Re: (ET) Mower motor problems

[David Brandt <ev_dave13 yahoo com>]

Mine resonates as well.  The motors turn at slightly different RPM's due 
to the slight manufacturing differences between them.  the resonance you 
hear is called beating, where the frequencies drift slowly in and out of 
phase, and on mine, it actually shook one of the bolts almost all the way 
out of a support arm!

There isn't much you can do about it, it is due to the very slight RPM 
difference.  A stiffer deck would help, as would using lock nuts.  An 
anti-vibration gasket (say 1/8" thick rubber) between the motor and deck 
might also help, but adjusting the motor height would be difficult 
afterwards.  Me, I'd use locknuts and live with the vibration.  It isn't 
near as loud as an ICE mower.

David Brandt


--- On Mon, 11/2/09, Stan Witherspoon <stwspoon speakeasy net> wrote:

> From: Stan Witherspoon <stwspoon speakeasy net>
> Subject: (ET) Mower motor problems
> To: Elec-trak cosmos phy tufts edu
> Date: Monday, November 2, 2009, 12:21 AM
> I have been having mower motor
> problems. I have replaced the bearings, replaced one brush
> housing, had the same magnet in two different motors come
> loose, and now the magnet in one of my my replacement motor
> housing has come loose as well.  This is in less than
> 12 months and less than 10 mowings. I can't seem to get
> through a single mowing without having to fix something.
> 
> I realize these tractors are pretty old, but I would expect
> that stuff that gets fixed would stay fixed.  Is there
> anything I need to watch out for on the mower motors? I have
> been through the HSM and all of the on line archives. 
> My mower deck has a loud rhythmic vibration that resonates
> every second or so that goes away when the motors are loaded
> down, like when mowing thick grass. I have balanced the
> blades, replaced the blades, balanced the replacements,
> disassembled, cleaned and reassembled the mower deck and
> replaced the wiring on the mower deck. I also have new fiber
> washers and I torqued the blades bolts according to the HSM
> specs.
> 
> Any Suggestions?
> 
> Frustrated,
> 
> Stan
> 
> 
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