Finally got that weird hum out of the gearless unit at the old library building

Spent three days last week on a 1980s Otis, and the sound was driving everyone nuts. Turns out it was a slightly worn motor coupling that only vibrated at a specific speed. Anyone else run into a noise that was super specific like that?

3 comments

3 Comments

wesley_grant331mo ago

Ever check if the motor mounts were still solid? On an old Schindler I worked on, a cracked mount let the whole assembly shift just enough to cause a gear whine only when the car passed the counterweight. That one was a real head scratcher.

richard_wells594h ago

But wouldn't a bad mount cause noise all the time, not just at one spot? That shift would be constant. Sounds more like something in the rail or guide system that only gets loaded a certain way. Those old units can develop a harmonic vibration at a specific speed and position.

karent751mo ago

We had a 90s Dover at a medical center that only made a high pitched whine on the down run between the 4th and 5th floors. It was a bent guide shoe that just kissed the rail at a certain angle under load. Took forever to find because it was silent on the way up.