“There was a strange noise in the gearbox and the hoist stopped.” Our longtime customer called with a number of symptoms affecting their Coffing EC Electric Chain Hoist, but the gearbox noise was an unusual complaint. While the hoist operated properly to go up, it would not go down.
A mechanical investigation yielded surprising results: A thrust bearing from the geared limit switch shaft dropped into the gear train and clogged the gears. Since this should never happen, it’s clear that someone removed the end cover and the geared limit switch. They likely pulled on the shaft (see #37 in the diagram below) causing the thrust washer (#23) and thrust bearing (#24) to drop into the gear train and create a jam.
We inspected the mechanical load brake, the remainder of the gear train and the geared limit switch. Except for the thrust bearing, everything else appeared to be in good condition. The hoist’s gear train was saved by the slip clutch, which allowed the hoist motor to turn while the downward motion gears were locked. This standard feature of the American-made Coffing hoist prevented what would have been destruction on more cheaply made brands. To return the unit to working order, we reassembled it with new thrust bearings and washers, set the upper and lower limit switch, and ran a load test.
It’s key to note that this problem was caused by someone who opened the unit, likely to repair it, but was unfamiliar with Coffing brand hoisting equipment. It’s our experience that anyone not factory-trained in the mechanical workings of a hoist can do more harm than good, often leading to more costly repairs or replacement. Hoist Manufacturers, such as Columbus McKinnon, the maker of Coffing Hoists, offer technician training and certifications to ensure that end-users can find quality repair services.
Shupper-Brickle Equipment offers repairs by certified hoist technicians. Contact us for more information on our services or OEM parts.