Question for those running a Moss Supercharger...

[swift6]

Have been working on a '69 equipped with a Moss Supercharger set up. It has now destroyed two alternators, traceable to the side load being placed on the alternator from the serpentine belt. Below is a pic and you can see the damage done to the original alternator. The rebuilt alternator lasted about 50 miles before it did the same but that could be a combination of side load and cheap bearings.

Has anyone else experienced this issue with the serpentine belt on the Moss system?

 

[TR3driver]

Friend of mine has a Moss/JK Jackson blower on his Miata. The original idler pulley assembly was defective and allowed the belt to slip under boost. Likely if we had reefed down on the belt tension to stop the slippage, failures like the above would have resulted.

He contacted Moss, who supplied a replacement idler assembly that solved the problem.

I'd also be tempted to convert to the Bosch alternator (from a 78 Ford Fiesta with AC) as they seem to be higher quality than the Lucas units.

 

[TR3driver]

Oh yeah, also check to be sure that the shafts serviced by the serpentine belt are parallel. ISTR we had to shim the blower mounts to get it lined up right.

 

[swift6]

On the TR6 set up, the only thing supplying the tension to the belt is the spring loaded tensioner. Not sure how it would suddenly apply MORE force.

We checked the alignment on everything. Did it a couple of times now just to be sure.

We are thinking of upgrading to a better alternator in order to get better bearings. It ate up the second alternator in 50 miles. I'm sure that was a weak bearing issue. The old Lucas alternator could have just worn to the point it couldn't take it anymore. As you can see in the picture, it ground the bearing into the case. The second alternator didn't do that, the bearing started squealing and the owner stopped before it could do any more damage.

 

[Guest]

Hey Shawn,

This can go in your "For What It's Worth" file, but it MAY be relevant, if not boring.

The first sportscar I was ever exposed to was a friend's MGA in high school in 1960. It had a Judson supercharger on it. The setup included replacing the 2-carb setup with a supercharger and single carb. The setup ran TWO belts.

The bracket on the supercharger was spun aluminum or cast aluminum (whichever the cheap/weak one was). If both belts were tightened properly, the first rev would snap the pulley. This happened to him 2 or 3 times, to where he finally gave up and ran ONE LOOSE BELT. So, in actuality, he was running LESS THAN STOCK.

In hindsight, and without knowing the historical specifics, I would think that this was due to mis-alignment of the pulleys; which you would think would have been obvious at the time.

If alignment is not your problem, then disregard this email, although it may give someone else cause for contemplation.
Bueno suerte/bon chance,

George

P.S. I see that you are in Fort Collins. That is where John Macartney "turned right" after we escorted him to the New Mexico/Colorado border and turned him over to Glenn and the others. Well Done to you guys! And thanks for lunch!!

 

[swift6]

P.S. I see that you are in Fort Collins. That is where John Macartney "turned right" after we escorted him to the New Mexico/Colorado border and turned him over to Glenn and the others. Well Done to you guys! And thanks for lunch!!

Many of us from my local club met John in the summer of 2000, while we were on a club trip to England. I had been corresponding with John via the Triumph List and we set it up so we would tour Gaydon (the BMHIT museum) while he was there and he would be our "tour guide". It was really good to see John again and have a few laughs with him. We showed him some of our local roads, albeit at a brisk pace. Then I led him back south through the traffic nightmare of Fort Collins as he returned to Glenn's house for the evening.

I wasn't able to accompany him out of Colorado heading for Omaha but it was great to see him again anyway.

 

[swift6]

For those interested in what the pulley arrangment of the Moss system looks like, here you go...

 

[TR3driver]

So, from your previous comment, I guess they've added a spring-loaded idler to the belt for the alternator. Seems kind of odd, given that it's still mounted to the factory tension adjustment, but ... how much force the idler spring applies to the alternator bearings is going to depend substantially on belt angle and hence where the factory adjustment is positioned. If you can slide the alternator closer (or even use the next-longer belt), it will reduce the side load on the alternator bearings.

 

[swift6]

The alternator is adjusted in as far as it can physically go and the next longest belt is 6" longer.

The spring loaded tensioner is on the left (facing the engine) and below the waterpump. The pulley on the right of the waterpump is an idler with no adjustment.

 

[TR3driver]

My mistake; looked like two belts to me. After downloading and tweaking your photo, I see that it's only one. Please ignore my comment, only solution I see is alternator bearings that are up to the tension from the spring loaded idler.

Unless you could somehow back off the spring tension a bit (which might lead to belt slip under some conditions).

And I'm assuming you've watching this thing working over various rpms, to see that there aren't any strange vibrations or whatnot.

 

[swift6]

Yeah we have watched through various rpms. No wiggle, no slip etc... We are looking into sourcing a version of one of the many alternator conversions that was originally designed for serpentine belt use. Thinking that those bearings might be more up to the task.

On the standard rebuilds, it doesn't inspire much confidence when you ask the people at the parts counter for a specific alternator and the first thing they ask is if its a warranty issue.