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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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