What about drive train friction? Has anybody attempted to measure it?

[Louis]

For all the talk (not necessarily on this site) about how much effort and money is expended to shave 50 grams in bike weight, what about loses in the drive train due to friction?

I’ve seen some hubs being advertised as better because they use ceramic bearings and presumably have lower friction, but nothing about the drive train proper, which I’m guessing is much worse than the wheels.

You can get a feel for the static friction by seeing how much force you have to apply to your pedal to get it too move (easiest if the cranks are horizontal) and that can be a surprisingly large force. (I was playing around with this last night as I lubed my chain.) However, I’ve never heard of anybody actually trying to measure this with the intent of improving the bike. I believe that I read somewhere that typical power losses due to this are on the order of several percentage points, which over an entire race would not be negligible, especially on a flattish course.

Clarification, I’m not a racer, and in my case the engine needs a lot more improvement than the transmission, so it’s not an issue for me. I’m just wondering why folks obsess over tiny weight savings but not over the drive train.

Louis

[saab2000]

Put your bike in your lowest gear. 39x23 or whatever it is. Spin the crank backwards. Does it spin several revolutions? Or stop? It should spin freely.

This is a good question and i think old freewheels used to have less internal friction than cassettes. Still, it is a very small part of the whole thing and losing a few pounds would make up for the 1/10 of a watt lost in the drivetrain.

[Jason E]

Put your bike in your lowest gear. 39x23 or whatever it is. Spin the crank backwards. Does it spin several revolutions? Or stop? It should spin freely.

This is a good question and i think old freewheels used to have less internal friction than cassettes. Still, it is a very small part of the whole thing and losing a few pounds would make up for the 1/10 of a watt lost in the drivetrain.

Argee and disagree, politely.

The first part, about determining friction..... If the most important place (for the sake of your example) to save some watts were when pointing up a hill, you are not coasting, lost watts would be in Hub Bearings, Chain, Frame-Flex, and derailleur adjustments, but not in the resistance while coasting, no?

Losing a few pounds and spending several more hours a week in the sadlle would make all of us better, even with crappy wheels.

[David Kirk]

Drive train losses are very small. I've seen studies pegging them at 2% or less....IF the drive train is clean and not worn. Throw in some dirt, a lack of chain lube and a stretched chain on worn cogs and the losses go way up.

So keep it clean and fresh.

Dave

[sfscott]

But the bike always seems easier to pedal and faster when I do a quick clean and lube pre-ride with some Pro-Link.

I definitely feel a difference, so if it's all in my head, I guess that is ok.

[xcandrew]

Here is some discussion that I pulled from rec.bicycles.tech a few years ago (I'm too lazy to find the reference... use googlegroups to find the whole discussion and who posted what):

Measurements of Efficiency of Chain and Shaft Drives
>
> Section 1.2.2
>
> Contributed by Chris Juden, CTC Technical Officer, cycling@ctc.org.uk
>
> 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.

Formatting might not be clear, but the first column is single speed, the next three columns are 3 spd hub gears (low, 1:1, high), and the last three columns are rear sprockets in a derailleur system. The most obvious trend with all setups is that efficiency improves at higher power levels.

Interesting "Human Power" journal article: http://www.ihpva.org/pubs/HP52.pdf

I have issues 50 and 51 on my computer which also have interesting efficiency testing, answering questions about things like how efficient or inefficient 11 and 12 tooth sprockets are. (Smaller sprockets are less efficient, but they increase chain tension which increases efficiency, which more than offsets the loss by the small size... at least for the combinations tested.)

[Frustration]

Strictly speaking drive train, that's not free hub or wheels, but cranks and der pulleys, There are hardly any watts needed to turn cranks or pulleys.


Over time if your bb breaks down, then there's some measurable power lost under heavy load, but with things in good working order and a well maintained chain, There's very little in it.

Part of the advantage of Ceramics maintained well (sealed and retained in the right materials) is that they degrade slower too...

[Kevan]

lost to it.

[ada@prorider.or]

, what about loses in the drive train due to friction?

for drive train friction on bearings there is a research done
at philips

apart from this its also done for a chain

this becuase we have tried to make a chain with ceramics
and try to do this with any lubrication in future
the test showed very little friction
with in a watt

the gain was very litle with ceramics on a chain

what made a great differance was the wear

at the end there was the conclusion to stay on the high end steel chains as the cost where to high for ceramics
altough it would end rusty chains

[obtuse]

for drive train friction on bearings there is a research done
at philips

apart from this its also done for a chain

this becuase we have tried to make a chain with ceramics
and try to do this with any lubrication in future
the test showed very little friction
with in a watt

the gain was very litle with ceramics on a chain

what made a great differance was the wear

at the end there was the conclusion to stay on the high end steel chains as the cost where to high for ceramics
altough it would end rusty chains

cees-
what about using special lubricants to reduce friction and wear? what did the studies at philips come up with as a conclusion there? and where are the best places to reduce friction on a racing bicycle?

obtuse

[asgelle]

For all the talk (not necessarily on this site) about how much effort and money is expended to shave 50 grams in bike weight, what about loses in the drive train due to friction?

Several people have measured drivetrain losses by combining an SRM and Power-Tap on the same bike. The discussion is over at the wattage list on lists.topica.com. As I remember, the losses were in the range of 1-2% of the total power with a slight dependence on speed.

