Ritchey compact crank problem (chain rubbing)

Booker C. Bense wrote:
_ What little actual research I've found suggests that it's not
cross-chaining that's "BAD", but small rear spockets in
general. I.e. it's just as "BAD" to use the Big/small as
the small/small.

Who the hell told you that?!?

Bill "sounds more like zero actual research" S.

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In article ,
S o r n i wrote:
Booker C. Bense wrote:
_ What little actual research I've found suggests that it's not
cross-chaining that's "BAD", but small rear spockets in
general. I.e. it's just as "BAD" to use the Big/small as
the small/small.

Who the hell told you that?!?


_ There was a study done by James Spicer, M.E. Prof at John
Hopkins and his grad students. It's in Vol. 123, December 2001
of the Transactions of the ASME. The title is

"Effects of Frictional Loss on Bicycle Chain Drive Efficiency."

_ It pretty clearly states that common chainline angles have no
significant effect on the frictional energy loss. The only factor
that they found increases the friction loss in the drive train is
small sprocket size and low chain tension. The article clearly
states that 52/21 is more efficient than 52/11. A quote from the
article

"It was found that chain line offset and chain lubrication
have neglible effect on efficiency under laboratory conditions."

_ I'm making the perhaps incorrect assumption that if you don't
lose any energy to friction, then you aren't significantly
wearing the chain. The conclusion about lubrication is
particularly interesting, their conjecture is that the primary
purpose of chain lube is as a sealant to keep dirt and water
out of the chain.

_ Booker C. Bense


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On Wed, 25 Aug 2004 23:08:09 +0000 (UTC), Booker C. Bense
. stanford.edu
wrote:

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In article ,
S o r n i wrote:
Booker C. Bense wrote:
_ What little actual research I've found suggests that it's not
cross-chaining that's "BAD", but small rear spockets in
general. I.e. it's just as "BAD" to use the Big/small as
the small/small.

Who the hell told you that?!?


_ There was a study done by James Spicer, M.E. Prof at John
Hopkins and his grad students. It's in Vol. 123, December 2001
of the Transactions of the ASME. The title is

"Effects of Frictional Loss on Bicycle Chain Drive Efficiency."

_ It pretty clearly states that common chainline angles have no
significant effect on the frictional energy loss. The only factor
that they found increases the friction loss in the drive train is
small sprocket size and low chain tension. The article clearly
states that 52/21 is more efficient than 52/11. A quote from the
article

"It was found that chain line offset and chain lubrication
have neglible effect on efficiency under laboratory conditions."

_ I'm making the perhaps incorrect assumption that if you don't
lose any energy to friction, then you aren't significantly
wearing the chain. The conclusion about lubrication is
particularly interesting, their conjecture is that the primary
purpose of chain lube is as a sealant to keep dirt and water
out of the chain.

_ Booker C. Bense

Dear Booker,

Maybe the chain angle causes problems?

Since the chain doesn't mate squarely with the gear teeth,
maybe pressures and wear are concentrated on the edges
instead of across the faces?

And perhaps the sideways flex of the chain opens it up for
more grit to enter?

Even when aligned, smaller gears may wear faster than larger
gears because fewer teeth are cranking the chain at a
sharper angle. On the big-front/small-rear, the 11-tooth
wears out long before the 53-tooth.

It would be nice if someone worked out (or gave general
guidelines) for the average force per tooth for speeds and
pressures. A small-front/big-rear, for example, puts very
little strain on things idling along on level pavement at 10
mph, but things change if the rider is using the same gear
combination to struggle up a steep slope.

I seem to recall Richard Feynmann writing that before he
went to New Mexico, he spent a little time working out the
best gear ratios for the war effort, but never improved on
the advice that he was given on his first day: pick the two
largest gears that give the ratio that you want.

Carl Fogel

wrote in message Dear Booker,

Maybe the chain angle causes problems?

Since the chain doesn't mate squarely with the gear teeth,
maybe pressures and wear are concentrated on the edges
instead of across the faces?

And perhaps the sideways flex of the chain opens it up for
more grit to enter?

Even when aligned, smaller gears may wear faster than larger
gears because fewer teeth are cranking the chain at a
sharper angle. On the big-front/small-rear, the 11-tooth
wears out long before the 53-tooth.

It would be nice if someone worked out (or gave general
guidelines) for the average force per tooth for speeds and
pressures. A small-front/big-rear, for example, puts very
little strain on things idling along on level pavement at 10
mph, but things change if the rider is using the same gear
combination to struggle up a steep slope.

