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American Classic hub design problem



 
 
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  #1  
Old November 12th 04, 09:55 PM
Andre
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Default American Classic hub design problem

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.

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.

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 pedalling. This happened to me on a ride,
luckily I stopped off at a friend's and switched out the wheel.

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...

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.

Thanks.

--
--------------------------
Andre Charlebois
AGC-PC support
http://agc-pc.tripod.com
BPE, MCSE4.0, CNA, A+


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  #2  
Old November 13th 04, 12:12 AM
external usenet poster
 
Posts: n/a
Default

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

  #4  
Old November 13th 04, 08:11 AM
external usenet poster
 
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Default

David Newman writes:

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.


Are any currently-available hubs equipped with the silent pawl you
describe? If so, which ones? Up to now, I've found Shimano to be
quieter than the other hubs with which I'm familiar, but if there's
a hub even quieter than that, I'd like to know about it. I am
appalled by noisy hubs like Chris King, which sounds to me something
like a swarm of angry bees.


I haven't disassembled a Shimano hub so I don't know what they use.
The problem with ratchets arose when freehubs reduced the operating
diameter of the ratchet and at the same time MTB's began using less
than 20t on chainrings with as much as a 1:2 ratio... four times any
gears that were encountered with previous freewheels. With Pawl
failure, most designs went to what they considered failsafe, using
double or triple engagement and unusual pawls.

In freewheels with ball bearings, that invariably are not perfectly
adjusted, eccentric rotation is probable and in that case only one
pawl carries the entire load. This is something engineers of the past
were aware of and therefopre never attempted multiple engagements.
Regina for instance had two pawls 180 degrees apart and 21 ratchet
teeth to give fine 42 engagements per rotation.

Campagnolo made an aluminum freewheel that didn't work even though
they thought they had triple engagement (of three pawls). Since they
were singly carrying the entire load at some point, they went into
yield under high pedaling torque. Hugi used the face spline that has
all teeth engaged at once but these also suffer from slightest
eccentricity that is inherent even elastically with the chain pull as
great as occurs at maximum torque.

As far as I could see, superficially, Shimano bit the bullet and made
their single pawls wide enough to hold the load one at a time. I
think their large size makes them noisier than classic freewheels.
Take one apart and see if there are an even or odd number of teeth in
the ratchet and the number of pawls.

Jobst Brandt

  #6  
Old November 13th 04, 10:26 AM
Phil, Squid-in-Training
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Default



Are any currently-available hubs equipped with the silent pawl you
describe? If so, which ones? Up to now, I've found Shimano to be quieter
than the other hubs with which I'm familiar, but if there's a hub even
quieter than that, I'd like to know about it. I am appalled by noisy
hubs like Chris King, which sounds to me something like a swarm of angry
bees.


Old LX silent clutch hubs are still available.

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

They are also available through J&B distributors.

--
Phil, Squid-in-Training



  #7  
Old November 13th 04, 11:51 AM
B
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Posts: n/a
Default

I am appalled by noisy
hubs like Chris King, which sounds to me something like a swarm of angry
bees.


I have 2 CK rear hubs.One is as you describe. The other is no noisier than a DA
hub, and not nearly as noisy as a Campy hub (tested while riding alongside
someone with a Campy hub). I have no idea what makes my 2 hubs different. The
quietest rear hub I have is an Ultegra.
B

(remove clothes to reply)
  #8  
Old November 13th 04, 03:51 PM
Weisse Luft
external usenet poster
 
Posts: n/a
Default


Andre Wrote:
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.

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.

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 pedalling. This happened to me on a ride,
luckily I stopped off at a friend's and switched out the wheel.

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...

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.

Thanks.

--
--------------------------
Andre Charlebois
AGC-PC support
http://agc-pc.tripod.com
BPE, MCSE4.0, CNA, A+


I have a 2001 model and it has a 24 tooth, low flange freehub. The
three pieces of wire that drive the pawl engagement plate are plunger
spring loaded, not cantilever sprung as you describe. I have had no
problems with it, other than shedding grease after lubrication. Here
is the image from AC:

[image: http://www.amclassic.com/Hub-Tech/Im...igure_08S.jpg]
(strip the stuff in brackets for regular newsreaders)

I know these three detents are plunger loaded because I have pushed
each one in during my last grease-change service. Since I have older
versions with grease ports, I needed to do this after changing from
Finish Line to Phil Wood grease as the two are rather non-compatable.
Wood is a far superior grease for these hubs but when mixed with Finish
Line, the mix is runny like 90W axle lube and creeps out of the seals.

I noticed a bit of wear on these plungers since the pawl cam plate is
made from spring temper sheet and is a bit harder. There is an
abundance of plunger length and the wear is limited to the corner of
the plungers.


--
Weisse Luft

  #9  
Old November 13th 04, 05:19 PM
Andre
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Posts: n/a
Default

Strangely, my freehub does not appear to resemble any of the four described
on the website. All four on the website seem to utilize the spring-loaded
pins, as you describe, Weisse. Mine, as I mentioned, simply uses a piece of
bent wire that drags against the pawl plate.

American Classic, please clarify this situation. Is there a hub available
that has spring-loaded engagement pins? I would ask that some manner of
replacement solution be implemented.

--
--------------------------
Andre Charlebois
AGC-PC support
http://agc-pc.tripod.com
BPE, MCSE4.0, CNA, A+

"Weisse Luft" wrote in
message ...

Andre Wrote:
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.

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.

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 pedalling. This happened to me on a ride,
luckily I stopped off at a friend's and switched out the wheel.

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...

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.

Thanks.

--
--------------------------
Andre Charlebois
AGC-PC support
http://agc-pc.tripod.com
BPE, MCSE4.0, CNA, A+


I have a 2001 model and it has a 24 tooth, low flange freehub. The
three pieces of wire that drive the pawl engagement plate are plunger
spring loaded, not cantilever sprung as you describe. I have had no
problems with it, other than shedding grease after lubrication. Here
is the image from AC:

[image: http://www.amclassic.com/Hub-Tech/Im...igure_08S.jpg]
(strip the stuff in brackets for regular newsreaders)

I know these three detents are plunger loaded because I have pushed
each one in during my last grease-change service. Since I have older
versions with grease ports, I needed to do this after changing from
Finish Line to Phil Wood grease as the two are rather non-compatable.
Wood is a far superior grease for these hubs but when mixed with Finish
Line, the mix is runny like 90W axle lube and creeps out of the seals.

I noticed a bit of wear on these plungers since the pawl cam plate is
made from spring temper sheet and is a bit harder. There is an
abundance of plunger length and the wear is limited to the corner of
the plungers.


--
Weisse Luft



  #10  
Old November 13th 04, 05:47 PM
Dave Thompson
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Posts: n/a
Default

Andre wrote:
Strangely, my freehub does not appear to resemble any of the four
described on the website. All four on the website seem to utilize
the spring-loaded pins, as you describe, Weisse. Mine, as I
mentioned, simply uses a piece of bent wire that drags against the
pawl plate.

American Classic, please clarify this situation. Is there a hub
available that has spring-loaded engagement pins? I would ask that
some manner of replacement solution be implemented.


Have you queried American Classic directly?
1-800-813-5545


 




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