Andre Charl writes:

Hello folks. Recently, my American Classic rear hub had a problem.
Those of you familiar with the design will know it's problematic.
To differentiate his design from Shimano \ Campy, Bill Shook decided
to avoid using traditional spring-loaded pawls. The idea here is to
decrease coasting drag friction, as the AC pawls do not drag across
the freehub teeth when coasting. This is great, in theory.

There is a picture of this mechanism on their web site:

http://www.amclassic.com/Road_Hubs.html

However, various escapements have been invented over many years and
the silent pawl used by Regina, SunTour and others has practically no
drag because the large "heel" has enough viscous friction in the body
to not snap back at rotational speeds of interest. That is also why
they cannot be heard.

The problem is that the 6 pawls are engaged through a "pawl plate".
The pawl plate is engaged, amazingly, by a flimsy piece of wire that
is wound around the inside face of the freehub. A couple of
millimeters of the wire are bent in towards the pawl plate. This
portion of the wire is angled obliquely such that it drags against
the pawl plate's engagement holes. When coasting, the familiar
machine gun sound is heard. However, this is not the Shimano \
Campy spring-loaded pawl sound.

Unfortunately there is no picture of this device assembled but it
seems to rely on the drag of the wire on the pawl plate. This being
an unreliable drag, the engagement is equally unreliable. Because it
cannot be heard, the assumption is that there is no drag... but there
is. Besides, the actuator wire slides over the pawl plate across the
series of holes visible in the picture of the parts.

The problem is that it's ill-advised to rely on this flimsy piece of
wire for the critical task of engaging the pawl plate. The bent
portion of wire must be angled perfectly. If it hits the plate too
squarely, then coasting drag is huge; if it hits too shallowly, then
there's a chance it won't engage the pawl plate when pedaling. This
happened to me on a ride, luckily I stopped off at a friend's and
switched out the wheel.

I find amazing how many people do not study history, in mechanics,
politics or warfare. We don' need no steenkin new escapements. See
Hugi, the loudest and most expensive ratchet on hubs with no redeeming
value. Besides these problems, the mechanism is not well protected
against water and dirt.

I have since serviced the hub. Getting that wire to hit the pawl
plate properly is a true nightmare. It's currently set up with the
wire hitting the plate somewhat squarely, in order to ensure
engagement. Sadly, this does result in much more coasting drag than
either Shimano or Campy. Ironically, I'm sure Bill Shook's goal was
to eliminate coasting drag...

Well, Sturmey Archer went through the spring-less pawls on their SW
hubs only to discover they had feet of clay. Riders stood up to pedal
and flew forward in neutral, the pawls not engaging at all because the
oil was more viscous than the inventor had imagined.

Bill, if this is forwarded to you, I would suggest that the next
generation of hub incorporate a much better solution for pawl plate
engagement. Something spring-loaded is a must. Relying on the
modulus of elasticity of a material (bent wire) really is a
shortcoming in this otherwise-elegant design.

Although the pawls do not make contact when coasting, the actuator
wire does and has more drag than typical good pawls.

Jobst Brandt