I don't get where this is going
We've started from a Shimano (steel) freehub failure, and now it comes that alluminium alloys are not suitable for bicycle manufacturing because "no fatigue life" (sentence that sound like an absolute statement) ?
We're comparing oranges to apples here, as clearly my
"weight like per like". Of course, alluminium alloys are not suitable for applications where space is a constraint and a lot of shear force is exerted
has not been considered. This shows how a discussion can be manipulated to provide only one's user opinion. Not exactly what Forums are for, exchange of opinions.
Anyway, let's cool off. I'll try to give a more useful contribution to the OP with this faulty Shimano 780 freehub that came into my hands right yesteday.
I've been lucky to be allowed the use of a proper workshop. The hub has been quickly laced to an old rim with old spokes, for easy removal of the jammed freehub.
The freehub would rotate only by a few degrees, and won't move even with strong force applied.
Once opened, the upper race looked okay. I'm not sure if one of the ball-bearings is missing?
No real contamination to be seen, but that pawl is not coming up, not good
Wow, the inside of the freehub has deep marks on the ratchet ring
Think I've found the culprit.
That piece of pawl is supposed to be down in the pocket and attached to the pawl, to get the pawl spring acting on it
Here it is, broken
And the opposite one too
It looks like the design can be improved, the pawls have a tab where the spring acts on.
The freehub core has 4 pawls, and two springs. Each spring acts on two pawls only, I assume this is to due to space constraint, as the spring(s) won't be able to act on 4 pawls at the same time.
It is no surprise that most of the 4-pawls freehubs designs I've seen, they use a spring per each pawl.
But I'm not engineer, so this is only my view on it. It could be just a batch of faulty material, wrong hardening of the pawls, or else.
Having a few friends in club rides that do use Ultegra 6800 hubs (similar to this) with no issues even after many long rides and Audax in all weather, I think they've sorted the issue?