Mowing mower keeps throwing the belt

[Little Red Tractor]

I recently got a Cub Cadet 6824, and before mowing I replaced the spindle belt as the one on it was a bit chewed up. About 1000 feet into my first mowing of the year, it threw the belt. I reset it, and it did it again, again and again...and once more for good measure. All that in about an acre and a quarter.
The only thing that seemed to keep it on, finally, was running the engine just under the "green" range--about 2800 rpms or so.

The spindles appear tight and have been freshly serviced, The gearbox is tight to the mounting. I noticed that the pivot point point of the idler arm seems to be a bit wobbly, but that's about all I can find.

Any thoughts?

 

[Bird]

It's been a long time ago that I had a Cub Cadet doing that (late '90s). And it was simply pulley alignment. Once I figured out which pulley and got them all aligned properly, no more problem. I'm guessing you found your problem with that idler arm.

 

[TRR]

I'm not familiar with your setup, but I'm guessing that your drive pulley is on a horizontal shaft and your mower pulleys are on a vertical spindle. Thus the belt needs to make a 90 deg turn. Check the type of belt you are using. The automotive belts I believe are an "A" type belt and do not make that 90 deg turn without rolling over. You will probably need something like a "B" belt or wider. (If the other suggestions don't fix it.)

Conventional V-Belts - Belts Sizes A - B - C - D - E Section Belts

 

[Little Red Tractor]

I'm not familiar with your setup, but I'm guessing that your drive pulley is on a horizontal shaft and your mower pulleys are on a vertical spindle. Thus the belt needs to make a 90 deg turn. Check the type of belt you are using. The automotive belts I believe are an "A" type belt and do not make that 90 deg turn without rolling over. You will probably need something like a "B" belt or wider. (If the other suggestions don't fix it.)

Conventional V-Belts - Belts Sizes A - B - C - D - E Section Belts

Thanks TRR, but it's not the setup you're thinking of. It's a PTO driven deck, and I'm using the OEM part, so it's not an improper belt issue in any way.

 

[MarkV]

Had a similar experience with a Cub Zero Turn mower and it was a bad bearing in the idler pulley. Not sure of your set up but might check there.

MarkV

 

[yelbike]

Check for horizontal pulley alignment as well. Meaning the pulleys should be all be at the same elevation from the deck. Also check that they are all plumb, so each spindle is "square" to the deck plane. Thirdly, check each pulley running surface for wear, pulleys do wear out. How many hours??

Did you run it with the old belt? Although you stated its an OEM belt, counter parts people do make mistakes sometimes.

 

[scoops]

This was a known issue with the belts coming off, the fix was to add a pulley
I will take a picture of mine tomorrow to show you where the extra was placed.

My belt never comes off anymore.

 

[Little Red Tractor]

Check for horizontal pulley alignment as well. Meaning the pulleys should be all be at the same elevation from the deck. Also check that they are all plumb, so each spindle is "square" to the deck plane. Thirdly, check each pulley running surface for wear, pulleys do wear out. How many hours??

Did you run it with the old belt? Although you stated its an OEM belt, counter parts people do make mistakes sometimes.

I never ran with the old belt. It had a couple cuts, so I replaced it when I had the deck off the tractor to sharpen the blades.

 

[Little Red Tractor]

This was a known issue with the belts coming off, the fix was to add a pulley
I will take a picture of mine tomorrow to show you where the extra was placed.

My belt never comes off anymore.

Looking forward to the picture!

 

[ultrarunner]

Only a suggestion.

I had trouble with a mower that was throwing the belt... that is why I got it for next to nothing.

Putting a Gator Back Premium belt solved the problem...

Guess not all belts are created equal... the notched design allows for greater variance.

May or may not be applicable.