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Old 17-05-2022, 14:07   #1
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Alternator Belt Dust

Having fitted a Balmar 100A alternator to my Volvo MD22L I'm having a significant issue with belt dust despite derating it to about 70A with the belt load manager. The belt is a 9.5mm cogged V belt, and I fitted an unused but old Volvo belt. The alternator is a single foot alternator and the foot is just 1" long which doesn't give it much lateral stability so the belt tension seems to pulling it slightly out of alignment so the alternator axis is no longer parallel to the crank shaft. The resulting misalignment is 1-2mm over the 25cm belt span. How best to fix the issue without spending over £500 on a serpentine belt kit?

What brand of belt would you recommend? I've heard Gates recommended. Any others readily available in the UK?

The crank pulley and water pump pulley are both 10mm but the alternator pulley is 13mm, I've heard of people using a 13mm belt in that situation. which apparently works even though it sits proud of the smaller pulleys. Any experience with that or advice on whether to use a 10 or 13mm belt?

There seem to be 2 different cogged v belt sections that are both about 10mm, XPZ, or 3V/3VX. What's the difference and which should I be using? And likewise for 13mm belts there's XPA or AX.

What's the best way to sort out the misalignment of the alternator shaft? I was thinking I'd see if I can shim the alternator mounting bracket where it bolts to the block, but not sure if that will be possible. Any other ideas?

Do I even need to do anything about that? How much misalignment of the belt is acceptable?

I was also considering fitting a belt tensioner like the Balmar Belt Buddy. Are then any other better or cheaper options.

Thanks, Bruce
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Old 17-05-2022, 18:03   #2
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Re: Alternator Belt Dust

At 100 amps, you really need a serpentine belt. We have a 110 amp, and made the switch. Engine compartment is way cleaner now.
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Old 17-05-2022, 18:32   #3
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Re: Alternator Belt Dust

You need to derate till dust is minimum. Doesnt reall6 matte4 want the loading chart says unless you ate ok with the dust/ breaking a belt.
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Old 18-05-2022, 07:55   #4
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Re: Alternator Belt Dust

With some allowance for transmission losses and rounding-off the numbers, 100 amps is ~2hp.
A couple of charts I looked at suggest that a 3V belt should easily handle that load.
It appears that your alternator has a good "wrap".
I wonder if the profiles of the engine pulleys and the alternator pulley are fully compatible, you certainly don't want the belt to be riding on the bottom of a pully groove.
A 1>2mm lateral misalignment seems pretty minimal over that span, I would be more concerned with angular misalignment.
As you go thru the rpm range at load, can you get someone to watch the "actions" of the belt, i.e., is their some range where the belt starts to flutter/shake?
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Old 18-05-2022, 08:00   #5
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Re: Alternator Belt Dust

This may help

https://marinehowto.com/marine-alternator-installation-tips-tricks/
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Old 18-05-2022, 08:16   #6
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Re: Alternator Belt Dust

Quote:
Originally Posted by bstreep View Post
At 100 amps, you really need a serpentine belt. We have a 110 amp, and made the switch. Engine compartment is way cleaner now.
THIS - you can fight the issue all you want but to Resolve/fix it the serpentine belt is absolutely the answer. To not go down this path from the get go is a penny wise pound foolish journey. I wasted way to much time and a bit of money trying to “fix”.

I have played this game before - tried multiple solutions. The serpentine belt eliminated dust, decreased noise and vibration, and allowed proper higher output settings of alternator.

One of the most satisfying fix’s upgrades I ever made to a boat.
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Old 18-05-2022, 08:57   #7
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Re: Alternator Belt Dust

Quote:
Originally Posted by Brucekav View Post
Having fitted a Balmar 100A alternator to my Volvo MD22L I'm having a significant issue with belt dust despite derating it to about 70A with the belt load manager. The belt is a 9.5mm cogged V belt, and I fitted an unused but old Volvo belt. The alternator is a single foot alternator and the foot is just 1" long which doesn't give it much lateral stability so the belt tension seems to pulling it slightly out of alignment so the alternator axis is no longer parallel to the crank shaft. The resulting misalignment is 1-2mm over the 25cm belt span. How best to fix the issue without spending over £500 on a serpentine belt kit?

What brand of belt would you recommend? I've heard Gates recommended. Any others readily available in the UK?

The crank pulley and water pump pulley are both 10mm but the alternator pulley is 13mm, I've heard of people using a 13mm belt in that situation. which apparently works even though it sits proud of the smaller pulleys. Any experience with that or advice on whether to use a 10 or 13mm belt?

There seem to be 2 different cogged v belt sections that are both about 10mm, XPZ, or 3V/3VX. What's the difference and which should I be using? And likewise for 13mm belts there's XPA or AX.

What's the best way to sort out the misalignment of the alternator shaft? I was thinking I'd see if I can shim the alternator mounting bracket where it bolts to the block, but not sure if that will be possible. Any other ideas?

Do I even need to do anything about that? How much misalignment of the belt is acceptable?

I was also considering fitting a belt tensioner like the Balmar Belt Buddy. Are then any other better or cheaper options.

Thanks, Bruce

A couple of things going on that isn't helping belt wear.

1. Alignment and bracket. The bracket may be too flimsy for that size alt. and the alt. adjustment is all the way to the end of the bracket. The alt. torque is too much for that bracket and would make another beefier bracket. A slightly shorter belt to get the alt. more mid-range in the adjustment in the bracket slot may also help. When the alt. is engaged the pulleys need to stay fairly well in alignment.

2. Proper pulley size on the alt. If you are trying to use a 9.5mm belt in a 13mm pulley it will slip all day no matter how much you tighten it. Change the alt. pulley to 10mm to match the crank/water pump pulleys. (if you try a 13mm in a 10mm pulley it will ride too high). A proper width belt should ride in the groove more like this:


We run a Dayco Topcog Gold belt on our 90amp alt. and there is minimal dust.
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