Brendon_t Posted September 16, 2015 Report Share Posted September 16, 2015 If I had a belt/disk unit, I would just pick up a cheap spindle sander from cl, being that I don't and space is at a premium in my shop, I think the belt/ spindle as more useful than a belt/disk. At least in the Work I do. Quote Link to comment Share on other sites More sharing options...
Janello Posted September 18, 2015 Report Share Posted September 18, 2015 Add me to the list as well. Returned one about 1.5 years ago for motor hum, no problems since. Quote Link to comment Share on other sites More sharing options...
widowmack Posted June 5, 2019 Report Share Posted June 5, 2019 I am having the same problem. It ran good when I first set it up. It had less than 2 hours of run time on it and then it would try to start then hum. Quote Link to comment Share on other sites More sharing options...
Mark J Posted June 5, 2019 Report Share Posted June 5, 2019 In the intervening years since the original post this has continued to be a very popular unit and now has a lot of cloned competition. So it's worth trying to fix. I would suggest contacting Rigid or HD to see what they say. Quote Link to comment Share on other sites More sharing options...
o0dude0o Posted February 10, 2020 Report Share Posted February 10, 2020 (edited) The actual issue is the motor is an induction motor without any rotor magnets involved. The rotor is an aluminum cage type which depends on the force generated by the lorentz force law to spin it inside the windings of the induction motor stator. It's speed is governed by the frequency of the AC current which is why AC induction motors are usually constant speed motors. Here's a good link to find out some good backround information. (the video refers to 3 phase motors, but single phase induction motors work on the same principle... invented by Nicola Tesla... yeah, that guy. https://www.youtube.com/watch?v=AQqyGNOP_3o One of the problems is that this rotor can not tolerate grounding out against the stator because it's not a rotating magnet with a fixed magnetic field, it's a wire cage with an induced directional current. If the rotor grounds to the stator then the induced directional force is no longer in syncronization with the electrical field generated by the AC windings of the stator. SO,... what's the problem with this... I took my induction motor apart. I tested the windings for continuity and also for shorts to the stator plates and there was no problems with the stator, yet the rotor wouldn't turn and the motor would hum loudly. I inspected the rotor and it had "witness marks" at the top of the cage , and also corresponding marks on the stator plates, so the rotor was rubbing the stator. The problem with this motor is the bushing design on the top of the motor is a piece of crap. It's a steel ball that's fixed in place with a piece of spring steel. Over the years it's gotten sloppy, probably from me pushing on the sanding drum too strongly. The play worn into the upper bushing allows the rotor cage to ground out against the stator, causing friction but also shorting some of the induced Lorentz effect forces driving the rotor. The answer for me was to buy and install an oillite sleeve bushing from mcmaster-carr as a replacement for the manufacturer's upper steel knuckle bushing. This replacement eliminated the rotor contacting the stator, so now the motor starts instantly, and spins with less vibration than when it was brand new... Here's the bushing I bought listed below. https://www.mcmaster.com/6338K577 I had to ream the inner diameter of the bushing out a few thousandths to fit the shaft of the rotor. I wrapped sandpaper around a wrench socket until it was a tight fit inside the bushing, then I worked it inside the bushing until the enlarged inner bushing was a tight fit on the motor shaft. It took some time and patience. The bushing's outer diameter is also slightly larger than the case opening, so again I used sandpaper wrapped around a different diameter wrench socket to gently open the hole in the case to an interference size fit on the outside of the oillite bushing. I installed the flanged oillite bushing from the top side of the motor and used JB weld underneath the casting to fill in the tapered angle in the casting, so the bushing would be held solidly. Everything is working fine now. It starts instantly and doesn't vibrate or judder like it used to do with the original bushing. I don't think many other people will do this modification, but the fact that it repairs the issue with the humming motor that won't start tells me that I found the problem. The tell tale sign of this diagnosis is the witness marks on the rotor cage and the stator plates on the top edge of the motor near the bushing that I replaced. oillite bushing installed on remounted motor Edited February 13, 2020 by o0dude0o added a picture 1 Quote Link to comment Share on other sites More sharing options...
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