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Main
Date: 21 Jun 2007 03:56:58
From: Johan Bornman
Subject: Bike Chain Efficiency Study
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I came across this study on the efficiency of a bicycle drivetrain.
http://www.jhu.edu/news_info/news/home99/aug99/bike.html
In some ways I think academia is naive. Then again, this link points
not to the research paper but the Press Release and we all know that
PR is, well, PR.
The way I see this study is thus:
Approaching this experiment from the infra-red angle has been done
before in at least one study I've seen. This one correspondes with the
wide range of efficiency in the other study as well, ranging from
1%-19%.. One Percent loss is probably for a perfectly lined-up chain
going from biggest to biggest sprocket, a situation not possible on
real world bikes where cross-chaining will eliminate some of the
efficiency. 18 Percent energy loss is likely to be from Granny Gear to
11tooth sprocket in a heavily cross-chained situation. They don't say.
I doubt that those researchers "found" that sprocket size matters. It
is common knowledge and hardly needs a PhD student to find it. Perhaps
I should go and do my PhD there.
As for their finding that lubrication does not affect
efficiency....the real issue is wear, not efficiency in my view. Clean
polished steel operating in clean conditions like a lab will perform
well without lubrication, especially at low speeds experienced by
bicycle chains. On the road, even a tarred road, it is different. Grit
will quickly get in there and spoil the party.
As for lubrication being a seal. I don't think so. I have seen how
easily grit and road dirt mixes with lubrication. I don't for a minute
believe that lubrication "takes up space that would otherwise have
been taken up by dirt". It transports dirt to the inside. Even wax
transports dirt to the inside. That's easy to demonstrate.Oil is not
as superflous as they seem to make out
God forbid that bicycle manufacturers start advertising the energy
efficiency of their drivechains. Already we have to put up with the
nonsense of energy efficiency in pedals which have a low stack heigh
with the cleat, and all "stiffer" bumph, imagine if we now have to put
up with 98% fat-free type rubbish on marketing hype as well.
Finally, if they (the researchers) think that chains have not evolved
in the last 100 years, they haven't seen Carl Fogel's pictures.
One thing I can't understand is their claim that tension decreases
friction. Anyone have any views on this?
Johan Bornman
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Date: 25 Jun 2007 05:44:49
From: Luns Tee
Subject: Re: Bike Chain Efficiency Study
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In article <1182423418.361997.41270@w5g2000hsg.googlegroups.com >,
Johan Bornman <coldbeer@telkomsa.net > wrote:
>One thing I can't understand is their claim that tension decreases
>friction. Anyone have any views on this?
I don't see where they claim it decreases friction. There's a
difference between improving efficiency and reducing friction.
If I pay $10 in shipping to receive $1 worth of goods, that's
inefficient. The same $10 service charge for $100 worth of merchandise
is a more efficient transaction, though the service charge didn't decrease.
There's a certain amount of power lost in the slack run of the
chain as chain leaves the rear cluster, goes through the rear derailleur
and wraps onto the front chainwheel. This loss depends on the tension of
the bottom run, which is governed by the derailleur's tensioner, and is
independent of the work being transmitted by (the tension of) the top
run of chain.
-Luns
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Date: 21 Jun 2007 10:39:53
From:
Subject: Re: Bike Chain Efficiency Study
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On Thu, 21 Jun 2007 03:56:58 -0700, Johan Bornman
<coldbeer@telkomsa.net > wrote:
>I came across this study on the efficiency of a bicycle drivetrain.
>
>
> http://www.jhu.edu/news_info/news/home99/aug99/bike.html
>
>In some ways I think academia is naive. Then again, this link points
>not to the research paper but the Press Release and we all know that
>PR is, well, PR.
>
>
>The way I see this study is thus:
>
>Approaching this experiment from the infra-red angle has been done
>before in at least one study I've seen. This one correspondes with the
>wide range of efficiency in the other study as well, ranging from
>1%-19%.. One Percent loss is probably for a perfectly lined-up chain
>going from biggest to biggest sprocket, a situation not possible on
>real world bikes where cross-chaining will eliminate some of the
>efficiency. 18 Percent energy loss is likely to be from Granny Gear to
>11tooth sprocket in a heavily cross-chained situation. They don't say.
>
>I doubt that those researchers "found" that sprocket size matters. It
>is common knowledge and hardly needs a PhD student to find it. Perhaps
>I should go and do my PhD there.
>
> As for their finding that lubrication does not affect
>efficiency....the real issue is wear, not efficiency in my view. Clean
>polished steel operating in clean conditions like a lab will perform
>well without lubrication, especially at low speeds experienced by
>bicycle chains. On the road, even a tarred road, it is different. Grit
>will quickly get in there and spoil the party.
