Drive Train Effecieny

SSSHHHHHH!!!!! Don't let Shimano hear that! They'll go and change everything so we'll all have to
buy complete new drivetrain systems again the next time our chain needs replacing, or the small cog
wears out!!

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": geocities.comczcornerOpen ↗

(Steven) said:

And hearing all the noise in the Giro etc. about bike manafactures being able to make a bike
signifigantly less than the 16.5 pounds that the UCI set's as the lower limit of weight. My thought
is essentially this, why not make that bike but throw extra weight back in by making the drive
train more efficient.

Lets say that for arguments sake the average pro cylist puts out 400 watts during a climb up alp
d'huez and his drive train is 90% effecient.

Thing is, the data I've seen suggest a clean, well-adjusted drivetrain is closer to 98% efficient.
That doesn't leave a lot of room for improvement (at least not without spending a fortune on a chain
with itty bitty little bearings in every link).

That number hasn't changed in recent history, either - probably won't in the near future.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

Steven said:

And hearing all the noise in the Giro etc. about bike manafactures being able to make a bike
signifigantly less than the 16.5 pounds that the UCI set's as the lower limit of weight. My
thought is essentially this, why not make that bike but throw extra weight back in by making the
drive train more efficient.

The minimum weight of a bike set in UCI rules is 15 pounds, or 6.8 kg.

Quoted message said:

Lets say that for arguments sake the average pro cylist puts out 400 watts during a climb up alp
d'huez and his drive train is 90% effecient.

The problem with your argument is that the efficiency of a properly adjusted well-lubricated drive
train is much higher than 90 %. It's more like 98-99 %.

-as

(Steven) may have said:

I am sure making the drive train 1% more effecient isn't easy but on the other hand you don't here
much about "shimano's new 2004 drive train being .3% more effecient and I can't believe that we
have reached some major platue in effeciency, or that all drive trains perform exactly the same.

I will note that my own experience confirms one of the findings, on the *same bike*, with the same
*overall* cog ratio and the same pedal crank length, my average speed on my most usual ride is
22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to the freewheel
that has the 11 tooth top cog, and swap on the matching 38 big ring, the average speed drops to
17mph and the pedal effort goes up. The effective ratios are close to the same; 3.45 vs 3.42, not
enough to make that kind of a difference. There's a 13 tooth second cog on that 11-top freewheel,
though, and when I swap the 48 big ring back on and run in the 48/13 combination,, my speed goes to
21mph, and the perceived pedal effort is reduced relative to the 11/38 pair even though it's
actually a higher ratio.

I had wondered why the same resultant ratio would seem to be harder to pedal when literally
everything else was the same, but now I think I know where the problem is. I haven't decide what to
do about it yet; I may grab a 14-34 megarange freewheel and slap a 52 big ring on with it so that
I'll have an overdrive in the top combo and increased efficiency below that.

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Werehatrack said:

I will note that my own experience confirms one of the findings, on the *same bike*, with the same
*overall* cog ratio and the same pedal crank length, my average speed on my most usual ride is
22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to the
freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average speed
drops to 17mph and the pedal effort goes up. The effective ratios are close to the same; 3.45 vs
3.42, not enough to make that kind of a difference. There's a 13 tooth second cog on that 11-top
freewheel, though, and when I swap the 48 big ring back on and run in the 48/13 combination,, my
speed goes to 21mph, and the perceived pedal effort is reduced relative to the 11/38 pair even
though it's actually a higher ratio.

I had wondered why the same resultant ratio would seem to be harder to pedal when literally
everything else was the same, but now I think I know where the problem is. I haven't decide what
to do about it yet; I may grab a 14-34 megarange freewheel and slap a 52 big ring on with it so
that I'll have an overdrive in the top combo and increased efficiency below that.

