Most of the Friction In A Bicycle Chain

[I've tried to reformat the table from MEB's post so _I_ can
understand them; I don't guarantee this is correct but it looks
sensible to me. YMMV]

meb writes:

Here's a summary of results, percentage
efficiency values estimated from the graphs printed in Radmarkt. New,
clean, lubricated chain drives

1-spd 3-spd Hub Gear 6-spd Derailleur
Power Low 1:1 High 24T 19T 13T
50W 96.0 90.6 93.4 87.3 94.2 94.1 92.1
100W 97.3 92.8 95.7 90.9 96.2 96.4 94.9
200W 98.1 94.0 96.9 92.9 97.4 97.6 96.9
400W 99.0 95.0 97.9 93.9 98.1 98.4 97.8

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; 99% of browsers can't run ActiveX controls. Unfortunately
;; 99% of users are using the 1% of browsers that can...
[seen on /. 08:04:02]

I have reformated since Simon had even more problems than I did with the
efficiencies.

“ Measurements of Efficiency of Chain and Shaft Drives Section 1.2.2
Contributed by Chris Juden, CTC Technical Officer, .
The best work I know of on this subject was commissioned by Fichtel &
Sachs AG. Comparisons of single-speed, multi-speed hub and derailleur
gearing were published in Radmarkt Nr.12/1983 and I am aware of other
work within that company which compared the efficiency of chains in
various states of neglect. Here's a summary of results, percentage
efficiency values estimated from the graphs printed in Radmarkt. New,
clean, lubricated chain drives


_______1-spd____3-spd Hub Gear____6-spd Derailleur Power___________Low
1:1 _High_____24T 19T 13T 50W____96.0_____90.6 93.4 87.3_____94.2 94.1
92.1 100W___97.3_____92.8 95.7 90.9_____96.2 96.4 94.9
200W___98.1_____94.0 96.9 92.9_____97.4 97.6 96.9 400W___99.0_____95.0
97.9 93.9_____98.1 98.4 97.8


Used chain (8000km), no rust, lubricated 100W 94-96%, 200W 97-98%
Neglected used chain (7000km), rusty, dry 100W 88%, 200W 93% We can draw
some interesting conclusions from these data. They confirm that hub
gears are a little less efficient than derailleur, even in direct drive,
and show that they work better in low than high ratio. With a
derailleur: running the chain around the little pulleys takes only about
1W. And a misaligned chain is much less wasteful than small sizes of the
sprocket, especially at low power levels. Indeed: at 50W the out of line
24T does a bit better than the in line 19T! 13T is not even very small
by today's standards, but is clearly rather inefficient. At very high
power levels however, alignment may become as important as size.”


Two related issues: With larger sprockets, you’re distributing the load
over more teeth making it less likely you’ll sheer teeth off or wear
them out as quickly. Worn sprocket teeth will wear out chains faster,
and if extreme enough, wear out chainrings. The downside, the extra
weight of the chainrings, chain, and sprockets.

Does anybody have any idea where the tradeoff on weight vs. efficiency
is? There may be differing optimal weight/efficiency points based upon
the size and strength of the rider. A large strong rider might tend
toward the heavier more efficient combination. A lighter rider might
find the weight is more significant than a few hundredths of a percent
efficiency improvement.



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meb in
Message-id: writes:

.. . .

Does anybody have any idea where the tradeoff on weight vs. efficiency
is?

You mean *overall* efficiency vs drive train
efficiency.

It depends on terrain but it can be
precisely calculated for flat land at certain
speeds:

Assume that the drive efficiency
improvement results in a 15% increase in
drive weight and drive wt. is 15% of bicycle
wt. and bicycle wt. is 15% of total weight
and that rolling resistance is 20% of total
power consumption because, let's face it,
the 800 pound gorilla is wind resistance.

That's about 0.07% decrease in *overall*
efficiency on flat land.

If your improvement doesn't cost too much
and results in more than 7/100th percent
increase in drive efficiency, you might want
to try it.

Obviously this calculation has been done
by others long before any of us were alive
because bicycle design ain't an accident.
Smart guys like Orville have been looking
at bicycles for decades.


