Thanks, Bob. You are now lint-free.
I'll put you down for one vote that the hubs break due to increased
cornering forces and due to accumulated stresses related to cornering
forces and perhaps by accumulated damage caused by failure of other
bits.
And I DO know of one GT6 which busted hub and axle on his way through
the Kink at Road America -- he was lucky to avoid ending up as a stain
on the new concrete there. I've had my GT6 through there on several
weekends and must admit to doing it at a notch under full-tilt-boogie,
having the hubs in mind.
Scott
> -----Original Message-----
> From: Bob Lang [SMTP:LANG@isis.mit.edu]
> Sent: Wednesday, February 16, 2000 8:36 AM
> To: Barr, Scott
> Cc: 'fot@autox.team.net'
> Subject: Re: The Hub of the Issue
>
> Hi,
>
> I'm not a metalurgist, and I've not been a racer for eons, so my
> offering
> is more along the lines of a "lint picking session"... but to answer
> the principle question: why do hubs break? I'd have to say "for a lot
> of
> reasons".
>
> Have the cornering forces increased? Well, in a word: yes. Think about
> it
> - have lap times changed since these cars used to race?? Yes. _If_ you
>
> can find a track that hasn't changed. But tire compounds are stickier,
>
> suspension settings generally tend to be quite a bit harder than they
> used to be - something's gotta give somewhere.
>
> But wait - there's more. Even when your car can slide, there are
> plenty
> of big forces on your little GT6 hubs... the metal will twist a little
>
> bit each time you stress it. Eventually, you can develop stress cracks
> at
> the surface, and if these pieces are stressed further - they will
> fail.
>
> There's also the bigger problem (at least from my perspective) of
> determining the lineage of your parts. Take for example that pesky hub
>
> that someone heated cherry red to take apart... I can't say with
> authority that such a process doesn't change the temper of the part,
> but
> my best guess is that it has to effect it somehow. If you're lucky,
> you
> get to see the cracks on the surface - if you're not lucky - well then
>
> you'll know how good the part is eventually.
>
> If you want to be sure of the integrity of the parts - get 'em
> x-rayed.
> At the very minimum crack test the parts that get stressed the most on
>
> some sort of regular basis. Your local welding supply store will have
> the
> stuff you need to check for surface cracks.
>
> But basically - things wear out. And when in doubt - replace.
>
> Now, a quote (from memory, so forgive me if I'm slightly off-base
> here)
> from the TR6 competition prep manual suggests replacing the TR6 rear
> hubs
> every _four races_. I'll bet this was suggested because that's how
> many
> races they would see before the all important bearing end-float would
> go
> into the "critical range" and likely fail if run any more, but Kas
> could
> probably provide some insight there. On TR6's, one of the failure
> modes
> is that one of the bearings will spin in place when the bearing
> end-float
> gets excessive, and this will score the axle stub and form a nice
> little
> place for cracks to start. And I further know that Spitfire axles are
> not
> made any more betterer (!) than big Triumphs - so I'll bet bearing
> end-float is real important and more important when they fail (the
> bearing spins, for example) you're wrecking the axles.
>
> The GT6 (and Spitfire) parts - being smaller and lighter, are probably
>
> just as prone to problems if things get "out of whack" regarding
> bearing
> end-float and torque spec and the like.
>
> Bottom line - if you don't want to ball your car up, you need to check
>
> this stuff on a very regular basis.
>
> And do as I say, not as I do. But I'm not a road racer, so a failure
> in my
> persuit would likely be less "life threatening" (well to me anyway,
> apologies in advance to any cone pickers should my car ever suffer an
> axle failure) than a road racer's might be. By way of example - if you
>
> doubt your car would be able to go full tilt through Road America's
> "kink", you're probably not doing enough preventive maintenance to get
>
> your confidence level where it should be.
>
> Hmmm. I'm overly wordy today. Sorry for rambling. X-ray your hubs,
> please.
>
> rml
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