On 12/15/2018 1:30 PM, Emanuel Berg wrote:
AMuzi wrote:

For braking, pad size is a minor factor.
It's all swept area, CF and leverage.
You're right that linkage is efficient but
the leverage is minimal and rubber on chromed
steel has a low CF, made worse by dried
hard pads.

OK, so now it got complicated...

Swept area, should that be big or small for the
brake to be efficient? Small, right? As in disc
brakes where say a single degree of braking on
the small disc translates to a much larger
distance on the big wheel?

Or are disc brakes more efficient because of
material interaction and other technology
improvements alone?

And if the linkage on rod brakes is efficient,
how can leverage be minimal unless there is
something wrong with the levers, and they seem
pretty straightforward to me? Or is it the
shackle that is pulled onto the rim, as opposed
to squeezed into/around it, which is
more efficient?

Also, CF, is that some material
interaction property?

Emanuel, with all due respect, you should spend the winter reading a
physics book or two. Or three. Skip the parts on electricity, atomic
physics, etc. Concentrate on forces, motion, work, energy etc. - the
parts that apply to bicycles.

I say that because words like "efficient" have carefully defined
technical meanings, and you tend to mis-apply them. "Leverage" is
perhaps less technical, but probably better expressed as "mechanical
advantage." And look up "swept area" for brakes (you can google it). By
CF, Andrew meant Coefficient of Friction. It's most often abbreviated
with the Greek letter "mu" which is hard to type into these discussions.

Really, you need more foundation in basic mechanics and physics. It will
allow you to understand the relevant mechanisms and to phrase your
questions much more clearly. This study will be well worth your time,
and will save the rest of us time as well.

--
- Frank Krygowski