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#11
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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 |
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#12
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Chain skipping under load(for no obvious reason)
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 |
#14
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Chain skipping under load(for no obvious reason)
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 |
#15
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Chain skipping under load(for no obvious reason)
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. |
#16
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Chain skipping under load(for no obvious reason)
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 |
#17
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Chain skipping under load(for no obvious reason)
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#18
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Chain skipping under load(for no obvious reason)
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 |
#19
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Chain skipping under load(for no obvious reason)
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 |
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