Re: Anyone try a Torker giraffe yet? why so cheap?

johnfoss wrote:
> *The 'experience' is to have the sprocket unscrew. Track bikes are
> only pedaled in one direction. On a unicycle, we use all our strength
> to change directions all the time. Threaded-on sprockets can be a
> lawsuit in the making... *

This isn't exactly true.  Speed regulation for trackies is virtually
identical to unicycle balancing.  

Unscrewing a sprocket on a track bike at speed is at least as bad as
falling from a giraffe.  Probably worse.  You're pretty high up when you
are on the bank, and all that kinetic energy has to go somewhere.  Also
you're cleated down so there's no escaping the bike.  

And trackies aren't weak - most of the elite sprinters can push at least
400-500 lbs with either foot.  I can think of several races where I was
getting boxed in and needed to suddenly move back by a wheel length or
two to make my escape.  I used full force to resist the pedal movement,
which meant that I was using a source of energy more powerful than my
legs. 

There are two kinds of track hubs with lockrings.  The first, and
DEFINATELY UNSAFE version has both the cog and the lockring threaded in
the same direction on the same set of threads.  This system is sometimes
used on street fixed gears where the rider has brakes, so John's
assumption is valid.  No amount of lock-tite or tightening will keep
this kind on the hub if the rider aggressively backpedals.  It's ok for
mild speed modulation, but I'd never ride one.

The other kind, which is the only type approved for track use.  The hub
has two sets of threads - a larger diameter one threaded in the normal
way so that the cog tightens against the hub when pedaling forward. 
Just outboard of this set of threads the hub diameter decreases and a
second set of threads is cut which tightens in the opposite direction. 
The lockring mounts on this second set of threads

The way to secure this setup is to first get the cog as tight as
possible (a couple of spirited accelerations usually does the trick),
then use a C-spanner to jamb the lockring against the cog.  If the cog
tries to unscrew it tightens the lockring further. After a few good
sprints the lockring is tightened even further.  No lock-tite required.


So, I don't know what method Torker uses, but I assume for safety sake
it's at least a real track hub properly installed.  If it's not, if they
are using the poor-man's lockring, then I definately agree with John
that it's unsafe.


--
cyberbellum - Level 0.5 rider

If I knew what I was doing I wouldn't be in research...
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