[ada@prorider.or]

cees-
what about using special lubricants to reduce friction and wear? what did the studies at philips come up with as a conclusion there? and where are the best places to reduce friction on a racing bicycle?

obtuse
well not too much grease in bearings

(remember grease is oil on soap basis)
the best is oil of course this depands on the force and surface presure and the lube
there is not such thing as special lube ,there are lube for special apllications and force distribution
soap is used to keep the oil on its place
the sort od soap can be differant and its friction
ceramics lube for instance best is inside water ,but this is impossible for a chain on a bike ,so they use a lube like teflon and its molecule with differant size´s
to prevent wear is choose the best surfarce contact so basicly devide the force over so big possible surface ,so what to do to lube a chain is use a tiny teflon molecule and use a special liguid to transport his on the place where it has to be , there are several let call it thickness of this transport agent
the teflon can have a tremendous load and stick to the surface and also filles a little a cap between two surface (here come choosing the right molecule size)
experiance shows that a chain with a certain teflon molecul size on a road bike can do the job
but for mountain bike it will do not because of the rubble thats in the envoirment


the best place to reduce friction is on the tyre´s and the air

in drive train
bearing sealings
and good lube chain
also hard enough cog set here i mean e module
and good adjusted bearings and lubricated (not too much)

[saab2000]

Cees,

Are ceramic bearings a good deal? I know they are really, really expensive. But will they be more durable? And lower friction? Some of the claims made, especially by FSA, are stunning and I have a hard time believing it can make that much difference.

What is the future of ceramic bearings?

[ada@prorider.or]

Cees,

Are ceramic bearings a good deal? I know they are really, really expensive. But will they be more durable? And lower friction? Some of the claims made, especially by FSA, are stunning and I have a hard time believing it can make that much difference.

What is the future of ceramic bearings?
http://forums.thepaceline.net/showthread.php?t=20051

above link what i said before about ceramic bearings


they will be more durable lower friction but hard to
maintain in evrydays bike
and the figure was for full ceramics (wich cost a fortune)
and saves so little
if i needed it for win a race and had money enough i would do it ,if i had money enough and would show off to others i would do it

as a poor racer i spent my money on tyre´s wich gain much and much more

(but he i am a dutch man like a other dutch man invent the copper tread by fighting for a cent)

[saab2000]

I already use good tires!! I need all the help I can get!! :D Thanks for the answer. Interesting.

[obtuse]

http://forums.thepaceline.net/showthread.php?t=20051

above link what i said before about ceramic bearings


they will be more durable lower friction but hard to
maintain in evrydays bike
and the figure was for full ceramics (wich cost a fortune)
and saves so little
if i needed it for win a race and had money enough i would do it ,if i had money enough and would show off to others i would do it

as a poor racer i spent my money on tyre´s wich gain much and much more

(but he i am a dutch man like a other dutch man invent the copper tread by fighting for a cent)


there is nothing wrong with bringing your own potatos with you on vaction!

obtuse

[ada@prorider.or]

there is nothing wrong with bringing your own potatos with you on vaction!

obtuse

mmm
german number plate!

[ada@prorider.or]

I already use good tires!!.
with good tyre´s
i mean low roll coeff .

.0031 as example

[Insight Driver]

Think in terms of common sense. If drivetrain losses are in the 1-2% range, then any work in reducing it by some small amount in the end means almost nothing. As a human body is the greatest source of drag on a bike, it has been shown that a much higher percentage improvement can be had by just getting into a more aerodynamic position. This what a time trial bike and rider set up is all about. As far as climbing at a slower pace than professionals, then absolute weight makes the biggest difference and where is the largest percentage of weight? In the rider, of course.

All the time studies indicate that a person can make changes that improve their riding power, endurance and skill, yet these persons still say, yeah, yeah, to it, and keep looking for something in the bike that could improve things. :butt:

[obtuse]

mmm
german number plate!


maybe the registration tax is lower in germany. :rolleyes:

obtuse

[saab2000]

maybe the registration tax is lower in germany. :rolleyes:

obtuse

Maybe. Maybe not.

It sho is high in Switzerland. Thankfully the sugarmama paid that!!! :beer:

[palincss]

Argee and disagree, politely.

lost watts would be in Hub Bearings, Chain, Frame-Flex, and derailleur adjustments, but not in the resistance while coasting, no?



Research seems to show that energy is not lost in frame flex, but rather is returned to the drivetrain.

[stevep]

i think that there is more energy loss in the derailleur pulleys that anywhere else in the system.
cees, true?

if you spin the crank backward as described above by saab but you just take tension off the pulleys by pushing the cage forward a little bit the crank spins far more freely. this back tension works against the drive all the time...

[goonster]

if you spin the crank backward as described above by saab but you just take tension off the pulleys by pushing the cage forward a little bit the crank spins far more freely. this back tension works against the drive all the time...

Exactly, and that tension varies with derailer position (i.e. it is greater when bigger cogs are selected).

A VBQ article pointed out that there was an era when racers obsessed over reducing mechanical friction, more so than weight or aerodynamics, and favored derailers with constant or adjustable spring tension. They also fretted much more over Q-factor and chainline (their chains permitted less side-to-side flex) than we do today, which is to say barely at all.

All sensible people agree that the bike is not the first place to look for performance gains, but it is not unreasonable for curious minds to think this stuff through.