Alternative Alternator Options

[planedick]

Main bearings

I wonder what effect this will have on bearing loads etc.

[3Phase]

Nice one, T.C.!

You know, there sure are a lot of washers on the bolt holding the pulley to the rotor and the rotor to the end of the crankshaft but I see you've already tested it at high RPM.

I revved the engine up to 7500 rpm, and the belt and pulley spun just fine!!

The 'Op-Yop' in action



Have fun but be careful!

The Psychedelic OP-YOP Returns From Extinction

[XS1100 Newbie]

I wonder also what the rating would be for speed on that pulley? I think the fastest speed it is going to turn under normal motor use is 3650 RPM'S. For sure they aren't balanced very well for speeds above that. Anyone have a dynamic balancing machine? Just kidding about that one, but just a thought on the pulley.

[petejw]

I wonder what effect this will have on bearing loads etc.

i dont think it would be a problem, it would be a similar set up
as a harmonic balancer on an early model cars engine with the alternator
attached by a fan belt, a good indication would be keeping an eye out
on the crank shaft oil seal near the rotor, if that starts to leak then it could be causing unneccesary stress, if it doesnt leak then it should be sweet.
having the pulley closer to the case would probably be better, but tc explained earlier why it wasnt practical for him to do so.
time and milage will tell i guess.

again nice work TC.

[3Phase]

If the new left/right preload on the crankshaft is 'neutral' and the belt is not too tight then everything should be fine.

LONG TERM (a.k.a. "stating the obvious"): the XS engine was not designed for end-loads like most car or truck engines with fifty pulleys and four-and-twenty fan belts. There is no index key for the alternator rotor and the XS primary chain taps power from the center of the crankshaft. In a stock XS/XJ engine only the #4 upper main bearing shell is a thrust bearing.

Main bearing and crankshaft journal/shoulder wear will depend on crankshaft left/right preload and how much tension is required to keep the new belt up tight, out of sight and in the groove.

If the belt is too tight then the the #5 and #4 main bearings and crankshaft journals will wear.

If the crankshaft is 'pulled' to the left or to the right then the #4 upper thrust bearing shell and the thrust bearing face on the crankshaft will wear.

If the belt is too tight and preloads the crankshaft to the left or to the right it will do both, probably before the oil seal fails and starts to leak.

[planedick]

Like 3-phase said: "If the belt is too tight then the the #5 and #4 main bearings and crankshaft journals will wear. If the belt is too tight and preloads the crankshaft to the left or to the right it will do both, probably before the oil seal fails and starts to leak."

And one must remember the higher load in amps results in a higher side load on the main bearing, in addition to the extra horsepower required to drive it. Those kind of bearings must "float" on a film of oil and placing a constant side load in one position will cause premature failure.

[crazy steve]

I don't think the side load on the crank is going to be an issuse; that 10mm bolt that holds the pulley on will probably prove to be the weak point. That was/is my concern about this conversion. When that bolt lets go, now you have no charging system (and nothing holding the OEM rotor on either except for the taper fit).

A 3/8" diameter shaft is awful small for this amount of side load....

[cywelchjr]

That side load is why it would have been nice if there were a more broad flat belt in the right length that could be used. Those types need far less pressure to provide the needed grip, and would load things far less. This all of course depends on just how much side force is needed to spin the alternator without slipping under load. Depending on the unit, and the fact that it's a one to one rather than the usually two or more to one it may not be a problem anyways.

[natemoen]

I know it was brought up before but a chain would reduce side load more, just would need to find a chain that can spin at 10 grand.

[3Phase]

I think T.C.'s done it right and I have a Toyota alternator that looks like it might be just the ticket for my XS.

1)It looks cool!

2) It works!

3) He's still able to post so it's still working!


The cast pulley from Grainger's isn't made to handle a torque load through its axis, it's supposed to slip over the end of a shaft and be held in place with the set screw. It might crack and split but it should be okay if it's centered and not overtightened.

The washer stack and taper-fit rotor is a little worrying but in the pictures the pulleys do look like they're aligned and true and the bolt and washers seem to be genuine Grade 8 or better, not El Queso Supremos.


High-speed chains are noisy as you-know-what and they need oil baths or lots of grease and regular TLC. There is no way you're going to safely mount the equivalent of an external cam or primary chain to an alternator unless you want to spend a lot of time and money to fab it and a lot more time and money making sure you and the new chain continue to look fab.

If a belt goes out you might get some nasty whip marks and rubber bits in places you would rather not, maybe a cut pants cuff or scuffed boot but if a chain goes out it can get really ugly really quickly.

Again: Nice job, T.C.!

[cywelchjr]

I wonder (I just now thought of this) if we could find a short enough toothed belt and pulleys to use for this. It would lower the crank loading even more, and completely prevent slippage as well. Something like a shorter, narrower version of the primary belt used on a lot of the v-twins. I'm not sure if something like that is even available, but might it be worth considering and checking to see if it is?

[crazy steve]

I wonder (I just now thought of this) if we could find a short enough toothed belt and pulleys to use for this. It would lower the crank loading even more, and completely prevent slippage as well. Something like a shorter, narrower version of the primary belt used on a lot of the v-twins. I'm not sure if something like that is even available, but might it be worth considering and checking to see if it is?

Those are out there Cy (pretty common in NASCAR, some other racing bodies), but the cost! The belts aren't too bad (but still much more expensive) but the pulleys are outrageous. Just one of those would cost more than the rest of the swap put together...

For me, the solution would be to attach the alt pulley to the rotor. Either by welding it on, or machining some sort of adaptor that transfers the 'locating' of the pulley to the rotor.

[cywelchjr]

Those are out there Cy (pretty common in NASCAR, some other racing bodies), but the cost! The belts aren't too bad (but still much more expensive) but the pulleys are outrageous. Just one of those would cost more than the rest of the swap put together...

For me, the solution would be to attach the alt pulley to the rotor. Either by welding it on, or machining some sort of adaptor that transfers the 'locating' of the pulley to the rotor.

Ok, I just took a quick look. Don't know about the belt prices, but the pulleys I found were mostly under $10 each in single quantity. Didn't know on the belts cause I wasn't sure how to figure out the length needed or how to figure out how long a given belt is. Where I found stuff was http://www.econobelt.com. Took me less than 5 minutes of looking, so that might not even be the best deals out there since I didn't spend much time on it.

[crazy steve]

Ok, I just took a quick look. Don't know about the belt prices, but the pulleys I found were mostly under $10 each in single quantity. Didn't know on the belts cause I wasn't sure how to figure out the length needed or how to figure out how long a given belt is. Where I found stuff was http://www.econobelt.com. Took me less than 5 minutes of looking, so that might not even be the best deals out there since I didn't spend much time on it.

Interesting.... The automotive types I've looked at were horribly priced. But seeing how these aren't automotive parts, the next thing you'd have to check is hp/rpm rating. Very few electric motors turn faster than 3600 rpm...

[cywelchjr]

Interesting.... The automotive types I've looked at were horribly priced. But seeing how these aren't automotive parts, the next thing you'd have to check is hp/rpm rating. Very few electric motors turn faster than 3600 rpm...

While that is true, neither is the one already chosen for this project. As well, while the motor usually doesn't run faster than 3600, in a lot of cases the driven item does, by using a large pulley on the motor and a small one on the driven item. Balance is generally not RPM based, so its either balanced or not, so it's a matter of it having the structural integrity to handle the centripetal force at the higher RPMs we would run them at, roughly 120% say? I'm thinking there's not enough mass there to matter much, and I can't see an aluminum pulley in the size likely to be used not being strong enough.

It's certainly worth looking into IMHO.