314-H snapping drive belts

[Handy Don 12,445]

Nothing wrong with reviving a relevant thread that's gone quiet.

 

Belts come off because the belt is damaged or else the alignment is off, i.e. something is worn, broken, or bent.

 

That the direction of rotation made a difference, signals belt damage as the place to start. Look closely for a "wiggle" in belt that would indicate broken cords internally. This can be a manufacturing defect but is more common from someone exerting too much force at one point trying to mount it. Sometimes a shady person will return a belt they've broken like this and it'll get restocked.

 

That said, a dented pulley or a bent idler support (caused by the failure of the old belt?) cannot be counted out. Also look for play in the thru-tractor arm that supports the idler--it can be tricky to detect with the tensioner spring attached so remove that first. I've replaced one of these and added bushings at the frame due to wallowing out.

 

Good luck!

 

[HankB 16]

Hi Don,

I agree with all of your suggestions. I've inspected everything you listed and was unable to identify any problems. When it's running, the belt runs over the idler with no side to side movement. Nor was it necessary to apply much force at any time during installation. I did loosen/remove the guards by the engine pulley so I didn't need to force the belt at that end. The belt didn't need to travel to a weak or damaged spot to walk off the idler so any condition with the belt that causes this is distributed along the entire length. All I can think is that the cords or some portion of the composition is off center causing it to move to one side.

 

Thanks!

 

 

 

[Handy Don 12,445]

5 hours ago, HankB said:

All I can think is that the cords or some portion of the composition is off center causing it to move to one side.

 

If this is the case, I'd expect to be able to observe it as the belt moves onto and off of the pulleys. It would seem to be tilted as it enters or leaves the groove, sit slightly crooked in the groove, and/or show signs of trying to climb out of the groove--and it would be under load that it'd be easiest to see.

 

Not being something that happens at a particular spot on the belt, though, makes me question the pulleys' alignment. With the guard off, can you put a straightedge against the faces of the drive and driven pulleys to see that they are in the same plane? Then also check the idler/tensioner?

 

Any dents or wobbles or rough sidewalls on the pulleys -- observe them when rotating slowly. To "feel" the engine pulley, I've used a piece of wooden dowel riding gently on it while it's turning.

 

Recognize that even a relatively short time of use under bad alignment or with a damaged pulley can affect a belt, especially if it was under load.