Your comments interest me, because I had that impression when I was riding a derailleur bike (I am
now using a Rohloff Speedhub). The difference must be that the smaller chainrings and sprockets are
less efficient because there is more bending of the chain which induces more friction. The 14 speed
Rohloff Speedhub adds about a pound vs 27 speed Shimano Deore XT, and reduces the efficiency about
1-2%, especially in the lower gears where all three planetary clusters are involved. However, IMHO,
the 526% gear range, the even 13.7% stepping, and the ability to shift smoothly and quickly, even
when going uphill, makes up for the efficiency loss. When I first got the Speedhub, a few years ago,
we had a thread going on the then Compuserve cycling forum about efficiency. A chain drive is as
efficient as you can get, because there is the least friction and deformation under load. The
Speedhub adds an additional energy sink, but it is still amazingly efficient, which is not true of
other gear hubs.
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"When I see an adult on a bicycle, I do not despair for the future of the human race." HG Wells

"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I will note that my own experience confirms one of the findings, on the *same bike*, with the same
*overall* cog ratio and the same pedal crank length, my average speed on my most usual ride is
22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to the
freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average speed
drops to 17mph and the pedal effort goes up.

That makes no sense.

Peter Cole said:

"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I will note that my own experience confirms one of the findings, on the *same bike*, with the
same *overall* cog ratio and the same pedal crank length, my average speed on my most usual ride
is 22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to the
freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average speed
drops to 17mph and the pedal effort goes up.

That makes no sense.

I agree it does seem awfully extreme. I can see a fraction of a mph loss, but not a 20+% drop in
speed. At that point, I'd expect the chain to become too hot to handle.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

RE/

Quoted message said:

The Speedhub adds an additional energy sink, but it is still amazingly efficient, which is not true
of other gear hubs.

One thing that makes me sort of addicted to my Rohloffs is the "any gear, any time" aspect. It just
feels better...
-----------------------
PeteCresswell

Mark Hickey may have said:

Peter Cole said:

"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I will note that my own experience confirms one of the findings, on the *same bike*, with the
same *overall* cog ratio and the same pedal crank length, my average speed on my most usual ride
is 22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to the
freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average speed
drops to 17mph and the pedal effort goes up.

That makes no sense.

I agree it does seem awfully extreme. I can see a fraction of a mph loss, but not a 20+% drop in
speed. At that point, I'd expect the chain to become too hot to handle.

I haven't checked to see if there's any friction heating, but I don't think it would necessarily be
present; there's a lot of surface area, substantial airflow over the presumably heated mass, and a
fairly low amount of energy involved in point of fact. It's possible that there's just something odd
about that 11, but I haven't got another one to test it against. At first, I thought it might be a
worn cog making the effort higher, but the 11 actually appears to have *less* wear than the 14, and
I didn't see any change with a brand new chain either. (One good thing came of this, at least; I now
have a spare chain on hand for the next time I need one.)

BTW, FWIW, an engineer acquaintance confirms that the "big cogs make more efficient chain drives"
effect is a known datum, but that it has practical limits; there's very definitely a point of
diminishing returns on making the cog bigger. He said it would take a lot of digging to find the
answer as to what's likely to be optimal.

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Werehatrack said:

Mark Hickey may have said:

Peter Cole said:

"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...
> I will note that my own experience confirms one of the findings, on the *same bike*, with the
> same *overall* cog ratio and the same pedal crank length, my average speed on my most usual
> ride is 22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to
> the freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average
> speed drops to 17mph and the pedal effort goes up.

That makes no sense.

I agree it does seem awfully extreme. I can see a fraction of a mph loss, but not a 20+% drop in
speed. At that point, I'd expect the chain to become too hot to handle.

I haven't checked to see if there's any friction heating, but I don't think it would necessarily
be present; there's a lot of surface area, substantial airflow over the presumably heated mass,
and a fairly low amount of energy involved in point of fact. It's possible that there's just
something odd about that 11, but I haven't got another one to test it against. At first, I thought
it might be a worn cog making the effort higher, but the 11 actually appears to have *less* wear
than the 14, and I didn't see any change with a brand new chain either. (One good thing came of
this, at least; I now have a spare chain on hand for the next time I need one.)

