Chain skipping under load(for no obvious reason)

dabac wrote:

Sheldon's site has that listed as doable. Without sending off
to a metallurgy lab I'm as certain I can be that I'm running
the new chain on the previously unused sides of the teeth. Not
that there was much wear on the other side either.

The wear doesn't need to be visible to the eye for a new chain
to skip. In the past, I've found some chains to be more prone
to skipping than others. I remember Wippermans circa 1980 as
being particularly sensitive to any sprocket wear.

Back then, putting a new Shimano or DID chain on would sometimes
eliminate the skipping.

John

John Henderson wrote:

Sheldon's site has that listed as doable. Without sending off to a
metallurgy lab I'm as certain I can be that I'm running the new
chain on the previously unused sides of the teeth. Not that there
was much wear on the other side either.

The wear doesn't need to be visible to the eye for a new chain to
skip. In the past, I've found some chains to be more prone to
skipping than others. I remember Wipperman chains circa 1980 as being
particularly sensitive to any sprocket wear.

Visible is probably inaccurate because looking at a chain, one cannot
readily see the dimension critical to skipping, which is pitch
elongation. If you hold a ruler next to the chain matching an inch
mark with the center of a link pin, one foot away the % out of pitch
is "visible" by the mismatch in twelve inches of chain. 1/8" = 1%.

Back then, putting a new Shimano or DID chain on would sometimes
eliminate the skipping.

New chains skip better than worn chains because they do not mesh with
worn driven sprockets while at the same time they work on worn CWs.

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

Jobst Brandt

wrote:

John Henderson wrote:

Sheldon's site has that listed as doable. Without sending
off to a metallurgy lab I'm as certain I can be that I'm
running the new
chain on the previously unused sides of the teeth. Not that
there was much wear on the other side either.

The wear doesn't need to be visible to the eye for a new
chain to
skip. In the past, I've found some chains to be more prone
to
skipping than others. I remember Wipperman chains circa 1980
as being particularly sensitive to any sprocket wear.

Visible is probably inaccurate because looking at a chain, one
cannot readily see the dimension critical to skipping, which
is pitch
elongation. If you hold a ruler next to the chain matching an
inch mark with the center of a link pin, one foot away the %
out of pitch
is "visible" by the mismatch in twelve inches of chain. 1/8"
= 1%.

Back then, putting a new Shimano or DID chain on would
sometimes eliminate the skipping.

New chains skip better than worn chains because they do not
mesh with worn driven sprockets while at the same time they
work on worn CWs.

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

Yes, and the last time you and I discussed my observation that a
new brand A chain could skip when a new brand B one didn't, we
failed to find an explanation.

John

John Henderson wrote:
wrote:

John Henderson wrote:

Sheldon's site has that listed as doable. Without sending
off to a metallurgy lab I'm as certain I can be that I'm
running the new
chain on the previously unused sides of the teeth. Not that
there was much wear on the other side either.
The wear doesn't need to be visible to the eye for a new
chain to
skip. In the past, I've found some chains to be more prone
to
skipping than others. I remember Wipperman chains circa 1980
as being particularly sensitive to any sprocket wear.
Visible is probably inaccurate because looking at a chain, one
cannot readily see the dimension critical to skipping, which
is pitch
elongation. If you hold a ruler next to the chain matching an
inch mark with the center of a link pin, one foot away the %
out of pitch
is "visible" by the mismatch in twelve inches of chain. 1/8"
= 1%.

Back then, putting a new Shimano or DID chain on would
sometimes eliminate the skipping.
New chains skip better than worn chains because they do not
mesh with worn driven sprockets while at the same time they
work on worn CWs.

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

Yes, and the last time you and I discussed my observation that a
new brand A chain could skip when a new brand B one didn't, we
failed to find an explanation.

John


Some chains have more play between the rollers and the sleeves of the
innerplates. That could be an explanation.

Lou

On Apr 2, 2:19*pm, Lou Holtman wrote:
John Henderson wrote:
wrote:

John Henderson wrote:

Sheldon's site has that listed as doable. *Without sending
off to a metallurgy lab I'm as certain I can be that I'm
running the new
chain on the previously unused sides of the teeth. *Not that
there was much wear on the other side either.
The wear doesn't need to be visible to the eye for a new
chain to
skip. *In the past, I've found some chains to be more prone
to
skipping than others. *I remember Wipperman chains circa 1980
as being particularly sensitive to any sprocket wear.
Visible is probably inaccurate because looking at a chain, one
cannot readily see the dimension critical to skipping, which
is pitch
elongation. *If you hold a ruler next to the chain matching an
inch mark with the center of a link pin, one foot away the %
out of pitch
is "visible" by the mismatch in twelve inches of chain. *1/8"
= 1%.

