Doerr AC Motor Rebuild

[damnesia]

I'm rebuilding a Doerr motor, specifically cleaning it up and replacing the two bearings. I have two issues I'm hoping someone can help me with.

1. When pressing the bearing onto collar on the front part of the motor ( first picture ), it doesn't look like the bearing will stop on it's own. Do I eyeball it to press it until it's fully on the collar?


2. The second issue was an accident. This is wired for 115V ( which is want I want ). When I took the back part of the case off, two wires came off their terminals. One goes the starter capacitor and the other goes into the winding. Maybe the wire with the shiny terminal attaches to the shiny terminal on the motor ( in the pictures )? However thinking about it, I think the starting capacitor should be connected to the incoming "hot" wire so the motor can start. Can anyone help me to determine for sure how those wires are supposed to be connected? I'm eventually going to rewire this for 230V so I want to ensure I have things hooked up correctly.

Thanks and let me know what other information I can provide.

 

[6PTsocket]

I'm rebuilding a Doerr motor, specifically cleaning it up and replacing the two bearings. I have two issues I'm hoping someone can help me with.

1. When pressing the bearing onto collar on the front part of the motor ( first picture ), it doesn't look like the bearing will stop on it's own. Do I eyeball it to press it until it's fully on the collar?


2. The second issue was an accident. This is wired for 115V ( which is want I want ). When I took the back part of the case off, two wires came off their terminals. One goes the starter capacitor and the other goes into the winding. Maybe the wire with the shiny terminal attaches to the shiny terminal on the motor ( in the pictures )? However thinking about it, I think the starting capacitor should be connected to the incoming "hot" wire so the motor can start. Can anyone help me to determine for sure how those wires are supposed to be connected? I'm eventually going to rewire this for 230V so I want to ensure I have things hooked up correctly.

Thanks and let me know what other information I can provide.

It may be a run capacitor , not a start capacitor. With the motor as disassembled as yours, you would see the cetrifugal switch if there is one. On the shaft, do you see a switch, weights and springs?. If there is no switch, it is a run capacitor. What is the value of the capacitor? A run capacitor would be probably less than 20ufd. A start capacitor would be more like 470 ufd. In either case, one side of the capacitor would go to one side of the AC line but would not be on the wiring instructions on the motor plate, that I can see in your photo. Did you run your motor model number to see if there is wiring info on line? We just found the wiring info for a Baldor motor. If they are still around, the company is often a good resource for electrical questions and bearing pressing info. Sometimes there is a selective stack of washers to adjust the end play between the bearings

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[damnesia]

It may be a run capacitor , not a start capacitor. With the motor as disassembled as yours, you would see the cetrifugal switch if there is one. On the shaft, do you see a switch, weights and springs?. If there is no switch, it is a run capacitor. What is the value of the capacitor? A run capacitor would be probably less than 20ufd. A start capacitor would be more like 470 ufd. In either case, one side of the capacitor would go to one side of the AC line but would not be on the wiring instructions on the motor plate, that I can see in your photo. Did you run your motor model number to see if there is wiring info on line? We just found the wiring info for a Baldor motor. If they are still around, the company is often a good resource for electrical questions and bearing pressing info. Sometimes there is a selective stack of washers to adjust the end play between the bearings

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There is a centrifugal switch. I'll go out to the shop in a bit and measure the capacitor too. I looked on line for a schematic but couldn't find one ( others have the same issue ). Doerr was sold a couple of times and their new parent is still around, but say they have limited support/diagrams for these old motors. I'm thinking of going out to trial and error it to see where that wire goes. Seems like even if it was hooked up incorrectly and only run for a couple of seconds it wouldn't fry the motor, but I've been wrong before

Thanks for your response.

 

[6PTsocket]

There is a centrifugal switch. I'll go out to the shop in a bit and measure the capacitor too. I looked on line for a schematic but couldn't find one ( others have the same issue ). Doerr was sold a couple of times and their new parent is still around, but say they have limited support/diagrams for these old motors. I'm thinking of going out to trial and error it to see where that wire goes. Seems like even if it was hooked up incorrectly and only run for a couple of seconds it wouldn't fry the motor, but I've been wrong before

Thanks for your response.