What makes you think that your power output was constant?

Maybe the chain is wearing against the face of the rear dropout when you're in the small cog. I've
had that happen---I no longer remember the cause. It should be rather obvious...

Joe Riel

(Pete Cresswell) said:

RE/

Quoted message said:

The Speedhub adds an additional energy sink, but it is still amazingly efficient, which is not
true of other gear hubs.

One thing that makes me sort of addicted to my Rohloffs is the "any gear, any time" aspect. It
just feels better...
-----------------------
PeteCresswell

Amen! The rider who is going for extreme speed or extreme endurance or both will want to chop the
weight and increase the efficiency. For everyone else the Speedhub makes a lot of sense, except
for the price. I have one on each of my custom hybrid bikes (read that as touring bikes with
straight handlebars). The newer one, a Waterford Adventure Cycle frame with S and S couplings, I
have in a heavier touring configuration 700 x 38 tires, full tool kit, back rack etc. I don't plan
to go fast with this bike because I want to enjoy the scenery and stop along the way. The older
one, a Klein Adept I have striped down to minimize weight, and have 700 x 28 tires. With it, at
age 66, I can do a hilly century in 7-7 1/2 hours riding with about an hour of rest stops. That's
good enough for me.
--
Cheers! OliverS When replying personally, remove "_removespam_"

"When I see an adult on a bicycle, I do not despair for the future of the human race." HG Wells

Joe Riel may have said:

What makes you think that your power output was constant?

In point of fact, I think it *wasn't*, but part of the reason it wasn't constant is that the effort
was high enough that I never reached the cadence that works best for me. It's odd, but there's a
sort of "effort hump" that I hit, just past which I settle into a rhythm and output that I can keep
up for a couple of hours with no trouble. If I don't get to it, I tire much more quickly. This may
be one of the effects of age; I never had that happen when I was younger.

BTW, I've observed that the hump can be passed in a lower gear, and I can keep on going easily, but
just at a lower speed.

Quoted message said:

Maybe the chain is wearing against the face of the rear dropout when you're in the small cog. I've
had that happen---I no longer remember the cause. It should be rather obvious...

No, it was running free with no restrictions, but a small difference in effort is detectable even
with the bike just flipped and spun unloaded. In fact, I first noticed it that way, and I thought I
had to be nuts; no way that it could be harder to spin up when the ratio was the same. Then I got on
it and went for a run, and I couldn't hit my normal speed, so I thought *this is *really* nuts, WTF
is going on?". So far, I can't find anything that's a reasonable explanation except the fact that
the 11 cog seems to be making the effort higher. So, for the moment, that freewheel is going to
gather dust. Sooner or later, I'll find another 11 cheap, and I'll try it. I won't be too surprised
by the results no matter what they are. It could very well be that *this* 11 is an underperformer
relative to some others, and that when combined with the small-cog effect, produces an exaggerated
result. Why that should be, I may find out eventually.

Meanwhile, a workable solution is at hand, and I'll simply use it. It is not mandatory that I know
*why* it works at this point.

BTW, my engineer contact confirms that the sparse data he's got indicates a smaller-cog penalty that
shouldn't be anywhere near this severe if the two cogs are otherwise the same in design
characteristics, so the small-cog-effort theory remains unproven as the *sole* cause in this
instance. He noted that it should be more speed-dependent, and that bike chain speeds are low enough
that it wasn't likely to be a big issue, maybe not even measurable; any time you change the
direction of a chain, apparently, you get some (small) loss; the sharper the directional change, the
greater the loss, with some limits. The Johns Hopkins folks saw a diff that was on the order of 10%
over their *entire* range of tests, so some of that doubtless had other factors bearing on it.
Still, they found that cog size did matter, so maybe there's a hidden bugger factor somewhere.