Back then, putting a new Shimano or DID chain on would
sometimes eliminate the skipping.
New chains skip better than worn chains because they do not
mesh with worn driven sprockets while at the same time they
work on worn CWs.

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

Yes, and the last time you and I discussed my observation that a
new brand A chain could skip when a new brand B one didn't, we
failed to find an explanation.

John

Some chains have more play between the rollers and the sleeves of the
innerplates. That could be an explanation.

Although we have been spanked in the past for such statements because
the relevant distance is pin to pin and not roller to roller (at least
in terms of wear measurements). -- Jay Beattie.

Turning sprockets around to the "unworn side" is a misnomer. Although
when an elongated chain runs on driven sprockets doing most of its
wear on the loaded face of teeth, wear also occurs the unloaded face
because it bears on these as it engages. Inspecting sprocket that has
been run with a badly worn chain will reveal the backs of teeth as
shiny and worn.

Jobst Brandt

Wrote:
..Inspecting sprocket that has
been run with a badly worn chain will reveal the backs of teeth as
shiny and worn.

If I put one "reversed" sprocket on top of a "original orientation"
sprocket and only line up on two teeth and the valley between them there
is no visible shape distorsion at all to my eyes.
The sprockets have some sort of surface treatment that's slightly
grayer than gun black and in a matte finish. When I look on the
previously front slopes these have acquired a metallic sheen while the
previously rear slopes still has the same lustre as the sides of the
sprockets. I maintain that wear is minimal.

I've gone over the chain again, and it appears fine. No stiff or
twisted links. There may be something wrong with the quicklink, it feels
a bit too loose sideways, as if it's meant for a wider chain.
Now, if only there'd been some sense of rhytm to when the chain skipped
I'd been quite pleased with that find...
It also appears as although seemingly symmetrical when viewed from the
side the sprockets may not be symmetrical when viewed from the rear, the
biggest and smallest appear to have a bevel ground into them,
determining their direction of rotation. This might well be a
contributing factor to the issues I'm having, although IMO this still
doesn't fully explain why it runs so smoothly w/o load and so poorly
under load. I'd have imagined seeing at least some skipping or
hesitation during the bench runs if this was the cause.


--
dabac

dabac wrote:

I've gone over the chain again, and it appears fine. No stiff
or twisted links. There may be something wrong with the
quicklink, it feels a bit too loose sideways, as if it's meant
for a wider chain. Now, if only there'd been some sense of
rhytm to when the chain skipped I'd been quite pleased with
that find... It also appears as although seemingly symmetrical
when viewed from the side the sprockets may not be symmetrical
when viewed from the rear, the biggest and smallest appear to
have a bevel ground into them, determining their direction of
rotation. This might well be a contributing factor to the
issues I'm having, although IMO this still doesn't fully
explain why it runs so smoothly w/o load and so poorly under
load. I'd have imagined seeing at least some skipping or
hesitation during the bench runs if this was the cause.

The dynamics of chain skipping on the driven sprocket are such
that the skipping will occur only under load. Without
considerable force holding rollers into the slight recesses in
the tooth profile, there's no obstacle to the chain feeding
smoothly onto the sprocket in the area where they come together
into mesh.

John

Took the sprockets off yesterday, gave them all another good look,
flipped over, laid together and compared tooth flanks back and forth.
Only visible difference is the (originally) backwards facing corners on
the top of teeth on the biggest sprockets, which seems to be chipped.

Reassembled in the original orientation(the one with the visible
surface wear), went for a ride. Smallest procket skips when out of the
saddle, but as long as I remain seated it's as smooth as anything.
biggest sprocket skipping gone entirely.

I guess the cynics had it right with: "no good deed goes unpunished".
I really thought I was doing a sensible thing when I flipped the
sprockets over before bringing this hub into service again.
New rim, new spokes, new chain, new bike, and a new set of tooth flanks
to wear on - made sense to me.

Hopefully the return to the original orientation will keep the bike
behaving long enough for me to get the summer bike together. Then I'll
have something to ride while I decide how to graft a Shimano body onto
this hub and hopefully get it done before winter and the need for
studded tires returns.


--
dabac