Frank A. said:* I've got two Hunters and a third on the way. They are
great frames and as far as bowing at the brake bosses,
my MUni's set up with Maguras are capable of stopping
the wheel with way more power than I will ever use or
need. *
I suppose I should weigh in here as I'm having Rick build
me a frame with a link between the fork blades at the
brake boss.
Why did I request this? Braking power was never a
consideration, nor was strength of the frame a concern. When
the brakes are applied they push in on the rim which bows
out the frame, however the frame bow is very small compared
to the travel of the brake so it really has no effect on
braking force. All it does is cause the lever to feel a bit
spongey, which isn't all that bad in my experience because
it can make it easier to judge how much force you are
applying at the rim. And since the bowing is almost
certainly below the elastic limit the frame won't take a
permanent set. (At least, not from just braking. Hitting a
truck while braking might cause some permanent
deformations...)
The rim applies a traction force to the brake (and vice
versa) that also causes the fork to bow slightly, however
this is also negligable unless the brake sticks and unsticks
which could, theoretically, cause a vibration at low speeds.
I wasn't too worried about this either because the effect
can't really happen at any speed where I would want to use
the brake.
However, since the traction and inward forces are applied
off-axis with respect to the fork they also apply a twisting
force (a torque) to the fork. This is the effect that I was
worried about. "Worry" is really too strong a word here;
clearly people have brakes on Hunters that work, so perhaps
"curious" is a better word.
This twisting force causes a slight misalignment of the
shoe against the rim. A twist of even one or two degrees
dramatically changes the pattern of pressure between the
brake pad and the rim. If the brake shoes are perfectly
aligned with zero brake pressure, then when forces are
applied the shoes twist out of alignment, which
dramatically reduces the force, so the shoes spring back
into alignment, the forces build up again and the cycle
repeats. This is what causes the infamous "brake squeal" on
poorly aligned bicycles.
Savey bike mechanics "toe in" the brake shoes so that
applying the brake brings the shoes into perfect alignment
to maximize the braking effect and eliminate the squeal. On
some bikes I had to toe the brakes in as much as 5 to 7
degrees to get the bike to stop squealing.
Now, on my Hunter Coker will I ever apply the brakes hard
enough to make them squeal? Doubtful. However, I'm a belts
AND suspenders kind of guy. The fork stays are so long, and
the tubing so narrow that I figured there was a possibility
of squeal, and also figured that the brakes would be more
predictable if I did something to control the alignment of
the pads. (Note that a "brake booster" does exactly the
same thing - control twist - but from the other end of the
brake bosses.)
Was I REALLY worried about predictability and brake squeal?
No, not very much. This extra tube radically stiffens the
fork tube against torsion, and it's not that big a deal to
add, so I figured it would be cheap insurance.
Did I think it would be cool to have a unique Hunter?
Yeah, a bit.
Did I think it would help other Unicyclists to recognize my
oddball Coker if it ever got stolen? Definately!
--
cyberbellum - Level 1.0 rider!
Optimists think the glass is half full. Pesimists think the glass is
half empty. Engineers think the glass is too big.
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