I'm still amused (and unsurprised) that the lube was no factor at all.

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Werehatrack said:

Joe Riel may have said:

What makes you think that your power output was constant?

In point of fact, I think it *wasn't*, but part of the reason it wasn't constant is that the
effort was high enough that I never reached the cadence that works best for me. It's odd, but
there's a sort of "effort hump" that I hit, just past which I settle into a rhythm and output that
I can keep up for a couple of hours with no trouble. If I don't get to it, I tire much more
quickly. This may be one of the effects of age; I never had that happen when I was younger.

BTW, I've observed that the hump can be passed in a lower gear, and I can keep on going easily,
but just at a lower speed.

A couple of hours in the 11 tooth cog on the back? How do you manage that!?!

Dani

asqui' may have said:

Werehatrack said:

Joe Riel may have said:

What makes you think that your power output was constant?

In point of fact, I think it *wasn't*, but part of the reason it wasn't constant is that the
effort was high enough that I never reached the cadence that works best for me. It's odd, but
there's a sort of "effort hump" that I hit, just past which I settle into a rhythm and output
that I can keep up for a couple of hours with no trouble. If I don't get to it, I tire much more
quickly. This may be one of the effects of age; I never had that happen when I was younger.

BTW, I've observed that the hump can be passed in a lower gear, and I can keep on going easily,
but just at a lower speed.

A couple of hours in the 11 tooth cog on the back? How do you manage that!?!

So far, I haven't, with the 11 that I've got. My current top cogs that get used regularly are a 14
(with a 48 front) on the main mtb, and 52/13 on the road bike. I had hoped to swap the 11 on to the
mtb and get a more challenging top cog, but the effort was way too high, so I swapped front rings to
run it with almost the same resulting top/top ratio, and didn't get the expected result. (I ride the
mtb more than the road bike because I have to hop a lot of curbs, and the fatter tires seem to
handle this better.) That's when I went "Huh? WTF?" So, I swapped back and kept on going, then I saw
the post at the top of the thread, read the article, and did an "Aha!" that may have been a trifle
premature. There pretty much has to be more than just small cog inefficiency involved, but so far, I
can't see what else to cite. It just doesn't make a lot of sense, any way I look at
it. In time, it all will become clear, though; of that, I am confident.

As for how I can run in top combo most of the time, it's probably not as steep a ratio as yours
overall, and we have terrain that's almost as flat as South Florida. Downshifting is mostly just for
traffic lights and the few spots where the bike path dives under a bridge crossing the bayou. Even
when I'm off the path and running on regular city streets, I'm likely to be running in a pair that's
about 3.4:1 over half the time unless there's a headwind, and I seldom cruise at lower than 2.75:1
even when it's hot, windy, and I'm already tired. (If I have to drop more than that far to keep the
rhythm on the flat and level, it's time for a rest break and some water.) If I'm going to be riding
where there are some longer grades, though, I'm definitely going to want a taller top combo to use.

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"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Mark Hickey may have said:

Peter Cole said:

"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...
> I will note that my own experience confirms one of the findings, on the *same bike*, with the
> same *overall* cog ratio and the same pedal crank length, my average speed on my most usual
> ride is 22mph when I'm running with the 48 front ring and 14 rear top cog, but when I swap to
> the freewheel that has the 11 tooth top cog, and swap on the matching 38 big ring, the average
> speed drops to 17mph and the pedal effort goes up.

That makes no sense.

I agree it does seem awfully extreme. I can see a fraction of a mph loss, but not a 20+% drop in
speed. At that point, I'd expect the chain to become too hot to handle.

I haven't checked to see if there's any friction heating, but I don't think it would necessarily
be present; there's a lot of surface area, substantial airflow over the presumably heated mass,
and a fairly low amount of energy involved in point of fact. It's possible that there's just
something odd about that 11, but I haven't got another one to test it against. At first, I thought
it might be a worn cog making the effort higher, but the 11 actually appears to have *less* wear
than the 14, and I didn't see any change with a brand new chain either. (One good thing came of
this, at least; I now have a spare chain on hand for the next time I need one.)

