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  Electric Motor Repair & Refurbishment Ideas & Methods


Ever wonder what magic those motor shops perform on the electric motors in your Beechcraft? Well wonder no more, here is an array of equipment and methods used by Kevin O., a Beechcraft owner to keep electric motors operating at top form. Pireps of 7-8 seconds retract time have been reported on his rebuilds. Email him HERE for info on how he can help you with your electric motors.



Here is his narrative (and yes, of course he is A&P supervised) :


1st picture is of as removed armature. Remove Bearings


Clean it in a ultrasonic ammomia bath for 20 minutes



check segments of armature for shorts or breaks using a armature growler


                   As Removed Armature                                                           After Clean Up





Dry it in lab oven for 1 hour at 180 degrees






Check segments of armature for shorts or breaks using a armature growler





Then take the armature and true it in the armature lathe and also cut the mica to the correct depth--after that he checks it to make sure it is still within spec ( greater than 1.00" diameter)


Then it gets checked on the growler again



The armature then gets new bearings--the housing is cleaned and any worn wires are replaced the motor is then reassembled its run in one direction at 3 volts for 15 min--then the other direction for 15 minutes--it is then brought up to speed at 14 volts and run each way for 1 min. The dynamic brake is also checked both ways--if everything checks out--the motor is taken apart and cleaned again and reassembled--its run up again to check for vibration , etc



Some of his refurbished/repaired motors


Left one is a flap motor, center one a gear motor, right one is a flap motor from a 47 bonanza.




This was just a brief show of what he does--- He has a check list of over 20 items that are checked.




A landing gear motor is then taken to the blue fixture pictured below -- attached to a gear transmission--run up and down to make sure its producing the right torque and the dynamic brake is working under a load.


Note the weights on the fixture equal the weight of both gear and have the same arch as the gear does (swing).



Below is a video of Kevin testing dynamic braking of one of his refurbished 12V motors. Notice the torque his hand experiences when the motor is stopped. Don't even think about holding a 24V motor in your hand while testing dynamic braking!





Here is what one Beechcraft owner who has opened up a lot of these motors, thinks about Beech gear motor brands:


"had several to play with today--3/4 of them would run , but no dynamic brake----started switching parts around with the few good electomech motors I have---turns out that the armatures on the bad motors were the problem---they tested fine on the growler ( no shorts)--but had higher resistance than the good armatures----my thought--when the electromech have a problem (due to bad brushes or contamination of the armature) they would lose dynamic brake--this causes the gear to go too far and hitting the stops in the trans---it then takes a higher current to get it to move off the stops--this higher current causes the armature to heat up--screwing it up someway.


The lamb armatures are a more robust unit--even though some are 50 years old--you can tell someone took pride in what they were doing--I almost never find a bad Lamb armature--they just get worn down below service limits--this usually happens after 4 or 5 OHs."



This is a picture of a data plate from an early Bonanza (circa 1947) gear motor---its a lamb motor made by Black & Decker!


Who knew????



Happy Electric Motor Skies!




Why Continuing to Replace Gear Motor Brushes is not Such a Good Idea!


This is what the motor refurber with the above equipment found when he opened up a 12V landing gear motor and NO, that's not a fire ant dirt mound




This is a classic case of several motor brush replacements without a complete open up and cleaning and servicing of the motor.


The motor's owner reported that it would not work every once in a while, it was slow on RPM, had little to no dynamic braking, and was low on torque.


After cleaning the armature three times to get all the gunk out of it, installing new bearings, new brushes and running them in, this refurbisher returned the motor to smooth "sewing machine" operational status.


Below is the World Record Holder for gear motor brush debris. No folks, the brushes don't vaporize into a gas and escape out of the case!




Below is a classic case of running a gear motor to FAILURE , rendering the armature useless for further service via refurbishing/overhaul.

Gear motor cores are becoming scarce and running yours to

failure just makes it ever more difficult to provide economical

rebuilds to the Beech community.


If you or your mechanic insist on overfilling the transmission, you run the risk of trashing your gear motor by having the gear lube enter the motor and then BAM, your fresh overhaul landing gear motor is fouled and then fails because your motor mounting flange looks like the one below.






If your mechanic tells you he inspected the motor brushes and they looked good, ask if he looked at both of them because only one is easily accessed. Of course, if he completely removed the motor, both can easily be inspected.




Here is a parts diagram explosion of the gear motor:




Let's Run the Gear Motor Brushes to Failure!




Here is what Kevin O. reported in finding a Bonanza fuselage caused by a so-called "nose gear failure". Here is his narrative:


The nose was all screwed up from where the nose gear failed. I tested the trans with the manual handle---stuck solid--thought the wreck might have screwed the sector gear ???


Took off the gear motor--then the trans worked perfect and smooth ??? This above picture is what I found when I opened the motor up.


Brushes wore worn more than any motor I had ever inspected. One came out of the brush holder and shattered against the armature. Pieces of it had lodged and jamed up the motor so it could not turn--there was no way to do a manual extension with out removing the motor first ( good luck on doing this while in the air)


I'm sure the motor had been talking to the owner--His thoughts--if its not broke--don't fix it.


Listen to your motor--speeds--dynamic brake , etc. and if its got over 1500 hours on it--HAVE IT CHECKED!"


See the above pictures if you think just changing brushes is good motor maintenance



This is what a 50-year old 12V Bonanza flap motor looks like inside that has not been serviced in its 4000 some odd hours of airframe time.






This is what a severely abused flap motor looks like. Running components like this to failure is really doing a disservice to the Beechcraft community. It removes a serviceable core from the market which makes replacements scarcer and more expensive!




Click HERE for the 24V Baron Landing Gear Motor IPC and Maintenance Manual



Click HERE for the 12V Bonanza Landing Gear Motor IPC and Maintenance Manual



Folks, it doesn't have to be this way. Don't let your electric motors get this bad before giving them the service they deserve.



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