Inertia of Alternators vs Generators

[Danny Joe]

I was just wondering if there is a big difference in rotational inertia between alternators and generators. If alternators have less, would that help belt life, especially in engines that are driven hard?

[bbodie52]

The rotating mass of the generator might be slightly heavier than the alternator, which would reduce the "flywheel effect" of the spinning charging system if the alternator was lighter, as it resists changes in engine speed at the crankshaft. Those stresses have to be handled by the fan belt. The greatest improvement, however, was the redesign to the cooling fan implemented by Chevrolet engineers in 1964, when they switched to the lightweight magnesium fan design.

[66vairguy]

The biggest problem is folks over tighten the fan belt. Properly adjusted the belt allows the the gen/alt pulley to slip on overrun. The only time I've seen an inertial issue is with a guy that was racing his Vair and shifting at 7,000+ RPM - not something any stock Corvair engine should ever do.

[Danny Joe]

Yeah, one of the first things I did was install an Otto spring tensioner. My original was junk, about to come apart.

[Jerry Whitt]

I just weighed and armature and a rotor.

Bathroom scale shows both at 5 lbs.

Postal scale showed both at just over the postal scale limit of 5 lbs.

[lostsoul]

sorry but whats a otto spring tensioner pics please im new still

[Danny Joe]

If you are familiar with Clark's Corvair Parts, they are on Page 15. The standard belt tensioner is fixed, you adjust it when the belt is installed and you have to re-adjust it as the belt wears. As the engine RPMs increase, that increases the load on the belt. The Otto tensioner uses a spring and different mounting hardware to allow the tensioner to maintain the proper belt tension at different RPMs automatically.

[Danny Joe]

Sorry, I had to figure out how to copy and post the page from Clark's Corvair Parts.

[66vairguy]

I forgot to mention that the preferred Corvair fan belt is narrower than the standard automotive "V" belt. Most FLAPS (friendly local auto parts store) sell the belt that is too wide as that's what shows up on the "puter". The wider belt has a reputation for causing problems.

The knowledgeable Corvair guys recommend a GATES HC-3V-560 (called a 3V-560 in other brands). The FLAPS and gates site show a #6597 for the Corvair WHICH IS NOT CORRECT!

Clark's also sells the correct fan belt.

A few others have noted that their fan belt problems were caused by the fan pulley being at the incorrect height because the fan bearing was not installed at the correct height in the cover. One fellow turned this into a real experiment and found that just +/- 1/8" off the correct height caused his fan belt to come off frequently.

[66CorsaConv]

I just don't rev it up like I did when I was 17. I had converted my 64 Monza convertable to alternator and every now and then the belt jumped. I still carry a spare in the 66 Corsa.

[Danny Joe]

lostsoul (love your username, by the way!)
If you go through all the posts in this forum you won't be lost anymore. If a subject hasn't been covered here (with pictures and links and recommendations), all you have to do is ask.
I checked the page of Clark's, realized that it did not actually show it in use (Clark's does use a lot of illustrations, but that one wasn't covered.). I took a picture of mine for you.