Help! Dual V Belt alignment issue.

[darylat8750]

Hello All,

I picked up a Delco 28 SI 160AMP alternator in perfect condition with a 2G 1/2X3 1/8X.875 pulley. My Ford/Lehman 2715E has a crank shaft damper with two 1/2" grooves. I have a water pump pulley that matches the belt spacing of the damper. The flat between the v grooves is 7/16" and the center to center of the v grooves is 15/16" on both. The distance between the water pump and alternator pulleys is roughly 14" and from alternator to crank shaft is a little more. With the new mounting brackets the 28 SI will be mounted slightly higher and will have just a little more belt rap.

The issue: I can't find a pulley for the alternator with this groove spacing.
I have included a picture of the pulley that I have been able to source with the v grooves too close together. If the alignment is perfect (and it will be very, very close) the misalignment will be about 1/8" on each belt. Is this much miss alignment within parameters? It seems like a lot to me. I'm assuming that if I install the alternator with the current pulley it will eat the belts. Care to guess how many hours I would get on the belts before they are just dust in my engine room?

Does anyone know of a source of 2G 1/2x2 1/2 15/16 (or 1/2") x .875 pulley? A 2 1/2" diameter would be perfect but a 3" diameter would work fine. The .875 bore has to be exact.

click on the picture to expand

Regards,
Daryl

[Dsanduril]

I would try Motion Industries if you haven't already. This item seems to match:

https://www.motionindustries.com/pro...p?sku=03133418

The total face width is 1 3/4", which matches your tape measure, but the picture makes it look like the groove spacing is slightly different, I'd call them and see if they can provide a drawing.

If not there I'd try TB Woods, but digging through all their catalogs is a pain, easier to just make a call.

[darylat8750]

Thanks for the response.

I haven't tried them and I will call them tomorrow morning.

The alum. one has the spacing I'm trying to match. The steel anodized one has the v grooves too close.

[Dsanduril]

Yeah, I figured from the tape that was the case. All the pulleys I looked at just gave an outside-outside face dimension, and yours shows 1-3/4", but most of the pictures look like even spacing rather than the wider spacing on your alloy sheave.

Another possible option, see if a pair of single groove sheaves are narrow enough that you could build a little custom spacer/shim to put between them to make up to the proper spacing. Never tried it, but can't see why it wouldn't work if you can secure both properly to the shaft.

[darylat8750]

2 singles back to back may work. I'll look into that.

" can't see why it wouldn't work if you can secure both properly to the shaft."

Amazingly enough they aren't keyed or even locked to the shaft with a set screw. What turns the alternator is the friction between the back of the pulley and the face of the rotor.

[kjdavie01]

Have to admit that if it were me, I'd install the one you have and see what happens. I've seen belts under heavy load (15hp ventilation fans) with gross misalignment (8-10 degrees!) run for weeks before finally shredding. Much to my surprise!
The 1/8" misalignment you describe - over a distance of 14" or so, gives a very small ANGULAR offset - and it's that angle that matters. If your pulleys were only 4-5" inches apart, I'd not try it, but belts aren't like chains or gears, they are flexible to a limited extent - I bet it would run for quite a while.

[darylat8750]

Thanks for your input. I've run some farm equipment that was far worse than this also. I am tempted to just try it but I have a lead on a solution that will give me the correct alignment. I keep telling myself to do it right so I only have to do it once. Also I have to drain the coolant in order to change the belts which is time consuming and messy. It is a power boat and I've put over a thousand hours on it in less than two years and plan on using it a lot over the next two years.

[abelungu]

Any machine shop can make it no problem


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[darylat8750]

Thanks.
I'm going to talk to a local machine shop tomorrow. It will be simple with a lathe. It doesn't even need a keyway cut.

[rwidman]

If you change the outside diameter won't that throw off the tach?

[darylat8750]

Originally Posted by rwidman

If you change the outside diameter won't that throw off the tach?

Yes it will. However if I don't spin it faster than the old alt. I wouldn't get full electrical output at my normal cruise rpm. Also my tach has an adjustment for different number of pulses per revolution and I hope to find one that is at least close. I have a good quality hand held tach that I can use to calibrate the system.

[Terra Nova]

Don't Mickey Mouse it. Buy or fabricate a proper pulley.

[darylat8750]

Originally Posted by Terra Nova

Don't Mickey Mouse it. Buy or fabricate a proper pulley.

Agreed.

I actually found one this afternoon that has everything right except the bore is too small. I think that to buy that, have it shipped here and bore it out will be about the same cost as to have one made from bar stock. I will find out in the next couple of days.

Thanks everybody for your support.

[Terra Nova]

Re-boring is much simpler and relatively foolproof.

[abelungu]

Reboring is not a good idea, if it's cast. If its stock? why be messing around have one made. Oversize a little so it run faster. Alternators burn because of not enough ventilation most of the time. Leave room for the best fan you can get on there.



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