Funny Chain Lubricant Story

wrote in message
...

So, Carl, do you lube a chain or leave it dry?

On Sun, 15 Jun 2008 20:39:09 -0700, "Tom Kunich" cyclintom@yahoo.
com wrote:


wrote in message
.. .

So, Carl, do you lube a chain or leave it dry?

Dear Tom,

As I said earlier in this thread, I'm now spraying my chain with
Dupont Teflon wax.

But I doubt that it's much better overall (or worse) than all the
other schemes . . .

Such as the exotic oils at incredible prices used by many happy RBT
posters and local bike shops, melted wax blended with just a hint of
an unassuming table oil (Frank's preference, with years of good
results), the liquid drip-on waxes at perfume-bottle prices that some
people swear by, or the drippings from discarded motor-oil cans
extracted from dumpsters (Jobst has mentioned doing this to stop
squeaks after rain in the Alps).

It's about $6 a can at Lowes hardware.

Like just about everyone, I end up replacing exposed chains.

My impression is that people who ride where it's wet and muddy buy
chains more often--gosh, what a surprise!

But every bike's tires stir up that invisible cloud of fine road dust,
which gets into the chain guts no matter what magic lube is used.
Small as the dust particles are, they're harder than the chain.

And the road dust particles have to be small--they can't do their
dirty work unless they fit between a new pin and roller, a space
smaller than most micrometers can measure.

Bicycle chains that run in cases last longer, partly because they're
protected a little from road dust, but mostly because most such bikes
aren't ridden very hard--the more gently you pedal, the longer the
chain lasts.

If the oil is black, it's full of road dust. Every bike chain in a
case that I've seen (not that many) was black as sin.

Some motorcycles ran primary chains in sealed oil baths (truly sealed,
not just a bike chain case). They essentially lasted forever, partly
because there was virtually no polishing action with the clean oil and
partly because they were double-row chains, which spread the load out.

It's worth noting that no one has produced a credible test showing a
chain in action transmitting significantly different power when
different lubes are used--most of the power loss is due to chordal
action, the variation in chain speed caused by straight links of chain
suddenly wrapping around the "circle" of a sprocket. That vibration is
why even the motorcycle chains running in sealed oil baths lose around
3% power.

The wear, annoying though it is, is a separate matter and doesn't cost
much power. It takes forever to polish about 0.0025" of metal off all
those rollers, and that wear depends on the road dust between the
surfaces.

Cheers,

Carl Fogel

Carl Fogel wrote:

The discussion hasn't mentioned protection from corrosion, but it
should have. Wear of corroded surfaces, with their dramatically
greater surface area, is much greater.

I'm not sure what sort of corrosion you have in mind, but my chain
sees nothing but oil and on occasion rain water, that in time
washes all oil out of the chain. Water works as a good lubricant
but unfortunately evaporates readily and leaves the chain
unlubricated.

http://www.sheldonbrown.com/brandt/chain-care.html

Calculations of chain efficiency are interesting, and no doubt
well done. But, they are beside the point if little energy is
needed to remove material, with abrasives, from the wearing parts
of the chain.

I think you are looking in the wrong place. The smaller the
sprocket, the larger the articulation angle and proportionately
the wear and minuscule energy loss in the hinge-pin. For
instance, two 60t sprockets make the chain bend 24° in one
revolution of the chain. a 53t-11t combination make the chain bend
79°.

And consider the noise. If the wear on the chain were as bad as
the noise of a squeeking drive train is offensive, you'd
certainly lube your chain.

If it squeaks it must be clean. Grit does not allow
metal-to-metal stick-slip squeak.

Great feature of this group is that Carl might find the numbers
to measure just how efficiently a dry, unlubricated chain, can
drive the next rider nuts. smile Hint: Requires truly minimal
energy.

Do your own analysis if you have a grasp of the subject that you
feel allows you to write these lines.

Admittedly, there's little to no tension in the rear derailleur
idlers, but wouldn't that be where the greatest chain bend angle
would be found?

Yes, there's no load on the chain on the bottom run, except for its
own weight and the feeble derailleur spring.

Jobst mistakenly included the lower run in his explanation, using 4
turns, instead of just the upper run's 2 turns, where the chain is
under load.

