already very flexible machine.

Bob