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OBree uses a slack chain



 
 
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Old September 15th 09, 08:09 PM posted to rec.bicycles.tech,rec.bicycles.racing
Fred Fredburger[_6_]
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Posts: 29
Default OBree uses a slack chain

Howard Kveck wrote:
In article ,
"Tom Kunich" wrote:

"Ryan Cousineau" wrote in message
]...
In article ,
Howard Kveck wrote:
(This is completely distinct from the lateral chainline
that Tom Kunich brought up, which is irrelevant to
variations in chainslack, and it should be possible to
get chainline aligned to 1mm or better, otherwise you
risk chain-throwing, which is No Fun on a fixed gear.)
Having a chain at an angle will cause some mechanical loss but it's
ridiculously easy to get the chain line on the money. TK's comment
("By all means explain to us how you can perfectly align a chain line.
Most especially on a home-made chainring.")

One of the reasons that I've put these fools on :ignore" is their willful
stupidity. For instance, all you have to do is look down at your chainring
when you're riding to see it wobbling back and forth when you're turning the
cranks. This is a combination of the alignment of the rings on the cranks
and the bearing play and the setup play in the mechanism.


Willful stupidity, huh? Where to begin...

Bearing play? Setup play in the mechanism? Sorry but neither of those has anything
to do with wobbly chainrings. The rings in most cases are made from stamped
sheetmetal (no real guarantee of flatness there), with the outer edge thinned on a
lathe. If the gear blank is not flat after stamping then the thinned section will
follow that non-flatness.

But guess what? All it takes is a simple prybar and you can ease your chainrings
into spinning perfectly true side to side. Not that hard.

As long as it doesn't exceed moderate values it doesn't hurt a thing but you
DO have to take it into account.

And this despite not even mentioning using an old lath possibly with bad
bearings to cut your own chainwheels.


Why assume bad bearings? The most likely reason for wobble on a lathe is less than
optimal fixturing (i.e. chucks not mountied perfectly or fixture plates not indicated
in). there's no reason to think that Obree doesn't know how to set up his stuff to
work perfectly, old lathe or not. He has given every indication in the past that he
is very knowledgeable and a perfectionist.

The end result is that the chain tends to wander back and forth on the
chainrings as you ride. This is part of the source of the inefficiencies and
drag of the chain/chainring drive mechanism.

What's more, Howard knows all this as well or better than I do since he
works with this sort of stuff every day as a machinist.


It's great that you acknowledge that I may possibly know more about machining than
when you. But when you start off with "One of the reasons that I've put these fools
on :ignore" is their willful stupidity" while responding indirectly to something I
posted makes it sound as if you think I'm disagreeing with you even though I should
know better, that I'm arguing against what I may have learned in a long career as a
machinist. No, Tom: I'm disagreeing with you because the things you're saying are not
supported by what I've learned in a long career as a machinist.

And you've again done a cowardly thing. You responded critically to someone you
have killfiled indirectly (via responding to that person's argument that you read in
someone else's post). You aren't planning to have a discussion with that person
because you can't read their response. That is pure cowardice.


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