Author Topic: Gearbox cleaning  (Read 1856 times)

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Offline ericthetTopic starter

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Gearbox cleaning
« on: February 21, 2017, 03:41:53 PM »
I picked up a used liberty differential drive wheelchair and started stripping it down.  I added a Sabertooth 2x32 motor controller and noted that the current pulled on one of the motors was about twice the other one.  This wheel also ran about 10RPM slower and struggled more.  After taking it apart (I thought it might be the electronic brake) it appears it might be the gear box.  I only have the other motor to compare to but the gearbox takes about twice the power to turn and feels "sticky".  I don't hear a lot of grinding or mechanical noise it is just slower/gummier.

I did pull the gearbox apart real quick and noticed it full of gear oil or grease.  This is where I am kind of stuck.  I am not sure if the oil/grease is the problem (went bad?) or if maybe the bearings went bad.  My guess is the bearings as the oil/grease appears a healthy color.  However I don't know what kind of lube is in it or what to replace it with if I rebuild.

From what I can tell it is a 1:19.3 reduction (printed on a sticker) and the manufacture is MTM.  There is a serial code but searching doesn't pull anything up.  I am hoping to rebuild this gearbox as all the mechanics work nicely together.  I have a metal lathe (and know a bit how to use it) and have some basic mechanical knowledge. I am stronger in the electronics side which is why I am starting with this base to get going.

My big questions are:
1. What gear oil/grease should I rebuild this with and is there a way to tell what it is currently?
2. Is there an easy way to tell why the gearbox is struggling? 
3. Is there a way to test the bearings?

To rule out the motor I am thinking of putting the suspect gearbox on the good motor and vice versa and see if the problem persists with the gear box.  I am pretty confident it is, as the current was the same on both motors when the gear boxes were removed.  Also it is very noticeable that the suspect box has lag when hand turning.

For some reference the motors are 200W 24V.  With the gearboxes the good one only averages around 1-2 amps with no load.  The suspect unit was about 4-5amps no load and ran about 10RPM slower.  Without the gearboxes the motors were under 1amp no load. 

If I rebuild the one I might need to just rebuild the other if I need to ship bearings to get them to a known good state....

Any help would be.. helpful!


Offline rastas

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Re: Gearbox cleaning
« Reply #1 on: April 12, 2017, 05:19:38 AM »
ok clean out all of the old oil grease then clean with a solvent then see if there is any lumpiness growling stiffness etc look at the gears for any obvious damage same with the bearings
turn by hand
 also do the same with the other gearbox as if one is bad the other is not far behind
as for the type of grease go to a auto shop take a sample and ask for something similar 


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