Bret Cahill

my oil bath residue of 3 grams silica removed from the chain gives 3-4
hi gears over the "dirt chain." on a 14 speed.

my oil bath residue of 3 grams silica removed from the chain gives 3-4
hi gears over the "dirt chain." on a 14 speed.

meb wrote:

Does anybody have any idea where the tradeoff on weight vs. efficiency
is?

Yes, people have their own. For instance instead of 53x11 I go for 57
X 12.
This also gives a slightyl more compressed gear range for racing,
there being plenty to go at these days.


There may be differing optimal weight/efficiency points based upon
the size and strength of the rider.

I'd be more interested in any aero disadvantage of the larger ring in
normal cicumstances.

Andrew Bradley

meb wrote:

Does anybody have any idea where the tradeoff on weight vs. efficiency
is?

Yes, people have their own. For instance instead of 53x11 I go for 57
X 12.
This also gives a slightyl more compressed gear range for racing,
there being plenty to go at these days.


There may be differing optimal weight/efficiency points based upon
the size and strength of the rider.

I'd be more interested in any aero disadvantage of the larger ring in
normal cicumstances.

Andrew Bradley

wrote:

Pl/Ptot = (0.22)(1/20 + 1/20) = 2.2%

for 40/40

Pl/Ptot = (0.22)(1/40 + 1/40) = 1.1%

Something doesn't work here!

Looks OK to me, since articulation losses are inversely proportional
to sprocket size, half the size means twice the loss, what doesn't
work?

That's the point. By having large chainwheels with 50+ teeth, they
are practically out of the picture as they obscure the losses at the
other end. We should be looking at the losses in small sprockets. By
always changing both CW and SPKT's the linear relationship of
efficiency to sprocket size is lost. The 20 - 20 and 40 - 40 example
demonstrates that.



For some reason much posting on this topic tends to get confused (and
I don't disclude my own). Which all goes very well with the reporting
of test results on the net.

Here's a post intended to clear up some confusion that has been
created but which could well fail.

As regards the simple model under discussion, whether you consider
just sprocket or sprocket-and-ring the situation is still linear, all
that changes is the constant.

Raw data from a fixed chainring-size test will have small sprockets
coming out looking (slightly) better than they should.

Why? Because riders can't be expected to vary their gear to suit the
drivetrain. In given conditions a rider wants a given gear, so in
useful data, when sprocket changes so does ring.

Surprisingly, one report, reportedly based on the Spicer data, showed
small sprockets as more efficient in fixed chainring and bike speed
conditions, but again no detail on methods available.


Andrew Bradley

wrote:

Pl/Ptot = (0.22)(1/20 + 1/20) = 2.2%

for 40/40

Pl/Ptot = (0.22)(1/40 + 1/40) = 1.1%

Something doesn't work here!

Looks OK to me, since articulation losses are inversely proportional
to sprocket size, half the size means twice the loss, what doesn't
work?

That's the point. By having large chainwheels with 50+ teeth, they
are practically out of the picture as they obscure the losses at the
other end. We should be looking at the losses in small sprockets. By
always changing both CW and SPKT's the linear relationship of
efficiency to sprocket size is lost. The 20 - 20 and 40 - 40 example
demonstrates that.



For some reason much posting on this topic tends to get confused (and
I don't disclude my own). Which all goes very well with the reporting
of test results on the net.

Here's a post intended to clear up some confusion that has been
created but which could well fail.

As regards the simple model under discussion, whether you consider
just sprocket or sprocket-and-ring the situation is still linear, all
that changes is the constant.

Raw data from a fixed chainring-size test will have small sprockets
coming out looking (slightly) better than they should.

Why? Because riders can't be expected to vary their gear to suit the
drivetrain. In given conditions a rider wants a given gear, so in
useful data, when sprocket changes so does ring.

Surprisingly, one report, reportedly based on the Spicer data, showed
small sprockets as more efficient in fixed chainring and bike speed
conditions, but again no detail on methods available.


Andrew Bradley

(g.daniels) wrote in message . com...
Andrew Bradley?

who supplies the 57?

TA

Andrew Bradley