Friday, September 16, 2005

OK, So I’m Not An Electrical Engineer

I don’t read schematics and I’m not an electrical engineer. I didn’t order the wrong part. I just didn’t order all the parts I needed. On the schematic it shows “Bushing/Bearing”. I thought this was both the bushing and the bearing. The bushing is the plastic part that melted and the bearing is the damaged part that seats inside the bushing. I thought I was ordering both. $2.60 did seem cheap, but I had to replace a broken sprocket on the planer a few months ago and that part was less than $5.00 so I didn’t really question it.

Part 1 of this story.
Part 2 of this story.

Well, the “Bushing/Bearing” arrived today and it was just the plastic bushing and there was no bearing. On the invoice it was listed as a “bearing bushing”. So I went back to the schematic and noticed that the bearing is actually part of the “Armature Assembly”. The Armature Assembly is almost the whole freakin’ motor inside the housing. The Armature Assembly and the Field Assembly make up about 95% of the motor inside the motor housing. The bearing is at the end of the Armature Assembly and can’t be ordered as a separate part. This means I need to order the Armature Assembly. That is $68.91.

After getting the price on-line I started to think that maybe I’m in over my head here. I’ve never worked on an electric motor before. The $2.60 (about $8.00 w/ shipping) was chump change. I figured, if it doesn’t work I’m only out the $8.00 and the motor is in no worse shape, so what the hell. Nothing ventured. Nothing gained. Right?

With the Armature Assembly it’s a whole new ball game. I’m approaching half the cost of what I paid for the table saw in the first place. If I order this part and it doesn’t work it’s like throwing money down a hole. Not only am I out the $80 but that is $80 I could have spent towards the cost of a new table saw, or the cost of a whole new motor. What to do. What to do.

I decided I would first make sure I could get the old bushing out and the new bushing in. To do this I needed to get the Field Assembly out of the housing. To date I had only removed the Armature Assembly. It actually took me several minutes to get the Field Assembly out. I’m always nervous that there is going to be something spring loaded in there and several parts will shoot out in several directions all over the shop. There were no springs but there were a few electrical connections that would have been easy to disconnect if I had fingers that where 8-inchs long and as thin as a pencil.

With the Field Assembly out I was able to get the old bushing out and glue in the new one. I then quickly put everything back together before I forgot how it all went together or before I lost any parts. After it was all back together I’m actually feeling pretty confident about this. I have completely disassembled the motor, replaced 1 of 2 damaged parts, and put the whole thing back together. In theory, it should run if I plugged it in. However, I would ruin the new bushing I just installed so I decided not to. Even without electricity applied to it everything spins just about the way it did last week when I first removed the motor from the saw. So I ordered a new Armature Assembly. It should be here early next week. With any luck I will be back risking my fingers on the table saw in no time.


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Gary said...

Damn! You got blogspammed and that is after having word verification.
You know, if the saw doesn't work you can always go back to training hamsters to drive the belt wheel.

ben said...

When I was a kid, I took apart one of my favorite wind up toys. When the spring shot out, followed by a kazillion gears my heart just sank. I never did get it back together. But then in machine shop class we rebuilt a 2-cycle lawnmower engine. Since I provided the rusty engine, I was chosen to pull the start cord. I thought for sure the piston was going to fly out and kill me - obviously it didn't and the mower worked great.

So good job! Glad you tried the tear down and rebuild before spending good money. Who knows what else you might be able to fix now: washer, dryer, fridge, DVD player...

Anonymous said...

The word verification is too easy to decipher. :-P I could train software to do it. It's not going to help any against blogspam until it gets harder to read.

Greg said...

I had turned off Word Verification for a day or so. The "Word Image" was not being displayed and I could not post a comment to my own blog. I guess I forgot to turn it back on and I got spammed.

Blog spammers seem like lonely, desperate people.