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Chemistry Electronics Services
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455A746 Gearmotor on "Maxi Rotator" Shaker Table, Thermo-Scientific Model 4631

I found an Allied Electronics replacement for the failed 455A746 motor in Thermo-Fischer 4631 shaker table (called 3D rotator.) These motors are no longer available from Thermo or from Globe Motor. Globe Motor catalog no longer lists 48V spur-gear motors. Neither does Pittman. However, a quick measurement showed that this 48V motor is only being driven at 16VDC at maximum, and has 64:1 stepdown ratio on the motor gearbox. If instead we use a 24VDC gearmotor, it will run at twice the speed ...so just use a 128:1 gearbox. If internal friction is small compared to the motor work done in lifting off-balance sample tubes ...then a 48V 64:1 motor draws the same current as a 24V 128:1 motor (if both are being run at 16VDC.) Externally the motors are the same, same flatted shaft, just screw it in.


NEW INFO! I replaced one of these motors in 4/2012. Five years later it has failed because of worn-out carbon brushes. We do run these tilt/shakers 24hrs per day. So, take note that a $200 motor will only get you five more years of use. I did manage to replace the carbon brushes in one of these. Requires disassembly of the motor. It's a mess: buildup of clots of fine carbon powder, like copier-toner. I managed to open the motor and replace them with brushes from a different motor, removing the spring and soldering to the copper braid. Also, cleaned out the carbon buildup from between commutator sectors, and smoothed the copper sectors with fine sandpaper on the lathe. We'll see if it lasts another five years.


on eBay: SKV71 carbon brushes .25" x .25"


Globe Motor 455A105-3, avaliable Allied Electronics: 70217722 $135





















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