The example I cited only compares what the ratio of bends in chains is
for the combinations chosen. It does not say where the load is or
what wear there is. Derailleur idlers cause bends that when clean and
unlubricated, cause the squeak s that people mention. It is not the
loaded entry or exit from sprockets.

Jobst Brandt

On Jun 15, 11:13 pm, wrote:

Dear Ralph,

Yes, there's no load on the chain on the bottom run, except for its
own weight and the feeble derailleur spring.

Jobst mistakenly included the lower run in his explanation, using 4
turns, instead of just the upper run's 2 turns, where the chain is
under load.

The upper run is where the wear occurs because the pins turn under
load as the chain exits the rear and engages the front.

Power loss is different than wear.

The power lost polishing the pins under load is quite small. It takes
thousands of miles to polish each pin interface about 0.0025" and
elongate a foot of chain a whole 1/16th of an inch.

Most of the loss occurs because of what's called chordal action, which
is why lubrication makes little difference to power transmission.

When the chain engages the sprocket, the speed changes. In crude
terms, the link snaps down as it pulls onto the front sprocket and
takes a shortcut across the "circle" of the sprocket, a tiny chord
across the inside of the circle.

So the long, heavy chain run is constantly speeding up and slowing
down a little bit, which means that it vibrates. Accelerating that
mass in a twanging motion takes power.

The smaller the sprocket, the greater the shortcut. The bigger the
shortcut the link takes across the inside of the sprocket "circle",
the greater the change in chain speed, vibration, and power loss.

Here's a page that gives the equation for such chordal action:
http://chain-guide.com/basics/2-2-1-chordal-action.html

As the graph at the bottom shows, the chain speed variation due to
chordal action is almost nothing at 53 teeth (0.1756%), but is about
twenty times as much at 11 teeth (4.0507%).

Keep in mind that the % of chain speed variation is not a direct
measure of power loss--that's a different percentage. But the two are
fairly well related, which is one reason why small sprockets lose more
power than large sprockets.

The speed-change rises very steeply as the tooth count approaches 11
teeth:

teeth
chordal-speed-variation
increase-from-16-teeth

16 1.9215%
15 2.1852% +13.7%
14 2.5072% +30.5%
13 2.9058% +51.2%
12 3.4074% +77.3%
11 4.0507% +110.8%

That's why land-speed-record bikes with two chains connected by a
jackshaft use much bigger sprockets than necessary to obtain their
high gearing.

A pair of ordinary 52x12's coupled by a jackshaft would produce
18.7-to-1 gearing, roughly what's used.

But the two chains would be vibrating badly because of the 12-tooth
sprockets, whose average chain-speed variation is 3.4%.

So Rompelberg used a 70x15 and 60x16 (only 17.5-to-1 gearing) at first
and then 70x15 and 60x14 (20-to-1 gearing) for his land-speed records.
That reduced the average chain-speed-variation down to around 2% and
2.3%, with the mismatched tooth-counts avoiding the two chains
vibrating in synchronization.


It's certainly true that low tooth counts give more chordal action and
less smooth power transmission. But I'm not convinced that this, in
itself, causes a loss in efficiency (or power, or energy).

If you look at the chain drive as a thermodynamic system, any energy
wasted has to leave as heat. Friction generates heat and (usually)
wastes energy. Do you have evidence that chordal action does the
same, beyond what comes from the friction of the usual flexing the
links at the bends?

You said "So the long, heavy chain run is constantly speeding up and
slowing down a little bit, which means that it vibrates. Accelerating
that mass in a twanging motion takes power." I'm not convinced that
it does - or rather, I think that if it does, it must be buried in
some secondary or tertiary effect. IOW, I think the energy invested
in the vibration is negligible, and/or almost all recovered.

As an analogy, riding a bike on a smooth road with a series of gentle
hills or undulations (say, on a 100 foot wavelength) has the
bike&rider accelerating slightly down hills, then decelerating on the
way back up. But if it weren't for the secondary effect of increased
aero losses on the higher speed portions, there wouldn't be any
significant energy loss caused by the accelerations. And in fact,
those sorts of roads tend to give higher TT speeds, IIRC.

So: more roughness in the drive motion, I agree. Larger bend angle,
therefore a tad more friction loss, I agree. But aside from that, do
you have an explanation of where chordal action causes the energy
actually to leave the system?