I seem to recall Richard Feynmann writing that before he
went to New Mexico, he spent a little time working out the
best gear ratios for the war effort, but never improved on
the advice that he was given on his first day: pick the two
largest gears that give the ratio that you want.


Some years back I did work out bearing pressure within the chain to find out
whether it would be advantageous to use high pressure gearbox oil. Cannot
recall how many tons/sq inch but was not sufficient to make gear oil
advantageous. From an engineers handbook of a century ago it was suggested
that sprocket sizes be above 17 teeth for minimal chain and sprocket wear.
This is likely to be counting block and link for each tooth, so is the
equivalent of 34 teeth on a bicycle sprocket. Some divergence of chain was
also accounted for. So using the largest available sprocket sizes seems
appropriate for minimal wear.

Trevor

Booker C. Bense wrote:

...
_ There was a study done by James Spicer, M.E. Prof at John
Hopkins and his grad students. It's in Vol. 123, December 2001
of the Transactions of the ASME. The title is

"Effects of Frictional Loss on Bicycle Chain Drive Efficiency."

_ It pretty clearly states that common chainline angles have no
significant effect on the frictional energy loss. The only factor
that they found increases the friction loss in the drive train is
small sprocket size and low chain tension. The article clearly
states that 52/21 is more efficient than 52/11. A quote from the
article...

Take another look at Spicer's data. Spicer et al used constant POWER
input and RPM for the front chainring. Therefore the rear wheel
rotational velocity varied in Spicer's tests depending on which rear cog
was used. Therefore, Spicer was measuring efficiency at the equivalent
different bicycle speeds.

If Spicer's data is rearranged for constant rear wheel rotational
velocity and constant power, the 11T sprocket was the MOST efficient and
the 21T the LEAST efficient at low chain tensions, with efficiencies
converging at higher chain tensions.

Note: the above is a summary of an article by John C. Walton in Human
Power No. 51, Fall 2000.

--
Tom Sherman

Trevor Jeffrey wrote:
wrote in message Dear Booker,

Maybe the chain angle causes problems?

Since the chain doesn't mate squarely with the gear teeth,
maybe pressures and wear are concentrated on the edges
instead of across the faces?

And perhaps the sideways flex of the chain opens it up for
more grit to enter?

Even when aligned, smaller gears may wear faster than larger
gears because fewer teeth are cranking the chain at a
sharper angle. On the big-front/small-rear, the 11-tooth
wears out long before the 53-tooth.

It would be nice if someone worked out (or gave general
guidelines) for the average force per tooth for speeds and
pressures. A small-front/big-rear, for example, puts very
little strain on things idling along on level pavement at 10
mph, but things change if the rider is using the same gear
combination to struggle up a steep slope.

I seem to recall Richard Feynmann writing that before he
went to New Mexico, he spent a little time working out the
best gear ratios for the war effort, but never improved on
the advice that he was given on his first day: pick the two
largest gears that give the ratio that you want.



Some years back I did work out bearing pressure within the chain to find out
whether it would be advantageous to use high pressure gearbox oil. Cannot
recall how many tons/sq inch but was not sufficient to make gear oil
advantageous. From an engineers handbook of a century ago it was suggested
that sprocket sizes be above 17 teeth for minimal chain and sprocket wear.
This is likely to be counting block and link for each tooth, so is the
equivalent of 34 teeth on a bicycle sprocket. Some divergence of chain was
also accounted for. So using the largest available sprocket sizes seems
appropriate for minimal wear.

As usual Trevor, you are disremembering (or more likely,
just making things up). The recommendation from the
engineers handbook for not using a sprocket less then 17
teeth is to minimize chordal action, not to minimize wear.
In fact, the handbook recommends using a sprocket of no
greater than 67 teeth to minimize chain wear. Here is the
excerpt from the handbook:

http://www.sdp-si.com/D757/pdf/D757P478.pdf


Mark McMaster

Capt- That's a _very_ good analogy. I may steal it BRBR

Feel free-thanks for the refferal, BTW-

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

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In article ,
wrote:
On Wed, 25 Aug 2004 23:08:09 +0000 (UTC), Booker C. Bense
.stanford.edu
wrote:


Dear Booker,

Maybe the chain angle causes problems?