>
>As for lubrication being a seal. I don't think so. I have seen how
>easily grit and road dirt mixes with lubrication. I don't for a minute
>believe that lubrication "takes up space that would otherwise have
>been taken up by dirt". It transports dirt to the inside. Even wax
>transports dirt to the inside. That's easy to demonstrate.Oil is not
>as superflous as they seem to make out
>
>God forbid that bicycle manufacturers start advertising the energy
>efficiency of their drivechains. Already we have to put up with the
>nonsense of energy efficiency in pedals which have a low stack heigh
>with the cleat, and all "stiffer" bumph, imagine if we now have to put
>up with 98% fat-free type rubbish on marketing hype as well.
>
>Finally, if they (the researchers) think that chains have not evolved
>in the last 100 years, they haven't seen Carl Fogel's pictures.
>
>One thing I can't understand is their claim that tension decreases
>friction. Anyone have any views on this?
>
>
>Johan Bornman
Dear Johan,
Here's the real chain article from Spicer:
http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf
Here's another article on gear efficiency from Kyle and Berto:
http://www.ihpva.org/pubs/HP52.pdf
Cheers,
Carl Fogel
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Date: 25 Jun 2007 07:46:07
From:
Subject: Re: Bike Chain Efficiency Study
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On Jun 21, 12:39 pm, carlfo...@comcast.net wrote:
> On Thu, 21 Jun 2007 03:56:58 -0700, Johan Bornman
>
>
>
> <coldb...@telkomsa.net> wrote:
> >I came across this study on the efficiency of a bicycle drivetrain.
>
> >http://www.jhu.edu/news_info/news/home99/aug99/bike.html
>
> >In some ways I think academia is naive. Then again, this link points
> >not to the research paper but the Press Release and we all know that
> >PR is, well, PR.
>
> >The way I see this study is thus:
>
> >Approaching this experiment from the infra-red angle has been done
> >before in at least one study I've seen. This one correspondes with the
> >wide range of efficiency in the other study as well, ranging from
> >1%-19%.. One Percent loss is probably for a perfectly lined-up chain
> >going from biggest to biggest sprocket, a situation not possible on
> >real world bikes where cross-chaining will eliminate some of the
> >efficiency. 18 Percent energy loss is likely to be from Granny Gear to
> >11tooth sprocket in a heavily cross-chained situation. They don't say.
>
> >I doubt that those researchers "found" that sprocket size matters. It
> >is common knowledge and hardly needs a PhD student to find it. Perhaps
> >I should go and do my PhD there.
>
> > As for their finding that lubrication does not affect
> >efficiency....the real issue is wear, not efficiency in my view. Clean
> >polished steel operating in clean conditions like a lab will perform
> >well without lubrication, especially at low speeds experienced by
> >bicycle chains. On the road, even a tarred road, it is different. Grit
> >will quickly get in there and spoil the party.
>
> >As for lubrication being a seal. I don't think so. I have seen how
> >easily grit and road dirt mixes with lubrication. I don't for a minute
> >believe that lubrication "takes up space that would otherwise have
> >been taken up by dirt". It transports dirt to the inside. Even wax
> >transports dirt to the inside. That's easy to demonstrate.Oil is not
> >as superflous as they seem to make out
>
> >God forbid that bicycle manufacturers start advertising the energy
> >efficiency of their drivechains. Already we have to put up with the
> >nonsense of energy efficiency in pedals which have a low stack heigh
> >with the cleat, and all "stiffer" bumph, imagine if we now have to put
> >up with 98% fat-free type rubbish on marketing hype as well.
>
> >Finally, if they (the researchers) think that chains have not evolved
> >in the last 100 years, they haven't seen Carl Fogel's pictures.
>
> >One thing I can't understand is their claim that tension decreases
> >friction. Anyone have any views on this?
>
> >Johan Bornman
>
> Dear Johan,
>
> Here's the real chain article from Spicer:
>
> http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf
Having read this, I must offer my apologies to Johan. It was a naive
study, but not because of the marketing. There was no discussion of
the possible implications of driving the chainrings with a constant
angular velocity control rather than an oscillating power control. I
imagine that the amount of freehub slip and derailleur bounce that
occurs when you have an actual person powering the bike is
significant. As for sprocket size, they did reference previous
investigation into the matter, and showing that part of your study
agrees with previous findings is a common way of implying that the
rest of the study isn't a load of crap. They hardly claimed to have
discovered the effect.
