Electric motor repair - Rigid table saw - Page 2 - PeachParts Mercedes-Benz Forum

spdrun · #16 03-10-2013, 04:34 PM

Quote:

Originally Posted by Rob Pruijt

You are really attached to your saw.

Or maybe just attached to the idea of not giving people in an enemy country another $500 for a tool that will fry just as quickly.

cmac2012 · #17 03-10-2013, 04:44 PM

Quote:

Originally Posted by Rob Pruijt

You are really attached to your saw.

I'm no expert and wasted lots of time tying to fix electectric motors until one of my very technical friends gave me a quick course.

He had some practical tips:
1
Never touch the cummulator, maybo with a copper brush, but not with sandpaper or a file.
The only way to get it smooth again is with a percision (expensive) lathe. The tolerances for roundness are measured in micrometers. If it off the brushes will start to float, produce sparks and wear out very quickly. Also most of the power will be lost.
2
The only thing that can be repaired on these (I think they are called Universal motors in enlgish) are the brushes and bearings.
3
Wear on the cummulator is ok, it doesn't have to be smooth, only round.
4
Smoke is bad, in 99.9% of the cases the motor is toast. Be carefull with the smoke, very unhealthy.

There are a lot of different types of electric motors, each with specific advantages and disadvantages.

If you have a brushless motor like used in a fan, never let it run without the fan attached. It will spin out of control and can even disinterate.

Rob

Unfortunately, you've been spot on in all of this. I like the saw, it's been good to me, and I'm not keen on pulling out a spare $500 right now. But you're right, time to let go (brushes away tear

). I put it all back together and it sparked large, making a hell of a racket. I tried a bit of cheap lathe action with my jig, using a file with some anchoring and slight pressure to round it up. Probably wouldn't have mattered, I suspect you're correct, that a short occurred somewhere in the coils.

I think I gave it a little too much use at once a few days previous. I dado-ed off about 1/4 inch thick of plywood off an area about 5" x 35". Didn't seem like it was straining that much but at some point in that I heard the motor falter a bit. I shut it off and continued without incident a few minutes later. I tend to get in too big of a hurry sometimes. Not wise.

I am a bit shocked that a new motor would cost almost as much as a new saw. I was thinking maybe $200 for a new motor might be what I was looking at but no . . .

Dang.

cmac2012 · #18 03-10-2013, 04:51 PM

Quote:

Originally Posted by spdrun

Or maybe just attached to the idea of not giving people in an enemy country another $500 for a tool that will fry just as quickly.

I found my receipt. Bought it 3/23/03. Real close to 10 year ago. I've used it quite a bit. If I'd been a little smarter, might still be going strong. I should have replaced the brushes a few years ago, not that it would have made a big difference with this incident but they were getting down there.

Rob Pruijt · #19 03-10-2013, 07:24 PM

If you only use it stationairy you may want to upgrade to a better saw, belt or chain driven. They are stronger, quiter and last much longer (and the motors can be easely replaced).

You may find a good used one for not that much money.

Rob

cmac2012 · #20 03-11-2013, 02:28 AM

There are a couple of stationary Ridgid saws on local Craigslist, both around $350. I just bought another portable model however - $499 before tax. My shop is not large and I often need to stash the saw in a corner. I would love to have a stationary model with a large outfeed table - someday. Also, with construction picking up I may be able to get on with a big company again and a portable saw is a plus there.

The new model is somewhat improved over the previous - one small but welcome change is the ability to lock the blade height. On my previous unit, vibration would tend to make the blade lower. On rabbiting cuts can be a pain.

Oh wow - just checked ereplacements.com and you can get a new armature for my new saw for $118. Not for my old one however - I'd already checked for that.

Rob Pruijt · #21 03-11-2013, 07:31 AM

Quote:

Originally Posted by cmac2012

I shut it off and continued without incident a few minutes later. I tend to get in too big of a hurry sometimes. Not wise.
Dang.

I'm afraid your right.

Letting it cool for a few minutes is not enough, it takes at least an hour to cool down when overheated.

With most universal motors the armature and cumulator are pressed on the shaft, when overheated they will get loose. Under heavy load they may rotate against each other putting a lot of strain on the wires. Especially when the insulation get a bit brittle this will kill the motor.

On expensive hand tools the armature and cummulator are spot welded on the shaft to prevent this.

Rob

kmaysob · #22 03-11-2013, 08:59 AM

throw the rigid junk in the the trash and look for a 20 year old craftsman, delta , rockwell ect.... i will never give rigid my money again. everything i have bought was either a pos or failed in short time.

cmac2012 · #23 03-11-2013, 12:46 PM

I dunno. My first one gave me some heavy service for 10 years.

If I had a bigger shop, I'd get a big older stationary saw.

barry12345 · #24 03-11-2013, 01:15 PM

Try some of their service outlets for a cheaper source motor. The prices you are being quoted are very high for a one horse motor.

cmac2012 · #25 03-11-2013, 01:23 PM

They are high but the hypoid gear and bearing input are needed for a trouble free installation. Any other motor would require some serious machining to install. The motor in my new Ridgid looks a lot like the one in my old one. One small difference, the brushes are removable from the outside of the case. Still, I may be a fool but I'm tempted to take the new one apart and compare the armatures. A replacement armature for the new model is available for about $120. That would be an acceptable price to pay to get my old one working for a jobsite beater.

My other fantasy is to cut the end of the shaft off the old armature - the gear and bearing - and have them welded onto a new motor. Don't think I have the equipment to align it myself and my welding is not top of the line. OTOH, getting this done for $200 or less might be tough. And then I'd have to make it work.