Spindle pullies hot... normal?

The friction from the drive belt entering and leaving the pulleys can warm them up pretty quick. More load on the mower blades means more horsepower handled by the belt and pulleys which adds to the heat load, as will the heat from the spindle bearings under load.

Add it all together and there is a lot of heat involved, and not a whole lot of airflow for cooling.

TUDOR said:

The friction from the drive belt entering and leaving the pulleys can warm them up pretty quick. More load on the mower blades means more horsepower handled by the belt and pulleys which adds to the heat load, as will the heat from the spindle bearings under load.

Add it all together and there is a lot of heat involved, and not a whole lot of airflow for cooling.

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Thanks! That was my initial theory as I figured there was no way the bearing itself could generate that much heat - and keep working.

I appreciate the confirmation.

Mrwiggles2 said:

Definitely use more grease than the manual indicates. My Wheel Horses get grease often and after use they get a blown off with my leaf blower. Helps keep debris off the deck. I'm always amazed to see tractor decks with three years of clippings on top.

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I can just imagine what the bottom of the deck looks like.

TJR345 said:

I can just imagine what the bottom of the deck looks like.

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Same here. I use the leaf blower to clean the deck and tractor after every use.

I had been keeping my plastic spindle covers on and while the leaf blower gets most of the crap out from under them, I finally wised up and removed the covers.

jgayman said:

Thanks! That was my initial theory as I figured there was no way the bearing itself could generate that much heat - and keep working.

I appreciate the confirmation.

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Umm. I suggest that you revisit your figuring. Those shafts turn at 3000+ rpm and the belt puts a substantial side load on the shaft when the blades are working hard. By contrast, the wheels on your truck turn at about 850 rpm at 70 mph with standard size tires. Ball bearings do not offer the same support, or heat distribution, that tapered roller bearings give, and the front wheel bearings on a pickup running down the highway in the summer are not subjected to as much horsepower load as the spindle bearings on a 3 blade mower deck

I've seen a pair of 3/4" air hoses blowing air at 90 psi at a new bearing on a 3" diameter shaft in an attempt to keep it under 250° while it was being run in. This was on a centrifugal (squirrel cage) fan supplying combustion air for a steel reheating furnace. A tradesman is assigned to monitor new bearings on these fans until such time as the temperature stabilizes, usually for 24 hours. That is his sole task for the shift. Can you spell b-o-r-i-n-g?

TUDOR said:

Umm. I suggest that you revisit your figuring. Those shafts turn at 3000+ rpm and the belt puts a substantial side load on the shaft when the blades are working hard.

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I agree. I know bearings can get hot.

I should have said "generate that much heat in that short of time". I understand how bearings get hot under heavy use. When I noticed the pulleys were warm I had only run the deck for about 3-mins.

I figured there was no way THAT much heat could be transferred from the bearing up through the shaft to the pulley in only 3-mins. If the bearing was generating THAT much heat it would be cherry red and smoking after mowing the yard.

Not necessarily. The rate of heat transfer is dependent on the temperature differential between the heat source and the cooling medium. At some point the temperature will stabilize. It may be high, but not necessarily so high as to cause damage.

Witness the temperature differential between a jet of cool air passing over a heating element. You can see the flow pattern of the air on the red hot element as heat is removed.

When I upgraded to a bigger engine. I used the same belt, which was in good shape. Mowed grass a few times with it and all was good. Then fall leaves came down pretty heavy, so I went out there to mulch it and the leaves actually pulled the engine down a bit. I was using the gator blades through those leaves and eventually the belt snapped. Do pulleys get hot?, you bet they do when you work them hard. Even the tips or cutting edge of the blades themselves were warm.

The one thing I like about mulching leaves. It shines the mower deck up underneath. I probably couldn't do much better with a sandblaster. I took a piece of 22 gauge sheet metal and formed it to fit over the chute opening. It helps keep the leaves inside longer to chop them up. Usually I see two little deposit trails under the mower deck.

Justy37 said:

The one thing I like about mulching leaves. It shines the mower deck up underneath. I probably couldn't do much better with a sandblaster. I took a piece of 22 gauge sheet metal and formed it to fit over the chute opening. It helps keep the leaves inside longer to chop them up. Usually I see two little deposit trails under the mower deck.

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X2 ! I was planning to take my deck off at the end of the season and clean it up but after mulching leaves it is clean as a whistle. There is not one spec of packed grass anywhere... even the nook and crannies are clean!