Logan 1875 Motor Question

[HiCap239]

Hello Everyone,
I have not been doing much with the newly acquired Logan 1875 due to work constraints. I just started a few interesting mods I will post when finished. While working on one of these mods which are new feet (Hudson bearings I am machining into heavy tubing)...more on this later. I have ran into an interesting issue. The lathe has been running well, I have not used it to much though up to this point. While using it Sunday I thought man this thing is the best thing since sliced bread, as I looked at my Asian 9 x 20 in disgust....Lol a short time later I noticed that when I turn the power on the motor sounded labored and now the chuck looks like it does not know which way to go. The chuck rotates 1/2" back and forth and that is it. If I take my hand and spin the chuck in the direction it needs to travel the chuck will turn. It takes off slowly though and the motor sounds labored while it gets moving, then gets to speed. At regular speed the motor sounds normal. Thinking it was a heat issue I stopped my project and checked the motor, it smelled a bit warm but was not hot. I unplugged the Lathe and reached in and could touch the motor and hold my hand on it so it was not a heat issue. It does not matter if the motor is cool or has run a while. I have checked and it does the same thing in either direction. I have also checked all the pully's & belts for tightness. Everything is smooth as silk and rotates freely and very easily with no binding or over tensioning whatsoever. The motor does this with or without the bull gear engaged. It does not matter what arrangement I run it in with lead screw off or on also. Is the motor on its way out? This issue occurs every time I use the Lathe now. I have went over everything that I know mechanically and I cannot find anything. It looks like the original motor and I am wondering if it is just that it has reached its end of use. Any ideas? If it is the motor does anyone know of a good replacement. I am not overly versed with electronics and I do not know what these came with from the factory. The owner told me it was 110V single phase. That is all I know as far as the motor is concerned. All the wiring inside looks OK also. When the motor gets up to speed and I use the lathe it seems like it is fine, no loss of power when I make a pass across a steel shaft. Any info would be greatly appreciated. Thanks in advance guys.

 

[Bob Korves]

Assuming it is a capacitor start, single phase motor, you probably have a problem with the start capacitor, which have lifetime issues, or with a sticky or poorly contacting centrifugal start switch, which normally engages the capacitor when the motor is stopped and disengages the capacitor as the motor reaches a certain RPM. Both very common issues with capacitor start motors. Those motors are fairly easy to work on yourself, and usually not expensive to have a motor shop look at and repair. We really need to have a sticky on this site explaining the problem, symptoms, and solutions...

 

[HiCap239]

How do I determine if this has a capacitor start? Is the capacitor on the motor, on or in the switch or somewhere in between? Thanks for pointing me in sort sort of a direction with this.

 

[Dave Paine]

Agree with Bob, something in the start circuit is not working. How about posting a picture of the motor. A single phase motor needs a circuit to start the rotation. In modern motors, this is a capacitor which is seen as a "bump" on the side of the motor. The capacitor creates a temporary second phase to get the motor spinning and spinning in the correct direction. This temporary circuit is controlled by a centrifugal switch. Once the switch reaches a certain % of the rate RPM, it opens dropping the capacitor out power. On your Asian lathe you should hear a click when it starts and another click as the motor coasts down when you stop the motor.

Without a start circuit the motor will behave like you mention. It does not move much and may move in either direction. Turning the motor manually gets it to run.

Some older motors have a permanent circuit wired to create the second phase or magnetic field. These will not have a bump on the side since the winding is internal.

 

[wa5cab]

A few early capacitor start motors used a rectangular capacitor mounted in the motor base. But most starting capacitors are cylindrical and mounted under a sheet metal cover on the side or top of the motor.

The motor will have four coils mounted at right angles to each other and called the start winding and the run winding. Several things can happen. The switch can stick either open or closed. If it happens to stick closed, the motor will not run properly after spin starting it. The switch contacts can burn and not make connection. The capacitor can fail either shorted or open. The start winding can fail open. Of these, the most common two are switch stuck open and capacitor open. In both of these cases, the motor will spin start, take longer that it should to get on up to speed. And run OK until you stop and try to restart it. If you aren't at least partially electrically savvy, your safest and quickest bet is to dismount it and take it to an electric motor shop. Either bad capacitor or stuck switch they should be able to fix PDQ.