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Date: 21 Jun 2007 15:28:39
From: mike.a.schwab@gmail.com
Subject: Re: Bike Chain Efficiency Study
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On Jun 21, 9:58 am, unforgive...@juno.com wrote:
> On Jun 21, 10:31 am, Johan Bornman <coldb...@telkomsa.net> wrote:
>
>
>
> > On Jun 21, 1:56 pm, unforgive...@juno.com wrote:
>
> > >> I'm not sure which part of this study you find naive. They also don't
> > > mention anything about PhD students. Industrial application projects
> > > are generally masters level.
>
> > > As for the chain tension, I imagine a loose chain bounces a bit each
> > > time it engages with a tooth. It is surprising that this effect
> > > outweighs added friction.- Hide quoted text -
>
> > > - Show quoted text -
>
> > Johan Bornman: I find the marketing of the study somewhat naive. The
> > press release writer seemed to miss the crucial points, all the things
> > I would have liked to know about the study. It really is irrelevant
> > whether this was a masters level or PhD level paper. Point is, I doubt
> > that the author "Found" that smaller sprockets have higher losses than
> > larger ones. I think that knowledge is in the public domain and
> > doesn't require a new study. But like I said, it's most likely the
> > marketing of the research that's at fault.
>
> > JB
>
> It was a press release written for a general audience.
> If you want the details, buy the journal:http://tinyurl.com/38r9xr
I played back that movie on the press release site. Did you see that
jockey wheel heat up? No wonder fixies get good efficiencies. Those
two sharp turns around the small jockey wheels and those high friction
jockey wheel bearings are where all the energy goes.
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Date: 22 Jun 2007 06:54:47
From: John Henderson
Subject: Re: Bike Chain Efficiency Study
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mike.a.schwab@gmail.com wrote:
> I played back that movie on the press release site. Did you
> see that jockey wheel heat up? No wonder fixies get good
> efficiencies.
> Those two sharp turns around the small jockey wheels and
> those high friction jockey wheel bearings are where all the
> energy goes.
I've always thought the lack of a rear derailleur/tensioner
could more than balance the efficiency loss in my Sram S7 hub
gears with "perfect" chainline - especially since jockey wheels
accumulate so much crud.
John
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Date: 21 Jun 2007 15:12:18
From:
Subject: Re: Bike Chain Efficiency Study
|
On Fri, 22 Jun 2007 06:54:47 +1000, John Henderson
<jhenRemoveThis@talk21.com > wrote:
>mike.a.schwab@gmail.com wrote:
>
>> I played back that movie on the press release site. Did you
>> see that jockey wheel heat up? No wonder fixies get good
>> efficiencies.
>> Those two sharp turns around the small jockey wheels and
>> those high friction jockey wheel bearings are where all the
>> energy goes.
>
>I've always thought the lack of a rear derailleur/tensioner
>could more than balance the efficiency loss in my Sram S7 hub
>gears with "perfect" chainline - especially since jockey wheels
>accumulate so much crud.
>
>John
Dear John,
Kyle and Berto compared a Shimano derailleur 27 (3x9) to several
brands of internal gearing:
http://www.ihpva.org/pubs/HP52.pdf
Figure 12 shows that the ordinary internal gear systems like Sturmey
Archer and Rohloff have lower transmission efficiency than the
derailleur on average.
(Averaging is necessary, since they're comparing 27 speeds to anywhere
from 4 to 14 speeds.)
The Browning 4 speed internal gear uses a different design and beat
the derailleur.
As for the heating of the pulleys, Spencer's actual article points
that the exciting infrared pictures don't correspond to the measured
efficiency:
"Infrared measurements of drive components indicate that frictional
losses in the chain cause the chain temperature to rise during
operation. This increase in temperature did not correlate
with measured efficiencies under various conditions of operation.
Infrared measurements on lubricated and delubricated chain links
showed that the frictional heating did not depend on lubrication."
http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf
Cheers,
Carl Fogel
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Date: 22 Jun 2007 08:09:58
From: John Henderson
Subject: Re: Bike Chain Efficiency Study
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carlfogel@comcast.net wrote:
> Kyle and Berto compared a Shimano derailleur 27 (3x9) to
> several brands of internal gearing:
>
> http://www.ihpva.org/pubs/HP52.pdf
>
> Figure 12 shows that the ordinary internal gear systems like
> Sturmey Archer and Rohloff have lower transmission efficiency
> than the derailleur on average.
I imagine that's all measured with a relatively clean
derailleur. What I'd be really interested in, is a comparison
between internal and external gear systems after a few thousand
miles of typical maintenance (unless I've missed something
that's already been published).
Given the rate at which jockey wheels "tighten up" with
accumulated oily grime, I wouldn't be suprised if the the
results are different.
