Good of you to mention an alternator tensioner failure. I'm designing an alternator tensioner out of aluminum. Hopefully Paul can take a look at it, and I'll
post a photo of it soon. It's a different design 3/4" inch square tube with .125" walls, used strictly in compression.

Brian Trubee

Alternators are notorious for destroying brackets for some strange reason.
Chrome molly 4130 steel has a fatigue limit while aluminum does not. What that means
is if the stress is below some value a 4130 steel bracket will last for
ever while an aluminum bracket will fail sooner or later. Since the vibration
amplitude and frequency are unknown on an alternator bracket it is risky to
use aluminum. If an aluminum bracket is over designed by a bunch it will probably
last a long time. That is not to say it is not possible to design a weak
steel alternator bracket that can fail. The saving grace about brackets
is they are usually small and weigh less than a pound. So in general over
designing brackets does not add much to the overall firewall forward weight.
For the same reason therefore it is best to make them out of heavier 4130 steel.

This prototype is made from angle iron. Most of the load is on
the pivot bolt closest to the V belt so there needs to be another small
clip added to hold the other end of the alternator. The adjusting strut
was cut down from the stock part.

Paul Lamar

That's got me convinced- I've got some 4130 tubing and will make my adjuster out of that.

Brian Trubee

 
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