- Frank Krygowski

On Mon, 16 Jun 2008 07:56:27 -0700 (PDT), Frank Krygowski
wrote:

On Jun 15, 11:13 pm, wrote:

Dear Ralph,

Yes, there's no load on the chain on the bottom run, except for its
own weight and the feeble derailleur spring.

Jobst mistakenly included the lower run in his explanation, using 4
turns, instead of just the upper run's 2 turns, where the chain is
under load.

The upper run is where the wear occurs because the pins turn under
load as the chain exits the rear and engages the front.

Power loss is different than wear.

The power lost polishing the pins under load is quite small. It takes
thousands of miles to polish each pin interface about 0.0025" and
elongate a foot of chain a whole 1/16th of an inch.

Most of the loss occurs because of what's called chordal action, which
is why lubrication makes little difference to power transmission.

When the chain engages the sprocket, the speed changes. In crude
terms, the link snaps down as it pulls onto the front sprocket and
takes a shortcut across the "circle" of the sprocket, a tiny chord
across the inside of the circle.

So the long, heavy chain run is constantly speeding up and slowing
down a little bit, which means that it vibrates. Accelerating that
mass in a twanging motion takes power.

The smaller the sprocket, the greater the shortcut. The bigger the
shortcut the link takes across the inside of the sprocket "circle",
the greater the change in chain speed, vibration, and power loss.

Here's a page that gives the equation for such chordal action:
http://chain-guide.com/basics/2-2-1-chordal-action.html

As the graph at the bottom shows, the chain speed variation due to
chordal action is almost nothing at 53 teeth (0.1756%), but is about
twenty times as much at 11 teeth (4.0507%).

Keep in mind that the % of chain speed variation is not a direct
measure of power loss--that's a different percentage. But the two are
fairly well related, which is one reason why small sprockets lose more
power than large sprockets.

The speed-change rises very steeply as the tooth count approaches 11
teeth:

teeth
chordal-speed-variation
increase-from-16-teeth

16 1.9215%
15 2.1852% +13.7%
14 2.5072% +30.5%
13 2.9058% +51.2%
12 3.4074% +77.3%
11 4.0507% +110.8%

That's why land-speed-record bikes with two chains connected by a
jackshaft use much bigger sprockets than necessary to obtain their
high gearing.

A pair of ordinary 52x12's coupled by a jackshaft would produce
18.7-to-1 gearing, roughly what's used.

But the two chains would be vibrating badly because of the 12-tooth
sprockets, whose average chain-speed variation is 3.4%.

So Rompelberg used a 70x15 and 60x16 (only 17.5-to-1 gearing) at first
and then 70x15 and 60x14 (20-to-1 gearing) for his land-speed records.
That reduced the average chain-speed-variation down to around 2% and
2.3%, with the mismatched tooth-counts avoiding the two chains
vibrating in synchronization.


It's certainly true that low tooth counts give more chordal action and
less smooth power transmission. But I'm not convinced that this, in
itself, causes a loss in efficiency (or power, or energy).

If you look at the chain drive as a thermodynamic system, any energy
wasted has to leave as heat. Friction generates heat and (usually)
wastes energy. Do you have evidence that chordal action does the
same, beyond what comes from the friction of the usual flexing the
links at the bends?

You said "So the long, heavy chain run is constantly speeding up and
slowing down a little bit, which means that it vibrates. Accelerating
that mass in a twanging motion takes power." I'm not convinced that
it does - or rather, I think that if it does, it must be buried in
some secondary or tertiary effect. IOW, I think the energy invested
in the vibration is negligible, and/or almost all recovered.

As an analogy, riding a bike on a smooth road with a series of gentle
hills or undulations (say, on a 100 foot wavelength) has the
bike&rider accelerating slightly down hills, then decelerating on the
way back up. But if it weren't for the secondary effect of increased
aero losses on the higher speed portions, there wouldn't be any
significant energy loss caused by the accelerations. And in fact,
those sorts of roads tend to give higher TT speeds, IIRC.

So: more roughness in the drive motion, I agree. Larger bend angle,
therefore a tad more friction loss, I agree. But aside from that, do
you have an explanation of where chordal action causes the energy
actually to leave the system?