John
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Date: 21 Jun 2007 07:58:40
From:
Subject: Re: Bike Chain Efficiency Study
|
On Jun 21, 10:31 am, Johan Bornman <coldb...@telkomsa.net > wrote:
> On Jun 21, 1:56 pm, unforgive...@juno.com wrote:
>
> >> I'm not sure which part of this study you find naive. They also don't
> > mention anything about PhD students. Industrial application projects
> > are generally masters level.
>
> > As for the chain tension, I imagine a loose chain bounces a bit each
> > time it engages with a tooth. It is surprising that this effect
> > outweighs added friction.- Hide quoted text -
>
> > - Show quoted text -
>
> Johan Bornman: I find the marketing of the study somewhat naive. The
> press release writer seemed to miss the crucial points, all the things
> I would have liked to know about the study. It really is irrelevant
> whether this was a masters level or PhD level paper. Point is, I doubt
> that the author "Found" that smaller sprockets have higher losses than
> larger ones. I think that knowledge is in the public domain and
> doesn't require a new study. But like I said, it's most likely the
> marketing of the research that's at fault.
>
> JB
It was a press release written for a general audience.
If you want the details, buy the journal:
http://tinyurl.com/38r9xr
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Date: 21 Jun 2007 07:31:40
From: Johan Bornman
Subject: Re: Bike Chain Efficiency Study
|
On Jun 21, 1:56 pm, unforgive...@juno.com wrote:
>> I'm not sure which part of this study you find naive. They also don't
> mention anything about PhD students. Industrial application projects
> are generally masters level.
>
> As for the chain tension, I imagine a loose chain bounces a bit each
> time it engages with a tooth. It is surprising that this effect
> outweighs added friction.- Hide quoted text -
>
> - Show quoted text -
Johan Bornman: I find the marketing of the study somewhat naive. The
press release writer seemed to miss the crucial points, all the things
I would have liked to know about the study. It really is irrelevant
whether this was a masters level or PhD level paper. Point is, I doubt
that the author "Found" that smaller sprockets have higher losses than
larger ones. I think that knowledge is in the public domain and
doesn't require a new study. But like I said, it's most likely the
marketing of the research that's at fault.
JB
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Date: 21 Jun 2007 04:56:23
From:
Subject: Re: Bike Chain Efficiency Study
|
On Jun 21, 6:56 am, Johan Bornman <coldb...@telkomsa.net > wrote:
> I came across this study on the efficiency of a bicycle drivetrain.
>
> http://www.jhu.edu/news_info/news/home99/aug99/bike.html
>
> In some ways I think academia is naive. Then again, this link points
> not to the research paper but the Press Release and we all know that
> PR is, well, PR.
>
> The way I see this study is thus:
>
> Approaching this experiment from the infra-red angle has been done
> before in at least one study I've seen. This one correspondes with the
> wide range of efficiency in the other study as well, ranging from
> 1%-19%.. One Percent loss is probably for a perfectly lined-up chain
> going from biggest to biggest sprocket, a situation not possible on
> real world bikes where cross-chaining will eliminate some of the
> efficiency. 18 Percent energy loss is likely to be from Granny Gear to
> 11tooth sprocket in a heavily cross-chained situation. They don't say.
>
> I doubt that those researchers "found" that sprocket size matters. It
> is common knowledge and hardly needs a PhD student to find it. Perhaps
> I should go and do my PhD there.
>
> As for their finding that lubrication does not affect
> efficiency....the real issue is wear, not efficiency in my view. Clean
> polished steel operating in clean conditions like a lab will perform
> well without lubrication, especially at low speeds experienced by
> bicycle chains. On the road, even a tarred road, it is different. Grit
> will quickly get in there and spoil the party.
>
> As for lubrication being a seal. I don't think so. I have seen how
> easily grit and road dirt mixes with lubrication. I don't for a minute
> believe that lubrication "takes up space that would otherwise have
> been taken up by dirt". It transports dirt to the inside. Even wax
> transports dirt to the inside. That's easy to demonstrate.Oil is not
> as superflous as they seem to make out
>
> God forbid that bicycle manufacturers start advertising the energy
> efficiency of their drivechains. Already we have to put up with the
> nonsense of energy efficiency in pedals which have a low stack heigh
> with the cleat, and all "stiffer" bumph, imagine if we now have to put
> up with 98% fat-free type rubbish on marketing hype as well.
>
> Finally, if they (the researchers) think that chains have not evolved
> in the last 100 years, they haven't seen Carl Fogel's pictures.
>
> One thing I can't understand is their claim that tension decreases
> friction. Anyone have any views on this?
>
> Johan Bornman
I'm not sure which part of this study you find naive. They also don't
mention anything about PhD students. Industrial application projects
are generally masters level.
As for the chain tension, I imagine a loose chain bounces a bit each
time it engages with a tooth. It is surprising that this effect
outweighs added friction.
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