Re: (ET) Pulsing

[Rob Brockway <getractor yahoo com>]

 Ok,
I had time to work on the tractor over the long weekend.  I found I had 
voltage at the motor terminals but the E20 motor was not spinning 
consistently.  This made me think the motor was the problem.  I 
temporarily set up an E-12 motor on the floor and swapped over the wiring. 
 The E12 ran fine with no load.
I pulled the motor out and did some testing tonight.  I did a 4 point 
resistance test.  Years ago I got approx. .07 ohms.  Tonight I got .08 
ohms in most shaft positions but as high as .58 in one position.  I think 
that is where the pulsing came from and the failure to start sometimes.  
The commutator is grooved.  One brush feels good.  The other does not feel 
like it slides in and out smoothly.  I believe I have a new set of brushes 
on the shelf.
Any tips for what to look for in the brush holder and how it should feel?  
Is it possible to find a replacement brush holder?  I can turn the 
commutator on my lathe but how critical is it to undercut the commutator?
If I have problems repairing, any recommendations for a replacement motor 
such as a Motenergy ME0909/1906?
 Thanks,
Rob Brockway

    On Wednesday, August 14, 2024 at 04:04:58 PM EDT, Rob Brockway via 
Elec-trak <elec-trak cosmos phy tufts edu> wrote:  
 
  I have a Curtis 1204 set up with traditional contactors feeding an E20 
motor.  Under high load conditions climbing a hill or when the battery is 
50%-70% drained I am getting a pulsation perhaps 2-5 hz.  You can feel it 
and see it on the load meter.  I have not had time to make diagnostic 
measurements yet.  Has anyone run into this before?  The consistent pulse 
makes me think it is the controller.  The controller is 16-20 years old 
and I am wondering if it may be failing.  Any input is appreciated.
Rob Brockway
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