- Frank Krygowski

Dear Frank,

Changing the speed of the chain run every time a link engages the
sprocket means accelerating and decelerating the chain run.

Acceleration and deceleration take power.

At 90 RPM on a 53x11, pins are engaging and disengaging on the top run
4770 times per minute. The chain speed change on the front 53 is
0.1976%, but 4.0507% on the 11-tooth rear.

It takes power to speed up and slow down the chain run ~ 4% almost
5,000 times per minute.

Cheers,

Carl Fogel

wrote in message
...
Changing the speed of the chain run every time a link engages the
sprocket means accelerating and decelerating the chain run.

Acceleration and deceleration take power.

At 90 RPM on a 53x11, pins are engaging and disengaging on the top run
4770 times per minute. The chain speed change on the front 53 is
0.1976%, but 4.0507% on the 11-tooth rear.

It takes power to speed up and slow down the chain run ~ 4% almost
5,000 times per minute.

Still - what's the size of the power loss? Are you accelerating and
decelerating ONLY the single link?

Carl Fogel wrote:

Changing the speed of the chain run every time a link engages the
sprocket means accelerating and decelerating the chain run.

Acceleration and deceleration take power.

Don't confuse accelerating and slowing down on a bicycle with
mechanical action and losses. A swinging pendulum accelerates from
standstill to maximum speed every cycle and does so in a vacuum for a
long time, demonstrating that there is no power required.

At 90 RPM on a 53x11, pins are engaging and disengaging on the top
run 4770 times per minute. The chain speed change on the front 53
is 0.1976%, but 4.0507% on the 11-tooth rear.

It takes power to speed up and slow down the chain run ~ 4% almost
5,000 times per minute.

Where does the power go? What power does it take to slow down a
moving chain and where is it extracted from the mechanism?

Jobst Brandt

On Jun 16, 12:14 pm, wrote:


Dear Frank,

Changing the speed of the chain run every time a link engages the
sprocket means accelerating and decelerating the chain run.

Acceleration and deceleration take power.

Acceleration takes power or energy. Deceleration (in this instance)
would give back power or energy.

I'm sure we've previously discussed the idea of a bike with large-mass
wheels, like flywheels, but with the same total mass as a normal
bike. Yes, it takes more energy to accelerate the flywheel bike up to
speed, and it wouldn't be good for sprints. But if you were to point
that bike up a hill, you'd recover your acceleration energy, as it
helped prevent the bike from decelerating. It wouldn't decelerate as
quickly as a normal bike of equal total mass.

A similar industrial application is a stamping press with a large
flywheel driven by a small motor. Energy is stored in the flywheel as
the motor accelerates it up to speed. That energy is given back to
the system when the press is activated and the flywheel decelerates.

I think your chain is doing the same when it's in its deceleration
phase. I don't see that energy being wasted into heat, except for the
previously discussed pin friction during bending.

- Frank Krygowski

On 2008-06-16, wrote:
[...]

It's worth noting that no one has produced a credible test showing a
chain in action transmitting significantly different power when
different lubes are used--most of the power loss is due to chordal
action, the variation in chain speed caused by straight links of chain
suddenly wrapping around the "circle" of a sprocket. That vibration is
why even the motorcycle chains running in sealed oil baths lose around
3% power.

So why does efficiency increase with tension? I suppose a tighter chain
vibrates less.

Thinking of your picture of the "floating" chain, you might think well
you've got to lift that dangling chain up each time it goes onto the
sprocket, but then of course it falls back down giving you the energy
back.

Ben C? wrote:

It's worth noting that no one has produced a credible test showing
a chain in action transmitting significantly different power when
different lubes are used--most of the power loss is due to chordal
action, the variation in chain speed caused by straight links of
chain suddenly wrapping around the "circle" of a sprocket. That
vibration is why even the motorcycle chains running in sealed oil
baths lose around 3% power.

So why does efficiency increase with tension? I suppose a tighter
chain vibrates less.

Thinking of your picture of the "floating" chain, you might think
well you've got to lift that dangling chain up each time it goes
onto the sprocket, but then of course it falls back down giving you
the energy back.

You seem to be using wreck.bike as a thought scratch pad. I notice
there is no question mark or indication of a proposal included. By
airing such dabblings, some readers may take up the thread and build
on it. That seems to be occurring in technology lately.

Jobst Brandt