Saturday, August 29, 2009

sram i-motion 9 thoughts




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D: I stand corrected.
The gears shift at a regular rate throughout most of its range.
The % change per gear is a bit more than the Rohloff.
D: I cannot figure out how that one store I mentioned can be so cheap.
I think they only have 3 in stock, and must be dumping it.

The fan sites say the chainring to cog tooth ratio must be 1.7-1.9

If I were to use this with an industrial belt, I'd want to keep the torque on the belt down.
However, with a fixed chainline and ? a series of track bike chains strung together ? the torque limit of the gear hub is the only issue.

IZUMI ECO Gold Track Chain. $23.95. Premium 1/8 " gold plated track chain. ... Weight: 277.0 g; Compatible with Shimano 10-speed drive trains [more] ..

D: OK so a chain of say 10' length on a 'bent would weigh, what, 3x that?
about a kg.

Recumbents use standard bicycle chain times two or three — sometimes more. ...

http://www.sheldonbrown.com/nanodrive/index.html
Hmm. narrow 1/2 weight nanodrive.

That was all back before anybody who matters was even born, and now it's time for the first 21st century drive train: "Nanodrive/Quarter-Twenty." This new modern universal standard cuts every dimension of a traditional chain in half! 1/4" (6.35 mm) pitch, with sprockets just 3/64" (1.19 mm) thick. In addition to cutting the weight of your chain and chainwheels in half, it also lets you fit twice as many sprockets as the old fashioned systems!

Mechanical Aspects

Although the new system has 20 rear sprockets instead of only 10, they fit in the same space, since everything is half the thickness of the old junk! Thus, they'll work with any standard frame.

The only parts you need to replace are the rear wheel, the front derailer, the rear derailer, the cassette, the crankset and chainrings, and the shifters! Nothing to it!

(from http://www.sheldonbrown.com/nanodrive/index.html)

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D: my lousy Paint pic is a revision.
Gawd I must learn Google Sketchup !

Anyway, as you can see, this addresses clearance on the front wheel with a series of cog adjustments to vary the belt line.
This is to address the idea of a one-size-fits-all industrial belt mod to work on 'bents.
It is a worth a pound or two in weight savings.

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