Wednesday, August 5, 2015

Repairing the Tumbler Gear Motor

Thursday, July 16, 2015
I turned on the tumbler as I left at 1600.  About a minute later a heard a thump and the tumbler stopped turning.  I went back in and found the exhaust fan and the tumbler motor were still running.  I turned off the fan and the timer switch.  A quick inspection revealed a small ring of steel had fallen onto the chain and the shaft of the gear box broke off.  Big trouble.  I pulled the service cord to the motor and left for the night.

A neighbor friend, Tom, is an engineer retired from the army reserve.  He seems to know about everything there is to know about engineering and some other things too so I consulted him.  He agreed to help me take apart the gear motor and see what would be required to get the tumbler running again.

The next morning, Saturday, we took the gear-motor off the tumbler and disassembled the gearbox.  It is a right angle worm gear design. The damage was clearly visible.  The 1” shaft to the roller chain sprocket was broken and the brass gear had a number of sheared off teeth.  We did a lot of degreasing and put all the relevant parts in the vehicle but had to wait until Monday to consult with an industrial bearing company.

On Monday we learned that they don’t rebuild anything but would try to find parts for us but ultimately weren’t successful.  Tom did some further checking and gave me a number to call.  I called and found that a brand new synchrogear motor would cost $960 + freight.  The E435 gearbox alone would cost $480 + freight and that is what I ordered.

2 HP E435 Synchrogear motor.
Tom came over at about 1000 and we started working on the rebuild.  With one trip to a farm and ranch store we found all the additional parts we needed.  Finished at 1630.  A hard day with Tom doing most of the work. We added an idler sprocket to take up chain slack.  And we also made some changes in the guards so at the end I’m in better mechanical shape than before the break-down.
A painful experience like this should provoke some thinking about ways it might have been prevented or mitigated.  Considering that it took the two of us over six hours to complete the job I may well have been better off just buying a new motor.

It occurred to me that If I had built the tumbler in a manner similar to my hydraulic press and the reversing bar twister I may have been better off.  In those cases the motor connects to the driven component through a Lovejoy coupler.  That makes them modular so either component can be dealt with independently.

Motor-Coupler-Pump linkage.

Motor-Coupler-Reduction Gearbox linkage.

One last point.  Tom suggested a better way to control the alignment of the 2” shafts turning the cylinder - mount them with paired pillow block bearings on both ends.

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