That speed differential, using nominal values for other parameters, shows about 100W
(additional)power loss. It's absurd to thing an 11 tooth sprocket would do that.

Quoted message said:

BTW, FWIW, an engineer acquaintance confirms that the "big cogs make more efficient chain drives"
effect is a known datum, but that it has practical limits; there's very definitely a point of
diminishing returns on making the cog bigger. He said it would take a lot of digging to find the
answer as to what's likely to be optimal.

But it takes only common sense to realize that your numbers are way, way off. Larger sprockets are
more efficient, since the chain goes through a smaller bend angle as it dis/engages, but the effect
]is *much* smaller than what you claim to observe.

Peter Cole' may have said:

But it takes only common sense to realize that your numbers are way, way off. Larger sprockets are
more efficient, since the chain goes through a smaller bend angle as it dis/engages, but the effect
]is *much* smaller than what you claim to observe.

Other factors have since been deduced, but the cog's portion of the effect is present; it's just not
the only thing happening. There is definitely a higher effort required for the same overall ratio,
though, and it's also higher than the theory would predict. There's still no conclusive answer as to
why, and I'm going to have to sideline this one for lack of time to mess with it for now; my
business just got a bunch of orders for merchandise, and it's time to finalize last year's taxes, so
I'm not going to be getting fingers greasy for several weeks at least.

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Werehatrack said:

On Sun, 3 Aug 2003 05:32:13 +0000 (UTC), "asqui" <[email hidden]> may have said:

[...]

Quoted message said:

crossing the bayou. Even when I'm off the path and running on regular city streets, I'm likely to
be running in a pair that's about 3.4:1 over half the time unless there's a headwind, and I seldom
cruise at lower than 2.75:1 even when it's hot, windy, and I'm already tired. (If I have to drop
more than that far to keep the rhythm on the flat and level, it's time for a rest break and some
water.) If I'm going to be riding where there are some longer grades, though, I'm definitely going
to want a taller top combo to use.

Just out of interest, what sort of cadence do you cruise at?

Dani

asqui' may have said:

Werehatrack said:

On Sun, 3 Aug 2003 05:32:13 +0000 (UTC), "asqui" <[email hidden]> may have said:

[...]

Quoted message said:

crossing the bayou. Even when I'm off the path and running on regular city streets, I'm likely to
be running in a pair that's about 3.4:1 over half the time unless there's a headwind, and I
seldom cruise at lower than 2.75:1 even when it's hot, windy, and I'm already tired. (If I have
to drop more than that far to keep the rhythm on the flat and level, it's time for a rest break
and some water.) If I'm going to be riding where there are some longer grades, though, I'm
definitely going to want a taller top combo to use.

Just out of interest, what sort of cadence do you cruise at?

Beats the bleep out of me. I know when I hit it, but I haven't tried to measure it. There are levels
of data collection to which I have not yet needed to go. "How far" and "how fast" is all I really
measure for now.

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"Werehatrack" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Peter Cole' may have said:

But it takes only common sense to realize that your numbers are way, way

off.

Quoted message said:

Quoted message said:

Larger sprockets are more efficient, since the chain goes through a smaller bend angle as it
dis/engages, but the effect ]is *much* smaller than what

you

Quoted message said:

Quoted message said:

claim to observe.

Other factors have since been deduced, but the cog's portion of the effect is present; it's just
not the only thing happening. There is definitely a higher effort required for the same overall
ratio, though, and it's also higher than the theory would predict.

"Theory" would probably predict something less than 0.1%. You're claiming around 100%. You're off by
3 orders of magnitude.

Quoted message said:

There's still no conclusive answer as to why,

I think your bike is broken, why don't you have a mechanic look at it?