Re: (ET) Mower motor mayhem (maybe)

["Christopher Meier" <mr23 mn rr com>]

Wild guess: brushes stuck?

----- Original Message ----- 
From: "Chris Zach" <czach computer org>
To: "Elec-trak list" <elec-trak cosmos phy tufts edu>
Sent: Wednesday, April 07, 2004 6:59 PM
Subject: (ET) Mower motor mayhem (maybe)


> Well, I drove the tractor down to the shed, dropped off the blower and 
> mounted the deck. The deck has spent the winter on it's side in a nice 
> dry shed.
> 
> Hooked it up and powered it up. Sounded wrong. It would pull mower deck 
> current, but the needle was "spiking" every 20 seconds or so.
> 
> Checked the deck. The center motor was spinning normally while the outer 
> two were not. They would start to spin for a few seconds, then shut down 
> as their thermo-breakers tripped.
> 
> Tried the deck at 12 volts. All blades spun fine. Interesting. With the 
> mower unplugged, turning one blade would cause the other two to turn. So 
> bearings were ok.
> 
> Then I tried bypassing one of the thermo sensors, thinking they were 
> bad. Plugged into 36 volts and fired it up.
> 
> Blades spun up fine but motor started to smoke in seconds. Shut down, 
> wires to it were hot.
> 
> Whoah. Reconnected the breaker and tried again. Once again motor would 
> spin for a few seconds then trip. Looking in the little inspection port 
> I could see sparks on the commutator.
> 
> What happened over the winter? And why to two motors?
> 
> Chris
> 
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