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Spindle pullies hot... normal?

9411 Views 14 Replies 7 Participants Last post by  jgayman
Since I've been mulching leaves with my X500 & 48-inch deck, I removed the plastic covers over the two outer spindles. This allows easier removal of the leaf debris.

I noticed that even on a cool day the outer spindle pulleys are very warm to the touch after running for only around 5-mins. After a mulch session they are too hot to touch.

Is this normal?

Obviously I was never able to touch them prior to removing the plastic covers.

I could see them getting hot after 1-2 hours mowing but the fact that they were warm after only 5-mins has me puzzled.
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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.
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?
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.
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