In the event that there is a centrfugal switch, the common arrangement is that there are three motor windings. The two identical ones are in series for 240 and in parallel for 120, across the AC The last winding is the start winding. One end of the winding goes to the capacitor and the other end goes to the switch. The other end of the capacitor and switch go to the two sides of the AC line. Flipping one of the run windings end for end, whether in series or parallel, will reverse the motor direction.


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[sselander]

Doerr was sold to Emerson Motor Technologies in 1986.
Emerson Motor Technologies was then sold to Nidec Motor Corporation, a Japanese company, in 2010.
The U.S. address for Nidec is the same as the old Emerson address.
(8050 W Florissant Ave Saint Louis, MO 63136)
U.S. motors is the name Nidec labels their motors in the U.S. after Emerson was sold.

US motors:
http://www.usmotors.com/

Nidec
http://www.nidec-motor.com/

Side note-
Three electric motor companies were founded or co-founded by a Doerr.
Baldor, Doerr , and Leeson
https://www.mrosupply.com/page/baldor-leeson-two-companies-one-origin/

 

[6PTsocket]

Doerr was sold to Emerson Motor Technologies in 1986.
Emerson Motor Technologies was then sold to Nidec Motor Corporation, a Japanese company, in 2010.
The U.S. address for Nidec is the same as the old Emerson address.
(8050 W Florissant Ave Saint Louis, MO 63136)
U.S. motors is the name Nidec labels their motors in the U.S. after Emerson was sold.

US motors:
http://www.usmotors.com/

Nidec
http://www.nidec-motor.com/

Side note-
Three electric motor companies were founded or co-founded by a Doerr.
Baldor, Doerr , and Leeson
https://www.mrosupply.com/page/baldor-leeson-two-companies-one-origin/

Common in other industries, too. The big truck manufacturers Kenworth and Peterbuilt, that's Peter Kenworth.

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[6PTsocket]

Doerr was sold to Emerson Motor Technologies in 1986.
Emerson Motor Technologies was then sold to Nidec Motor Corporation, a Japanese company, in 2010.
The U.S. address for Nidec is the same as the old Emerson address.
(8050 W Florissant Ave Saint Louis, MO 63136)
U.S. motors is the name Nidec labels their motors in the U.S. after Emerson was sold.

US motors:
http://www.usmotors.com/

Nidec
http://www.nidec-motor.com/

Side note-
Three electric motor companies were founded or co-founded by a Doerr.
Baldor, Doerr , and Leeson
https://www.mrosupply.com/page/baldor-leeson-two-companies-one-origin/

Does that mean that Rigid belongs to them ,too. Emerson made Sears and HD shop vacuums, and the plumbing division is well known for quality products. I believe Emerson is also connected or owns the HD Rigid tools.

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[damnesia]

I think I may have figured this out after I cleaned the wires. The unhooked one going to the winding was marked T4 ( this has to mean terminal 4, the one hooked to terminal 1 was marked P1 and the one hooked to terminal 2 was P2 ). The one going to the capacitor was unmarked. The only other unmarked wire was hooked to the centrifugal switch plate. I think it also makes sense that something has to be connected to both sides of the switch . Wiring it like this, when the switch is engaged ( on start up ) there is 0Ω, and when circular motion deactivates the switch I get something like 400 MΩ.

I put the bearings, but I'm a little nervous about giving it a test run :\ I plan on doing it later today (Monday).

 

[6PTsocket]

The wiring diagrams are on your motor. Those T designations are somewhat standard. and are similar from brand to brand. Please don't hold me to this but I seem to recall 1 and 2 are the ends of one run winding and 3 and 4 are the other. They are in parallel across the line for 120 and in series for 240. The start winding is in series,with the capacitor and and the switch across the AC line. The order does not actually matter elecrically, but generally the,winding is in the middle with the cap and switch on either side. As,for the bearing, there should be a minimal amount of end play when it is back together. The shaft should not bind either. If have that, you should be OK

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[damnesia]

It works. Thanks for the input guys.

 

[etherhuffer]

Back from the dead. I have the same motor on an old compressor. It struggles to start and some sparking noted. Are brushes available for older motors? I have yet to pull mine.

 

[dogdog]

That op motor is an ac induction motor, so no brush.

