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Malcolm Begg22/03/2020 21:47:14
15 forum posts
4 photos

I have a compressor which runs but the motor pulley gets extremely hot,the motor itself is quiet cool,I have replaced the bearings but the pulley still heats up?

Any help would be appreciated

Ian Parkin22/03/2020 21:55:44
974 forum posts
231 photos

Does the pulley on the pump get hot too?

john barnes 422/03/2020 22:03:01
32 forum posts
3 photos

Could the pulley be slipping on the shaft and causing friction. Check you have a woodruff key in.

Emgee22/03/2020 22:45:03
2148 forum posts
265 photos

Could be belt slip but normally you would hear it screaming so be aware.


Kiwi Bloke22/03/2020 22:49:05
602 forum posts
1 photos

...or the belt slipping. However, its more likely because V-belts heat up simply by deformed by their having to flex around the pulleys. Worse if the pulley is of small diameter and/or the belt speed is high, and, of course, the heat builds up as long as the belt runs, until heat loss mechanisms balance the heat input. For machines which run for a long time, hot belts aren't uncommon.

Nicholas Farr22/03/2020 23:51:06
2962 forum posts
1335 photos

Hi, Malcom, could be the pulley is worn? Does the bottom of the pulley V look shiny? If it does, then the belt may be rubbing on the bottom, which it should not do, there should always be a gap between the bottom of the belt and the bottom of the pulley V.

Regards Nick.

Kiwi Bloke23/03/2020 04:40:41
602 forum posts
1 photos

Forgot to say that internally-notched belts, being more flexible, run considerably cooler. Modern belts can take 60C running temp OK, but their life will be roughly halved.

Trevorh23/03/2020 08:46:54
303 forum posts
87 photos

Vee Belts if correctly aligned will last years

first option is belt dressing spray - prevents / reduces slippage and therefore running temp

second option check Tension - google for the correct deflection distance

if the above are good and good alignment then the only heat generated is as the belt is creating slight friction as it goes around the pulley's, they are designed for this

Easiest way to check for alignment is either a straight edge or piece of string

to use the string simply rotate by hand 1 pulley trapping the string under it, rotate to a mid point and now pull the string tight across the other pulley, look at the faces (edges of the pulleys and adjust until the string when pulled across both pulley's touches across both at the same time


not done it yet23/03/2020 08:57:44
6284 forum posts
20 photos

‘Extremely hot’ is clearly subjective. In my parlance, extremely hot would be damaging (or has damaged) the belt, for certain.

I carry dinner plates to the table with my bare hands, while my wife would be using insulated mits, for instance. Same temperature, different tolerance.

An actual temperature would be useful, as exaggeration often accompanies threads like this. Make and size of the compressor would help, too. Cheaper-end compressors run at high speed and/or use minimum-sized motor pulleys that are more susceptible to problems like this.

I would suspect that the belt has seen its day and needs replacing.

Howard Lewis23/03/2020 10:04:07
5238 forum posts
13 photos

As NDIY says, "HOT" is relative. If you can bear your hand on the pulley, it is probably below 80'C

The pulley will be warmer than its surroundings because of the friction between belt and pulley as it enters and leaves the groove..

My first suspect would be belt slip. This assumes that the problem has only just arisen, and that the belt is the correct section, so that it is not down in the bottom of the V groove. The back of the belt should be flush, or even very slightly above the rim of the pulley.

Tension should be such that it can be depressed just under 1/2" in the middle of the run.



Nicholas Farr23/03/2020 11:44:27
2962 forum posts
1335 photos

Hi, a guide for belt tensioning can be found on page 76 of Section 3 plenty more information here too.

Regards Nick.

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