Mk5 motor is dead

[trainguytom]

Pulled stuff apart, used a multi-meter and have power to the leads going into the motor. Blew out the dust/crud, tried one more time. Nothing.
as long as it's all apart, I'm going to simply switch in my spare motor. After all, that's what Ive been keeping it for.
Thanks for the ideas.

[JPG]

What is the resistance across the motor power input wires?

[trainguytom]

Well, I took the motor out of the metal shroud so I could switch to my backup, and that gave me better access to the vent slots in the motor case, so I figured I've got nothing to lose by giving the motor one more really thorough blow out....and BINGO! Off it went. Running perfectly.

A little surprising in that I keep the headstock insides pretty clean and when I first opened it up, there really wasn't much sawdust accumulated around the motor. Even when I first blew it out, there wasn't much and the final time there wasn't much either. I guess it doesn't take much if it's in the right(wrong) place.
Oh well, lesson learned. Back to building stuff.

[everettdavis]

The centrifugal motor start switch has a set of normally closed contacts that open as the motor starts spinning up due to mechanical fly weights physically acting on the rotating assembly, which disconnects the start circuit as it comes up to a threshold speed.

Normally, the contacts come back together due to the spring action of the assembly restoring the start circuit when the motor powers off.

I said normally.... If there is an accumulation of debris of some nature in the area of the switch, something can come between the contacts preventing them from closing back, or grime can bind up the mechanical movement and cause it not to move the full range, again holding them open.

Without that start circuit restored, your motor will not run. I suspect that you had something affecting that mechanism that you cleared out with compressed air.

Take a peek at http://www.shopsmith.com/ss_forum/viewt ... 95#p240895 and look at the SHOPSMITH MOTOR GUIDE work in process.pdf which is a work in process document that I have deferred to finishing at a later date, but it will give you some insight into the direction I am taking the project in the future. I have come to the conclusion that I need to procure more of the motor models and do a lot of the documentation on them myself.

That said, there is a ton of educational front end motor discussion relative to understanding motors in general and an electrical discussion in it already that can clear up some questions for many.

Glad you got yours working!

Everett

[dusty]

Well done, Tom. Now you can make more of that "Sawdust".

[JPG]

. . . I turned on the switch, and nothing. No spin, no hum, no apparent power.
My first thought was look for the obvious. That the switch went bad, or the cord, or the outlet.
I got out a spare plug/cord & bypassed the switch right the motor leads and still nothing. No hum, just dead.
. . .

Since I believe the initial post, I fear the problem will return.

[trainguytom]

. . . I turned on the switch, and nothing. No spin, no hum, no apparent power.
My first thought was look for the obvious. That the switch went bad, or the cord, or the outlet.
I got out a spare plug/cord & bypassed the switch right the motor leads and still nothing. No hum, just dead.
. . .

Since I believe the initial post, I fear the problem will return.

I'm not sure what you mean. If, as it appears, that the issue was dust/crud related and I was able to blow that out & it now starts & runs fine, why would the issue return?

[JPG]

. . . I turned on the switch, and nothing. No spin, no hum, no apparent power.
My first thought was look for the obvious. That the switch went bad, or the cord, or the outlet.
I got out a spare plug/cord & bypassed the switch right the motor leads and still nothing. No hum, just dead.
. . .

Since I believe the initial post, I fear the problem will return.

I'm not sure what you mean. If, as it appears, that the issue was dust/crud related and I was able to blow that out & it now starts & runs fine, why would the issue return?

Note the bold text in the quote of your initial post. Key point is 'no hum'.

IF the cause of 'no run' was crud in the start switch contacts, it would have 'hummed'. Since you stated it did not hum, then blowing out the dust etc. reconnected whatever was disconnected.

Now IF it did hum earlier then it might not come back. Only thee knows which is the case.

[dusty]

crud in the contacts = no current through the contacts = no current in the "start" winding = no start.

I don't expect the problem to return. No hum + no motion was the first clue for me.

[JPG]

crud in the contacts = no current through the contacts = no current in the "start" winding = no start.

I don't expect the problem to return. No hum + no motion was the first clue for me.

The RUN windings are directly connected across the power input wires. When those wires are energized, the motor hums quite loudly.

Only the start circuit is affected by the start switch.

Do recall the admonition to NOT leave the motor energized when the start switch is open since the run windings will 'fry'.

No hum means the run windings are NOT being energized. Only the power cord, plug, power switch and splices will cause that(as well as a dead outlet).

It may not return, but we know not why 'no hum'.