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Ideas on why Alternator belt is shredding?

S

SW EM

Member
Hey all,

I'm posting a picture of an alternator belt that has been self-destructing since I put the alternator on my Farmall MD. The kit came from Steiners, but did not include the belt, so I matched the size used before with the generator.

(Pictures are sideways because my phone was vertical when taking pictures, sorry)

I think the issue is the pulley on the alternator being too wide compared to fan shaft pulley. The belt is lined up pretty good, and I only have maybe 2.5 hours on it.

Has anyone had this issue before? And are different sized pulleys available for these alternators?

Thank you!
a259619.jpg

a259621.jpg

a259622.jpg
 
The shafts on both pulleys have to be parallel with each other and the pulleys have to be in line with each other. It may be the photography but the alternator appears to be crooked being pulled up higher in the back.
 
hard to tell but it looks like the belt is too narrow for the pulley. maybe try a wider belt. look at a metric belt it may be a tad wider, or go to a 5L belt . another option is try one of the power twist belts. they are a linked belt, you add or subtract sections to size them. that is what i am running on my m with a hitachi alternator.
 
I think the belt is too wide. Looks like it is sticking up above the rim of the alternator pulley.Use a belt that fits the pulley of the alternator. The wider pulley on the tractor tractor will take care of itself.the small diameter pulley you have is right. Don't know if a wider pulley is available or not. Go see your NAPA store.But most likely something is not lined up. Or there is a bad rough spot on one of the pulleys.The shredded outer corner looks like it is rubbing on something. Look over everything closely.I've been useoing alternators for 20 years on several H/M etc tractors. Still using the first belt,have never had oe shred like that.
 
Your pulleys are not aligned from looking at your picture. If the belt is not so low in the pulley that it contacts bottom of belt, or so high it rides above pulley ,the width of pulley is not your problem .. If belt is metric, know that the angle on V is different from pulley.
 
I see this a lot, the dirt that gets sucked into the belts from fan draft eats at the pulley till it wears the "V" flat, then the belt is drawn down into the worn "V" and it flairs the outer edges like the one in the picture,,no one normally looks at the pulleys, but on larger tractors with bigger fans it becomes a real problem,, the belts will slip and squeal, so they get tightened up more, then the water pump bearing and the alternator suffer from the extra tension. When I do an engine over haul I look at the pulley wear and change them out if needed, a worn pulley can let an engine over heat, and of course make a water pump bearing fail too soon.
 
Hi, it looks to me the belt is bottoming out on the fan pulley. Put a narrower pulley on the alternator and change the belt to match both. That's my thoughts.
Ed Will Oliver BC
 
Pulleys don't look out of line enough to cause a problem. The belt is a 5/8 width?

You might have a defective belt or a broken water pump pulley. Was a common problem on Farmall tractors.
 
You are correct. Your alternator pulley is wider than your fan pulley. Belt is riding too low in alt pulley and too high in fan pulley. You can get different width pulley's. Any starter/generator shop will have a variety. You'll need an impact to zip the nut off.
 
It's all about alignment and the proper belt.

You can check the alignment with a straight edge across the alt pulley. The straight edge should be perpendicular to the driving pulley. Get that right first, then use the straight edge to get the front to back alignment. Be sure the alignment doesn't change when the belt tension is applied. Look at the pivot bolt hole in the alternator. If it has been run loose in a previous life, the hole may be wallowed allowing the front to tip down.

Look closely at the driving pulley. Be sure it isn't cracked or rough. Also the sides of the pulley should be flat, not worn concave from a slipping belt.

What did that pulley originally drive? Can you look at a factory belt and get the width? With that information you can order a belt the length you need and know it is the right width for the pulley.

Then, compare that belt to the alternator pulley, see if it is the right width and angle.

And, yes there are many different pulleys available for the alternator. Probably the best source would be a starter/alternator repair shop. They probably have every size ever made in the bone pile.

One other thing, from the looks of the failing belt, it looks like something may be touching the back side of the belt, or a broken or bent pulley.
 
Why is the back of the one belt looking all radius like when it should be lying flat ? Squeezed too tight by that pulley ?
 
the alternator pully is too wide as most agree on. it takes some power to run a charging alternator. you have the same problem with yor fan belt. its sitting too low in the pulley. problem wont show up with it as quick because dont take as much effort to run that fan. also get a good quality belt, as the cheapy ones dont last for a job like that.
 
What type of belt? I.e. what angle is is cut? Did you use a FHP belt (fractional horsepower or an automotive belt? Delco stock alternator pulley calls for a 36 degree angle belt. Fractional horsepower belts like a 3L (for 3/8") or 4L (for 1/2") are the wrong V-angle and are 40 degree.
 
Looks like the drive pulley rear flange had the belt outside the flange OD. Does that flange happen to have any damage on it, tearing into that side of the belt?
 
I am waiting to here what belt you chose to use? A FHP belt or an automotive belt?
 
Hello SE EM,

I see the same thing that David G saw. Look at the belt, it is away from the front of the fan pulley, while it if rubbing in the engine side of the pulley. The alternator needs to go forward towards the radiator for a better alignment. A properly sized shim in the back of the alternator pulley should do the trick,

Guido.
 
But, it is cockeyed too, not just for and aft . Like I said before, too wide, too narrow, no problem if not running above or below sides of pulley and pulley is not worn of course. I have seen many belts in pulleys with wrong width and no problem. As example, the water pump on that engine has a variable width pulley to obtain the tension adjustment on the belt. Angle on the face of the belt is also a issues as I also said and someone else said. A belt intended for foreign made cars for example have a different face angle. What degree it is, heck, I do not know, just that it is different and does not work well.
 
Hello pete23,

Yep you are right.! I suspect the pulleys are also part of the problem. He should have them match the belt. Some old school belts rode on top of the groove I have learned the hard way the even if all else is well, just 1/2 in. Off on the length of a fixed adjustment belt system spells failure,

Guido.
 
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