 

[etherhuffer]

OK, so electrical is not my high point but I can get there if I take my time. The motor is trying to start up and barely gets moving, and has tossed the breaker on me as well. Start capacitor maybe? Any info appreciated. Even if you have to write it on a stick and hit me in the head with the stick

 

[marinusdees]

Back from the dead. I have the same motor on an old compressor. It struggles to start and some sparking noted. Are brushes available for older motors? I have yet to pull mine.

If it is sparking, no brushes, has to be the centrifugal (start) switch.

 

[etherhuffer]

Cool. Found these guys online http://www.carbonbrush.com/ They said they may have switches, but no way to reference by model. Need to tear it down and do a measure and compare kind of deal.

 

[dogdog]

Cool. Found these guys online http://www.carbonbrush.com/ They said they may have switches, but no way to reference by model. Need to tear it down and do a measure and compare kind of deal.

Centrifugal switch is mechanical, there are electronic version as well from Korea or China. Usually they can be repaired with a little clean up of the contact points. Plenty of you tube videos on that. I would test the cap as well. And make sure start cap is still within spec. And or some one haven’t over size it for what ever reason. Only way to find out is opening it up, opening it up is pretty easy, just take note of how it was attached by taking some pics, putting it back might be a little confusing if you don’t have pic reference . Still not that difficult. Just be patience .

 

[bubinga]

It works. Thanks for the input guys.

You can kind of see a "witness mark" on the shaft where it's shiny. Then sort of a dirty spot.
Is that what you went by?

 

[etherhuffer]

capacitor tests out bad on uF test on meter. Switch is pretty tired and corroded. Going to order both and replace.

 

[etherhuffer]

So the OEM capacitor is Mallory, 534 uF. Looking online there are lots close to this, and one hard to find that matches spec. Most show a capacitance range. How do I choose? I assume going higher will stress the windings more, going lower will give me less torque

 

[dogdog]

You can have it over size up to 15% so 550uf 560uf and what ever voltage rating minimum.

You can just clean the contacts of that switch with some solvent and some fine sand paper and grease it up with some light coat of dielectric grease. IF the spring tension is still good. Doubt you can still find a centrifugal switch that matches…. Or go electronic. Don’t have experiences in this but there was two of three old threads some one mention they do.

 

[dogdog]

Mallory is just a brand. It is a good brand. Still just a brand so…. You can just match it with capacitance and voltage.

 

[etherhuffer]

Motor shop said 460-530 was as close as they could go. It’s all back together, just need rain to cease so I can mount it up to check it

 

[MBfreak]

Helped a friend with his single phase motor from China, running the hydraulics on a lift.
In Sweden, most everybody has three phase so motors are as simple as can be.
But not this US inspired China import. And the centrifugal switch blew up.
Installed a timer that energized the start winding 0,7 sec at start up. Problem solved

Ola

 

[etherhuffer]

OK failure. all back together but won't start under load, that is to say when tank has pressure. With an empty tan k no problem. Thoughts? Unloader valve?

 

[etherhuffer]

Unloader hisses. Might be a check valve. Oof

 

[etherhuffer]

Question: Do check valves have gaskets on the poppet?

 

[etherhuffer]

resurrecting this old post. I rebuilt all the bad stuff on my compressor, and it works fine. My problem turns out to be voltage drop! The line to my shed is too long, and the motor won't start under load. Not sure if a newer replacement motor would start any better. Any thoughts?

 

[micromind]

If the motor is running on 120 volts and if it can be changed to 240 and 240 is available, this will almost certainly solve the problem.

 

[etherhuffer]

Can't do that . 120V only

 

[seber]

Replace the pressure switch with one that has an unloader valve and unload the plumbing. Now you can start without load.

 

[etherhuffer]

It has an unloader. Problem is my voltage drop. I am just wondering if a newer more efficient motor would fix this issue.

 

[The Cobbler]

a new motor will likely have the same problem ( assuming your motor is good)
what size is it, can you go to a smaller HP motor?

 

[etherhuffer]

a new motor will likely have the same problem ( assuming your motor is good)
what size is it, can you go to a smaller HP motor?

Not sure, might be worth a try. I needed a 20A circuit in the shed to make this work, I only have 15A. Dang.