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Re: (ET) one blade not cutting well
On Wed, 26 Jul 2006, Konstanty, Walter (GE Indust, ConsInd) wrote:
This thread is getting so long I can't remember the key points anymore...
Sorry :)
- Blades are turning all same way?
Yup.
- Switch motors around may isolate the motor
Yeah, I've been thinking about doing that - will leave it as the last
thing to try, since it's a bit of a pain removing the motors out of there
(well, mostly putting them back in).
- Switch blades around may isolate a heavy/bad blade
I'll try that, but since the right motor had the problem both with the new
Gator Blades, and also with the old Elec-Trak blades, I assume it's not an
issue with just the blades - otherwise I would have coincidentally had
both a bad Gator Blade and a bad original Elec-Trak blade, and
coincidentally put both of them on the same motor.
- Armatures really don't "get tired"....current flows to maintain
terminal volts/speed
and if shorted, they blow up (go to ground, melt, etc)...if the
That's what I figured - that either the Armature is fine, or it's
completely toast (ie. short across the coil somewhere, bad bad bad). Since
the motor is at least spinning decently, I assume the armature is fine.
Magnets could be weak though.
permanent magnets get weakened, speed increases but torque decreases.
That seems like a fairly likely option. Hmmmm.... do both sizes of deck
motors use the same magnets? I have a spare small mower deck motor sitting
around, could pull the magnets from that one if they're the same as the
magnets in the big ones (which is what I have in the deck now).
Magnets get weak from removing the rotor too many times or external
demagnetization.
They should also get weak over time just from use - the act of using the
magnet to exert a torque on the armature will gradually demagnetize the
permanent magnets, just as if you put some bar magnets in storage lined up
with the north poles laying on top of each other, and south on top of each
other, such that they're constantly pushing on each other, they'll
gradually demagnetize.
- Measuring motor currents lets you know load between
motors...
I'll give that a try tomorrow or Friday - I'll try just using a multimeter
in series with a motor as an ammeter, to avoid buying a shunt or one of
those pricey clamp on DC ammeters (that presumably is a Hall Effect probe
- heh heh, in one of the physics courses I'm teaching right now, we'll be
going over the Hall Effect tomorrow. We've been going over circuits, and I
gave them a problem this week to help understand power usage in circuits
based on how the Elec-Trak controls the speed of the drive motor (well, in
the first three speeds, by bypassing resistors to increase the current
through the motor)).
measuring speed also would be "neat". - Rear or side discharge
may affect the right-most motor more if all grass thrown that way. -
Friction or bad bearings show up quickly.
It has a side discharge slot, but I have it plugged up with the plate that
you can cover it with - which presumably makes it a rear discharge one
(that's where all the grass is coming out). I didn't put the grass guides
back in after the restoration, which I'm thinking could be part of the
problem - the grass isn't being guided out towards the rear of the deck,
so it's all getting chucked at the right blade (the one having the
problem). I'm thinking I should just try putting the guide back on and see
if that resolves it. If it does, I'll paint it with POR-15 and leave it
on. The main reason I didn't put it back on was thinking the Gator Blades
are a bit longer, so might smack into the guides (I think they would - but
I can always use the original blades if that resolves this issue).
Has anyone else who has removed the grass guide had this issue?
(the rightmost blade not cutting well, and if using Gator Blades, the
grass clogs in the teeth on the back of the blade, presumably due to it
turning slow and having all the cut grass chucked at it).
Maybe we all need PLC upgrades to monitor motor temperatures, load,
speed, amount of grass cut/snow plowed...that would be real neat.
:-D
Anyone want to develop a nice PLC module for monitoring those
things?
Thanks,
Mike