weighted oil

Quoted message said:

When I used to battle with off road motorcycle chains (to keep them lubricated), the process that
lasted the longest was to melt axle grease into a fluid and dip the chain in it.

why didn't you use an o-ring sealed chain? they're expensive, but perfect for off-road applications.

[email hidden] (john cop) wrote in message
news:<[email hidden]>...

Quoted message said:

If you look in any engineering book about oil lubrication in bushings, the theory is that a film
of oil is "pumped" into area between the axle and bushing by the relative rotation of the two
parts. The friction in a properly set up system like this is just the shear in the oil. The axle
should never be in contact with bushing (gas engines self-destruct when this happens - although
car engines apply pressure with an oil pump but the idea is the same). Obviously, too little or
too light an oil will result in a very small contact area with a high contact stress between the
axle and bushing which generally results in higher friction with a siezed bearing or relatively
rapid wear. It would also suggest that a chain lubricated with a light oil might have very low
friction with little load and high friction once a big load was applied.

Your description of what's in "any engineering book" has little relation to chain lubrication.

You've described fully floating lubrication, which can be achieved only with a continuously spinning
shaft. That's because it takes some time for that internally-produced film of oil to develop enough
internal pressure to "float" the shaft away from the bushing. Intermittent rotation won't allow this
floating action.

Instead, the pins and bushings of a bike chain see action closer to that of a door hinge. It's a
"boundary lubrication" situation. You can't prevent metal-to-metal contact. All you can do is keep
the contact relatively slippery.

Quoted message said:

When I used to battle with off road motorcycle chains (to keep them lubricated), the process that
lasted the longest was to melt axle grease into a fluid and dip the chain in it.

I always thought it was silly for motorcycles to have their chains out in the open. Why subject them
to the road grime? If protected by an enclosed chain case, they'd probably last ten times as long.

As it is, my motorcycle's an old BMW. Shaft drive, no worries.

- Frank Krygowski

Frank Krygowski said:

Instead, the pins and bushings of a bike chain see action closer to that of a door hinge. It's a
"boundary lubrication" situation. You can't prevent metal-to-metal contact. All you can do is keep
the contact relatively slippery.

Even in bounbdry layer lubrication there need be no metal to metal contact and in a chain there
probably isn't or it would weld and tear out streamers of metal. Liquids behave as fluids only in
bulk. In mono-layers as in boundary layer lubrication, liquids (oil) behave like more like solids
and cannot be squeezed out of an interface. If this were not the case, ball and roller bearings
would not work at all.

If you consider the shape and pressure in a ball to race interface, no liquid would remain there if
it were able to flow. In fact, oil remains between ball and race as wee see in long term service of
ball bearings lubricated by oil leaching from a grease in most electric motors that serve many
years of running. In contrast, static ball bearings fail from fretting, in which, even under light
loading balls and races weld after lubrication has been displaced by micro motions between ball and
race. This is the failure mode of bicycle head bearings that bear the lightest loads of any bearing
in a bicycle.

Quoted message said:

Quoted message said:

When I used to battle with off road motorcycle chains (to keep them lubricated), the process that
lasted the longest was to melt axle grease into a fluid and dip the chain in it.

Quoted message said:

I always thought it was silly for motorcycles to have their chains out in the open. Why subject
them to the road grime? If protected by an enclosed chain case, they'd probably last ten times
as long.

Bicycle chain wear is almost exclusively a function of grit contamination and all the esoteric
lubrication rituals have marginal effect on that. The exception is excessive or repeated oil
lubrication of a dirty chain that accelerates grit contamination.

Jobst Brandt [email hidden]

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

Quoted message said:

Even in bounbdry layer lubrication there need be no metal to metal contact and in a chain there
probably isn't or it would weld and tear out streamers of metal. Liquids behave as fluids only in
bulk. In mono-layers as in boundary layer lubrication, liquids (oil) behave like more like solids
and cannot be squeezed out of an interface. If this were not the case, ball and roller bearings
would not work at all.

If you consider the shape and pressure in a ball to race interface, no liquid would remain there
if it were able to flow. In fact, oil remains between ball and race as wee see in long term
service of ball bearings lubricated by oil leaching from a grease in most electric motors that
serve many years of running. In contrast, static ball bearings fail from fretting, in which, even
under light loading balls and races weld after lubrication has been displaced by micro motions
between ball and race. This is the failure mode of bicycle head bearings that bear the lightest
loads of any bearing in a bicycle.

Are you sure this isn't also the failure mode in the interfacing parts of a chain? Seems to me the
action is much the same, although much less extreme. That is, less extreme in terms of pressure at
the contact surfaces and percentage of a given link's life spend under that sort of load. But I
wonder if chain wear might be a very slow fretting failure.

- Frank Krygowski

Frank Krygowski said:

Quoted message said:

Even in boundary layer lubrication there need be no metal to metal contact and in a chain there
probably isn't or it would weld and tear out streamers of metal. Liquids behave as fluids only in
bulk. In mono-layers as in boundary layer lubrication, liquids (oil) behave like more like solids
and cannot be squeezed out of an interface. If this were not the case, ball and roller bearings
would not work at all.

Quoted message said:

Quoted message said:

If you consider the shape and pressure in a ball to race interface, no liquid would remain there
if it were able to flow. In fact, oil remains between ball and race as wee see in long term
service of ball bearings lubricated by oil leaching from a grease in most electric motors that
serve many years of running. In contrast, static ball bearings fail from fretting, in which, even
under light loading balls and races weld after lubrication has been displaced by micro motions
between ball and race. This is the failure mode of bicycle head bearings that bear the lightest
loads of any bearing in a bicycle.

Quoted message said:

Are you sure this isn't also the failure mode in the interfacing parts of a chain? Seems to me the
action is much the same, although much less extreme. That is, less extreme in terms of pressure at
the contact surfaces and percentage of a given link's life spend under that sort of load. But I
wonder if chain wear might be a very slow fretting failure.

Fretting damage occurs where there is insufficient motion for oil to re-enter the interface as in a
ball bearing in which balls do not move enough to expose the race contact spot in oscillatory
motion. This is typical in steering bearing where a vehicle moves straight ahead at high speed, the
speed serving to prevent any steering motions large enough to cause ball contacts to be replenished
with lubricant.

I don't think a chin of any type comes into this mode unless its sprocket is essentially not moving
but with a vibrating load cycle.

Jobst Brandt [email hidden]