At 6:40 a.m. I chased a “bearing failure” squeal on a 5HP cyclone, only to find the drive belt harmonizing with the motor pulley because I’d left the tension about 3 mm shy after a cleaning. On the bright side, the whole shop now knows what 60 Hz plus a glazing belt sounds like — anyone else diagnose by pitch before grabbing the straightedge and a dab of Loctite?
@OP If it’s singing at “60 Hz”, dust the belt with talc — if the note dies instantly, it’s slip, not a bearing; then let it warm 2–3 minutes, re-tension, and run a straightedge across the sheaves. Caveat: belt dressing just hides the problem; a cogged AX belt resists glazing better — are you running one?
On my 5HP cyclone, if it starts that “60 Hz” croon, I crack the motor bolts, kill power after a 30‑second warmup, then bump the motor forward and tighten while the belt’s still warm; a quick Sharpie witness line across the motor foot and base tells me if it creeps back that “3 mm shy.” Small caveat: easy on tension or you’ll cook bearings — curious if yours has a slotted base that likes to slip, @OP.
That 6:40 a.m. 60 Hz whine is brutal, . Before I touch tension, I deglaze the sheave grooves and belt — quick scrub with a green pad and alcohol — then re-seat; half the time the “glazing belt” song stops cold. If you like pitch-diagnosing, @OP, try the sonic method with a phone app and Gates’ chart: https://www.gates.com/us/en/resource/belt-tensioning.html — ever tuned by span frequency?
Tried a raw‑edge cogged BX belt yet, @OP? I killed that “60 Hz choir” on my cyclone by swapping to one — grips better, runs cooler, and the note disappears even a hair under‑tensioned. Only caveat: they can hiss faintly at idle but won’t glaze like smooth belts.