Originally Posted By: SHOZ
I would think the pot metal one would last years too. I don't see what happened as normal wear. Either a bearing is bad in the blower of someone in the past cracked that pulley trying to remove it improperly.
I inspected the furnace when I purchased the condo a year and 4 months ago and didn't notice anything. As brittle as this piece appears to be, I'd think that a crack due to improper belt changing would cause an immediate failure, as the crack quickly propagates. See below for additional discussion...
Thinking "out loud" here:
It was mentioned earlier that the sheave is designed to change the pulley ratio between the motor and blower, but it appears to me that it also serves to adjust belt tension.
The belt tension didn't seem excessive, but it was tighter than I'd expect for the duty (the blower assembly isn't very heavy and it spins with little resistance.) I don't know when this was last replaced, but whomever replaced it, they should have threaded the second half of the sheave to adjust tension.
The two halves of the broken sheave were as close together as possible, adding as much tension to the best as possible. It may be that this is what caused the failure.
I would think the pot metal one would last years too. I don't see what happened as normal wear. Either a bearing is bad in the blower of someone in the past cracked that pulley trying to remove it improperly.
I inspected the furnace when I purchased the condo a year and 4 months ago and didn't notice anything. As brittle as this piece appears to be, I'd think that a crack due to improper belt changing would cause an immediate failure, as the crack quickly propagates. See below for additional discussion...
Thinking "out loud" here:
It was mentioned earlier that the sheave is designed to change the pulley ratio between the motor and blower, but it appears to me that it also serves to adjust belt tension.
The belt tension didn't seem excessive, but it was tighter than I'd expect for the duty (the blower assembly isn't very heavy and it spins with little resistance.) I don't know when this was last replaced, but whomever replaced it, they should have threaded the second half of the sheave to adjust tension.
The two halves of the broken sheave were as close together as possible, adding as much tension to the best as possible. It may be that this is what caused the failure.