_ Maybe, I've never noticed it though. If some
one could state exactly what angle is "bad" vs
good, I might give it more credance. But 30 years ago
when there were only 5 gears, longer chainstays
and 120mm rear hubs, the same advice was
given. If those shallower angles were "bad", then
pretty much every gear but the middle three are
"bad" on current 130mm hubs and 41 cm chainstays.

_ I used to follow this advice, but at one point I broke my front
derailler and being a poor grad student I just took the derailler
off and rode the bike in the lower chainring all the time. On
flat ground I was constantly in small/small. I was just using a
bike as transportation then and did little to no maintance on
it. I road it this way for about 2K miles over 2 years, almost
all of it in small/small. Just for fun I checked the old
chain from this bike and it's still within wear limits. It had
at least 3k miles on it before the derailler broke.
The freewheel looks fine with the crud taken off. So I'm
pretty flummoxed as to what I was wearing out before it's
time.

_ Since then I've pretty much used whatever gear seems convient
at the time and I don't go through chains faster than anybody
else. Maybe it's just my beautifully efficient pedaling style %-),
but I doubt it.

_ Booker C. Bense





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In article ,
wrote:
On Wed, 25 Aug 2004 23:08:09 +0000 (UTC), Booker C. Bense
.stanford.edu
wrote:


Dear Booker,

Maybe the chain angle causes problems?


_ Maybe, I've never noticed it though. If some
one could state exactly what angle is "bad" vs
good, I might give it more credance. But 30 years ago
when there were only 5 gears, longer chainstays
and 120mm rear hubs, the same advice was
given. If those shallower angles were "bad", then
pretty much every gear but the middle three are
"bad" on current 130mm hubs and 41 cm chainstays.

_ I used to follow this advice, but at one point I broke my front
derailler and being a poor grad student I just took the derailler
off and rode the bike in the lower chainring all the time. On
flat ground I was constantly in small/small. I was just using a
bike as transportation then and did little to no maintance on
it. I road it this way for about 2K miles over 2 years, almost
all of it in small/small. Just for fun I checked the old
chain from this bike and it's still within wear limits. It had
at least 3k miles on it before the derailler broke.
The freewheel looks fine with the crud taken off. So I'm
pretty flummoxed as to what I was wearing out before it's
time.

_ Since then I've pretty much used whatever gear seems convient
at the time and I don't go through chains faster than anybody
else. Maybe it's just my beautifully efficient pedaling style %-),
but I doubt it.

_ Booker C. Bense





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Mark McMaster wrote in message ...
Trevor Jeffrey wrote:
wrote in message Dear Booker,

Maybe the chain angle causes problems?

Since the chain doesn't mate squarely with the gear teeth,
maybe pressures and wear are concentrated on the edges
instead of across the faces?

And perhaps the sideways flex of the chain opens it up for
more grit to enter?

Even when aligned, smaller gears may wear faster than larger
gears because fewer teeth are cranking the chain at a
sharper angle. On the big-front/small-rear, the 11-tooth
wears out long before the 53-tooth.

It would be nice if someone worked out (or gave general
guidelines) for the average force per tooth for speeds and
pressures. A small-front/big-rear, for example, puts very
little strain on things idling along on level pavement at 10
mph, but things change if the rider is using the same gear
combination to struggle up a steep slope.

I seem to recall Richard Feynmann writing that before he
went to New Mexico, he spent a little time working out the
best gear ratios for the war effort, but never improved on
the advice that he was given on his first day: pick the two
largest gears that give the ratio that you want.



Some years back I did work out bearing pressure within the chain to find
out
whether it would be advantageous to use high pressure gearbox oil.
Cannot
recall how many tons/sq inch but was not sufficient to make gear oil
advantageous. From an engineers handbook of a century ago it was
suggested
that sprocket sizes be above 17 teeth for minimal chain and sprocket
wear.
This is likely to be counting block and link for each tooth, so is the
equivalent of 34 teeth on a bicycle sprocket. Some divergence of chain
was
also accounted for. So using the largest available sprocket sizes seems
appropriate for minimal wear.

As usual Trevor, you are disremembering (or more likely,
just making things up). The recommendation from the
engineers handbook for not using a sprocket less then 17
teeth is to minimize chordal action, not to minimize wear.
In fact, the handbook recommends using a sprocket of no
greater than 67 teeth to minimize chain wear. Here is the
excerpt from the handbook:

http://www.sdp-si.com/D757/pdf/D757P478.pdf

I know not which you refer to, the handbook in my possession is dated 1897
and is clear in its advice.

Trevor