broken chain on a fixed gear

On 31 Jan 2006 06:30:35 -0800, "autopi"
wrote:

sorry, the URL should read:

http://tinyurl.com/cyrjx

Still broken. Is this perhaps posted on a machine that's only visible
from within the network at Northwestern? The error comes back that
pubweb.nwu.edu cannot be found. Being behind a campus firewall might
cause that.

btw, it sounds like it might have been the chain derailing--though i
don't know what would have caused *that*. i hadn't mucked with the
wheel, chain, anything in probably 9 mos. or so, and i've only had it
derail one other time in the year and a half i've had the bike. it
happened on a flat, straight section of road, nothing in particular
stands out as being unusual...

Sounds like the chainline may be a bit off, and the chain may have had
a bit too much slack. Also, check for bent or clipped teeth on both
sprockets.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

ok, this is getting silly...i don't know why the photos aren't coming
up. let's try these:

http://www.freeimagehosting.net/aa8fdb754f.jpg

and

http://www.freeimagehosting.net/adb7e8616d.jpg

i'll double check the chainline and the cogs tonight--thanks for the
advice! (and yeah, i meant "chain" not cable--it was getting late last
night...)

On 31 Jan 2006 11:03:30 -0800, "autopi"
wrote:

ok, this is getting silly...i don't know why the photos aren't coming
up. let's try these:

http://www.freeimagehosting.net/aa8fdb754f.jpg

and

http://www.freeimagehosting.net/adb7e8616d.jpg

i'll double check the chainline and the cogs tonight--thanks for the
advice! (and yeah, i meant "chain" not cable--it was getting late last
night...)

Looking at the edges of the inner sideplates, I think I see chewed
spots that would indicate that there's a chainline and/or slack
problem at the root of the failure, as more or less expected. Looks
like the chain could have used a drop or two of lube, too.
Metal-to-metal without lube can make it much easier for a tooth to
grab a link's sideplate and walk it up.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

...less-than-perfectly-orthogonal angle...

I think I once knew the meaning of orthogonal. If I did, I've long
since forgotten. In any case, isn't the pin supposed to be driven in
perfectly perpendicular to the plates? Which I don't think is
orthogonal, is it?

Did anyone else notice the rat chewing marks @ the 4th from the bottom
pin's roller and general vicinity? I doubt that could come from one
derailing event. My guess is repeated pounding on teeth caused by chain
or cog warpage or poor chain line.

For a simple & clear explanation of chain line measurement see "Zinn &
the Art of ... Bike Maintenance"

Now that Ma Po addled brain has had a little time to think about it,
isn't orthogonal the way pipe spool drawings are done in power plants,
refineries, etc? And the orientation of the po abused chain in the
photograph?

Best Wishes, John

On Wed, 01 Feb 2006 22:22:21 -0800, john wrote:

...less-than-perfectly-orthogonal angle...

I think I once knew the meaning of orthogonal. If I did, I've long
since forgotten. In any case, isn't the pin supposed to be driven in
perfectly perpendicular to the plates? Which I don't think is
orthogonal, is it?

Yes it is; they are synonyms.

Did anyone else notice the rat chewing marks @ the 4th from the bottom
pin's roller and general vicinity? I doubt that could come from one
derailing event. My guess is repeated pounding on teeth caused by chain
or cog warpage or poor chain line.

I just looked at the pic. That chain has clearly seen a lot of abuse, and
not much if any lubrication. But those rat-chewing marks might just be
grime, in a funny light.

--

David L. Johnson

__o | It is probably that television drama of high caliber and
_`\(,_ | produced by first-rate artists will materially raise the level
(_)/ (_) | of dramatic taste in the nation. -- David Sarnoff, 1939