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Old 06-17-09, 06:01 PM   #1
Contour
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A single adjustable gear?

Last night I was thinking of idea's to simplify the gearing of a bike. I came up with a concept of a single adjustable gear. After thinking and doing a little research today I found this which appears to my cover my concept. Now my question has a design like this or the concept actually ever been implemented into any bikes (custom or otherwise). Are there flaws with the concept or that design in particular that I may be over looking? Also what do you think of the concept, assuming there was a design that could implement it well.
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Old 06-17-09, 06:37 PM   #2
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I don't know about it, but an IGH is a much better solution, and you can get a nice one for a pretty good price.
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Old 06-17-09, 06:46 PM   #3
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To clarify, this isn't so much about the other options rather this particular concept and how it may be implicated.
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Old 06-17-09, 06:49 PM   #4
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There is Truvativ's hammershmidt.
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Old 06-17-09, 07:19 PM   #5
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One gear is better.

FIX your bike.
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Old 06-17-09, 07:53 PM   #6
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Expanding chainwheels have been invented a lot of times. The problem is that a bike's chain tension is so great that a mechanism that can change the effective chainwheel size while standing up to the stress winds up being very heavy. The book to read if you're interested about all the crazy things that have been tried for bicycle gearing is "the Dancing Chain" by Frank Berto.
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Old 06-17-09, 10:24 PM   #7
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i forget what the name is but there is a company in sandiego that just came out with an infinite gear hub. they make the transmissions for ford hybrids. its really trippy to ride.
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Old 06-17-09, 10:40 PM   #8
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i forget what the name is but there is a company in sandiego that just came out with an infinite gear hub. they make the transmissions for ford hybrids. its really trippy to ride.
Nuvinci: http://www.fallbrooktech.com/Nuvinci.asp
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Old 06-18-09, 12:14 AM   #9
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snips out of The Dancing Chain...
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Old 06-18-09, 01:05 AM   #10
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i rode a nuvinci equipped bike at interbike. it's a pretty cool system but somewhere else on the board some said the the nuvinci hub weighs 9 pounds. when i picked up the bike it sure felt like that is true.
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Old 06-18-09, 01:59 AM   #11
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Are we trying to reinvent the wheel again?
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Old 06-18-09, 09:29 AM   #12
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snips out of The Dancing Chain...
As noted it has been invented and tried again and again. Some have even made it to market briefly I believe. None have succeeded. Problems have been weight and complexity as well as having moving parts subject to dirt and wear due to the high loads involved. Remember that at the chainwheel the mechanism has to withstand the full torque of a standing rider while a geared hub has that reduced by the primary drive ratio, normally at least 2 to 1. That reduces torque loads by half or more for the IGH.

Interesting bike transmission concepts are well covered in "The Dancing Chain" as well as in the second and third editions of "Bicycling Science" published by MIT. I have the recently published third edition of "The Dancing Chain" and can highly recommend it. It is available from Amazon for less than 2/3 the list price. If more bike drivetrain "inventors" read the books then they would save a lot of skull sweat
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Old 06-18-09, 09:57 AM   #13
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Thanks for all the replies and suggestions. I'll definitely check out the Dancing Chain book and the Bicycling Science one as well.
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Old 06-18-09, 05:01 PM   #14
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Trek actually did some research in this area and came out with theoretically infinite gear stepping It was belt driven so it probably wouldn't be included in "The Dancing Chain" haha. But I found an entire bike with this setup selling for all of $300 3 or so years ago. I guess since there is not much market for something this exotic, only a collector would buy it. The mechanics of it appeared to take up a good half of the center of the wheel and weigh probably 15 pounds. At this point in time, anything you would gain in performance you would loose in servicability and complexity.
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Old 06-18-09, 05:05 PM   #15
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Eliminate the chainwheel and go drive shaft
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Old 06-18-09, 05:22 PM   #16
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Quote:
Originally Posted by zzzwillzzz View Post
i rode a nuvinci equipped bike at interbike. it's a pretty cool system but somewhere else on the board some said the the nuvinci hub weighs 9 pounds. when i picked up the bike it sure felt like that is true.
I was wondering how heavy a thing like that would be. 9 pounds for the rear hub alone is about 30-40% of the typical cruiser weight. Add that on top of the bike weight. Oh, well, you'll get your exercise riding this thing!
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Old 06-18-09, 05:26 PM   #17
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Eliminate the chainwheel and go drive shaft
Driveshafts are 10-15% less efficent at transmitting energy than chains are.
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Old 06-18-09, 05:26 PM   #18
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You can always install a rat in a exercise wheel, and vary your speed by adjusting his feed?
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Old 06-18-09, 05:36 PM   #19
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I.e. vary his amphetamine drip rate. And spare rats are cheap and fairly light.
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Old 06-18-09, 07:48 PM   #20
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Quote:
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Eliminate the chainwheel and go drive shaft
It's been done, starting in the 1890's.

Heavy, mechanically inefficient and, for more than one gear, it's only usable with internal geared hubs which add their own level of inefficency.
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