What is the angle on a V belt pulley?

[Ultradog MN]

After 9 years of running my tractor with no wiring harness and just charging the battery once in a while I've finally gotten around to converting it to an alternator, making it charge and even start with the key.
Imagine the convenience...
So I bought a reman Delco 10-SI alternator yesterday.
The pulley on it is too narrow for the fan belt but it is made of cast iron with plenty of meat there to widen the groove on the lathe.
I just did a cursory search but didn't find the angle of the sides of the groove.
Does anyone have that angle stored in the far back recesses of their brain?
Thanks

 

[Eyerelief]

This help?

 

[francist]

Note that the angles on the pulley grooves are not necessarily the same as the angle on the belt sides. There are factors such as the sheave diameter which can causes the belt to squish into a slightly different shape as it passes around the pulley so the pulley sides will often have different sidewall angles to reflect that. How critical is it for your application? Only you can decide that, but here’s a link that shows a bit more about it.

https://www.masterdrives.com/engineering/groove%20dimensions.pdf

-frank

 

[Jake M]

The angle of the belt changes when it bends around the pulley. If you didn't specify otherwise, it probably came set up for a 4L belt. What belt are you hoping to run on that pulley? B, or 5L? It's not much, but they're different. In theory your angle is gonna be accurate to something like a third of a degree or less. In practice they seldom are made that exact.

What's the diameter of the pulley (just measured at the outside). What belt are you going to be using? If it's a B or 5L then something between 30 or 31 degrees would probably get you going just fine. It's gonna be off the charts though as it's on the small side for that belt. If I'm mistaken and you're stepping up to an A belt, or 4L, it might be as much as 32 degrees.

How much load is this gonna see? If (and I'm guessing....), it's been nine years without a wire harness, you're talking about a diesel engine and you only want to replenish the battery after an engine start... At that low load, something that looks about right might do the trick. If you're going to put any tangible wattage on this (bad battery, additional lighting, gas engine ignition systems, and whatever else you think of with your newly discovered electricity factory), it matters more. The pulley will work fine under more load even if it's wrong, but belt life will suffer .

 

[Ultradog MN]

The angle of the belt changes when it bends around the pulley. If you didn't specify otherwise, it probably came set up for a 4L belt. What belt are you hoping to run on that pulley? B, or 5L? It's not much, but they're different. In theory your angle is gonna be accurate to something like a third of a degree or less. In practice they seldom are made that exact.

What's the diameter of the pulley (just measured at the outside). What belt are you going to be using? If it's a B or 5L then something between 30 or 31 degrees would probably get you going just fine. It's gonna be off the charts though as it's on the small side for that belt. If I'm mistaken and you're stepping up to an A belt, or 4L, it might be as much as 32 degrees.

How much load is this gonna see? If (and I'm guessing....), it's been nine years without a wire harness, you're talking about a diesel engine and you only want to replenish the battery after an engine start... At that low load, something that looks about right might do the trick. If you're going to put any tangible wattage on this (bad battery, additional lighting, gas engine ignition systems, and whatever else you think of with your newly discovered electricity factory), it matters more. The pulley will work fine under more load even if it's wrong, but belt life will suffer .

I appreciate the help from you guys but I was hoping for a simpler answer.
I pressed the pulley onto a mandrel and used a dial indicator. Kept adjusting the angle on the compound till I got close to 0 as I followed the angle on the pulley.
It is real close to 20 degrees.
@Jake M
Yes it is a diesel. If I parked it on a hill to roll start it I wouldn't need a battery at all
Other than oil changes I haven't touched it for 9 years.
But it needed some love - rear axle seals, brakes, charging system, steering adjustment, etc, etc.
It ain't pretty but it's really a little sweet heart.

 

[K30]

10SI is a good and simple (cheap!) alternator, but the 12SI has a little better cooling. You can get a screen for the rear side of them that will keep grass etc from getting pulled through it if you're going to mow with it.

 

[Provincial]

If the alternator pulley is so small that the belt has trouble wrapping around it, try a cogged version. For the B size (standard on old Ford tractors) use a BX belt.

I have 10SI alternators on my Ford 2N and 8N tractors, as well as my CJ2A Jeep. All work great. A good auto electric rebuild shop will have a B pulley in stock.

 

[Jake M]

I like those tractors.... Nothing that fits into my life unfortunately, but I like em.

If you indicated almost 20 degrees, that's almost 40 included. That's a straight belt section, not curved. That ain't right......

Like I said though, if you're not working the belt hard on that pulley, it'll probably be fine. That's how they get away with selling stuff like that..... And you're right, finding the absolute correct angle for any given application does get a bit "sciencey", and at some point you really do reach a point of diminishing returns.

Good luck with that old toy old tractor. If I had more room.......

 

[Ultradog MN]

After 9 years of running my tractor with no wiring harness and just charging the battery once in a while I've finally gotten around to converting it to an alternator, making it charge and even start with the key.
Imagine the convenience...
So I bought a reman Delco 10-SI alternator yesterday.
The pulley on it is too narrow for the fan belt but it is made of cast iron with plenty of meat there to widen the groove on the lathe.
I just did a cursory search but didn't find the angle of the sides of the groove.
Does anyone have that angle stored in the far back recesses of their brain?
Thanks

Thanks fellas.
Though I do strive for good to excellent, I was never one who needed to do perfection.
This alternator is only 35 amp and will only charge the battery so I doubt if it will ever see the kinds of loads that require exact specs on the pully.
I just finished making the new brackets for it.
@Provincial,
Nice to see another Ford owner.
I started with a 2N that my father gave me when he passed 23 years ago.. It ran good so I never had to do much to it. Had a lot of fun and did a lot of useful work with it. Then sold it and bought an 8N and then a couple of Hundred Series and finally a bunch of 3 cylinder Thousands. Fixed them, sold them, parted them out, etc.
25 or 30 Fords later I still have three of them.
Are you a member of any of the tractor forums?
I belong to Yesterday's Tractors and a couple others. Same screen name everywhere I go.

 

[Gnpenning]

If I'm not mistaken 10si had a brush holder for diesels that is different from gas motors thanks to the vibration. With that said any 10si will work, just not as long. They are super easy to rebuild.