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Old 02-16-2017, 03:19 PM   #1
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twin Alternator Belts Uneven Wear

I have a Sabreline 36 with twin CAT 3116. On both engines there are two belts going to the alternator. After about 100hours one of them has elongated more than the other. It is worse (but only just) on the S/B engine.

CAT recommend changing the two belts at the same time. Seems a bit wasteful to me. Does anyone have a solution or can recommend a way of correcting this?
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Old 02-16-2017, 03:29 PM   #2
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I think when you buy belts you can asked for a matched set ( mfg in same batch ) . I want to say they have a batch number stamped on them.
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Old 02-16-2017, 03:37 PM   #3
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Yes, buy the belts as matched pairs. I am surprised that Cat sells singles.

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Old 02-16-2017, 04:05 PM   #4
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I have been using CAT belts that are sold as matched pair. Still have the problem!
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Old 02-16-2017, 04:47 PM   #5
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Double check alignment of the pulleys. If axes of shafts are not precisely parallel, there will be unequal tension in the belts and they will wear differently. Also if pulleys are worn or machined differently.

I have grown to dislike multi belt systems. In some troublesome instances, it is best to take one of the two out and just run a single belt. Whether that is an option depends on how much load is on the alt.
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Old 02-16-2017, 05:03 PM   #6
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Greetings,
Might an option be to replace the two with one flat belt or is that what Mr. Ski is suggesting? I suppose it would mean replacing all the pulleys but over time cost of double v-belt replacements would possibly be worth it.
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Old 02-16-2017, 05:09 PM   #7
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I would be inclined to believe there is a problem such as Ski suggests. I mean this can't be normal for all of these can it? If all else fails you could try a "common back" or more properly called "banded belts". All you need is the size of the current belts, the comman back belts are available at Some industrial supply houses.

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Old 02-17-2017, 10:14 AM   #8
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Quote:
Originally Posted by gilbertpark View Post
I have a Sabreline 36 with twin CAT 3116. On both engines there are two belts going to the alternator. After about 100hours one of them has elongated more than the other. It is worse (but only just) on the S/B engine.

CAT recommend changing the two belts at the same time. Seems a bit wasteful to me. Does anyone have a solution or can recommend a way of correcting this?
Well, you could swap the two belts after 100 hours and see what happens.

I don't think anything as drastic as switching to a different kind of belt (with different pulleys) is called for. Perhaps you could contact the manufacturer and see if they have a solution or if this is a common problem with engines like yours.
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Old 02-17-2017, 10:41 AM   #9
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The problem with double belts is if there is ANY difference in geometry, not only will the belts wear unevenly, they will fight each other. Their ratios will be slightly different.

Try running a single belt. Easier than trying to figure out the geometry issue. Lots of 31 series Cats have only one alt belt.
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Old 02-17-2017, 11:21 AM   #10
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I think the load on the belt(s) is what determines if one or multiple belts are needed. They wouldn't have installed two if one was sufficient.
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Old 02-17-2017, 11:39 AM   #11
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I think the load on the belt(s) is what determines if one or multiple belts are needed. They wouldn't have installed two if one was sufficient.
A fair assumption to make. But I have seen the same engine with same alt, one with single belt and one with double.

It would have to be a pretty high output alt to actually need double belts. Maybe that's what he's got??
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