SpiwakD@aol.com wrote:
> Amici
>
> Has everyone given up on improved rear hubs? It seems that the latest
> fix is for new axles. Is there an improvement to hubs which has not been
> tried yet? Was the failure of newer alloy hubs due to a thin area which
> cannot be redesigned or the type of alloy? I know a shop willing to take the
> challenge, but I do not want to repeat past mistakes or lessons learned.
> Dave
Jeff Snook is really the proper person to respond to this question, but I don't
know where in the world he is (literally) at the moment so I'll respond with my
observations, which, as usual, may be suspect:
1. Jeff's hubs were made from 4140 steel, not heat treated, certainly an
improvement over the original stuff.
2. This design eliminated the little weep hole from the grease dribble
retaining
ring on the back of the hub. Many hubs had failed with the fatigue crack
starting
at this little weep hole. The grease retaining ring was also eliminated, which
gave the opportunity to put a good machined finish on the radius without the
rough machining marks that I see in all the stock hubs.
3. The hub diameter at the seal was increased and a new seal supplied. I think
that the designer chose the largest hub diameter that he could and still allow a
commercially available seal to be used.
4. Some problems were encountered with these hubs, some of which in my humble
opinion were unwittingly initiated by owners (hope no one is too offended). It
was found that if the axle nut was tightened to significantly higher torques
than
the factory manual (like 150 - 200 lb ft) then the hub would swell and crawl up
the axle. Not too surprising in light of the very gradual taper. Secondly, some
folks who lapped in the axles ended up with them bell-mouthed and unusable.
Third, several people, myself included, noticed upon disassembly after short use
that there was a different surface appearance between the outer 2/3 and the
inner
1/3 of the tapered portion of the axle. This worried some folks enough that they
decided to not use the hubs.
I think the above is all factual data. Now comes my editorial comment, for
however little it is worth.
If you could cross-section an axle / hub assembly, you would see that the flange
to which the wheel is bolted is directly outside the location of the end of the
axle keyway. Guess what? What has always been happening to these things that
none
of us ever tumbled to is that the axle flange keeps the hub from bell-mouthing
under side load, but the hub is free to bell mouth inboard of the flange since
the seal diameter is all that resists. This explains the difference in surface
appearance, because there was relative motion between the hub and axle inboard
of
the end of the keyway. And, wouldn't you know it, the bending occurred right at
the end of the keyway, an ideal location from which a fatigue crack would
eminate.
Hope you're not sorry you asked............
--
TR6 -- 29 and still running
TR4 -- 39 and being rebuilt
uncle jack -- down but not out
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