How would you solve this problem. Mower belts rubbing.

[4570Man]

I replaced the center pulley on my mower with a double pulley and got rid of the stacked center pulley which reduced the clearance. Now the belts rub against each other. Even before swapping the pulley the belts rubbed against each other evident by the abnormal wear on the belt. I’m thinking some rollers to hold up the brown belt would help but the roller of such small diameter would be spinning at a smoking fast rpm and probably wouldn’t last long. Any other ideas? ATTACH]594984[/ATTACH]

 

[4570Man]

If my math and assumptions are right the little roller would be going 11,650 rpm to match the FPM of the belt.

 

[CADplans]

Simply raise the double pulley until the brown belt clears,,
The belts can run out of alignment slightly,,, much better than having a bunch of rollers etc,,, pushing the belts around,,,:confused2:

 

[4570Man]

I already tried raising it about 1/4” to no avail. I may try raising it more. But my hopes aren’t good for that approach. But the more I think about the high rpm of the rollers I don’t think that’ll work either.

 

[rangerfredbob]

Add an idler pulley on the brown belt pushing it slightly up in the middle, V belts can take some misalignment without issue, something like THIS, just put a little off center pressure on the idler but space it up enough for the two belts to clear eachother. I just searched for V belt idler, here's another option. All it would take is one of those pulleys, a single hole in the deck a bolt and possibly some washers to get the right spacing...

 

[chim]

If the bottom sheave on that double is in alignment with the idler assembly to the right, how can the belts rub? It looks like you either have the double mounted too low or the shafts aren't all perfectly vertical.

I'm guessing that idler has a spring attached to the other end of that flat bar. Since the flat bar is on the top of the idler, the spring could want to lift the idler out of alignment if there's any play. Any chance the flat bar is bent or loose, making it higher on the end where the spring attaches? Any play in the bar / mounting? Bad bearings in the idler? It wouldn't take much. I just measured a double sheave from a deck I'm working on and the belts are only on 3/4" centers.

There may be something I'm not seeing - and that might be why the manufacturer used two sheaves.

 

[4570Man]

I had all the deck pulleys vertical until I raised it. The drive pulley doesn’t move when you raise and lower the deck so it doesn’t maintain the same height.

 

[chim]

OK, I was picturing the setups on my decks. They are PTO driven, so all the pulleys are in fixed positions.

From what you're saying, the drive pulley is on the tractor and is higher or lower (in relation to the other pulleys) as the deck is lowered or raised. Does the rubbing still happen when the deck is lowered? Could you raise the drive pulley on its shaft?

 

[Ford850]

Why not go back to the original design with a stacked center pully?

 

[chim]

Why not go back to the original design with a stacked center pully?

I wondered about that till I re-read the part where he said the belts rubbed before the swap. Right now I'm leaning towards believing the drive pulley is too low on its shaft. It's always a challenge to discuss a situation that's in a different ZIP code, even with pictures.