Thursday, August 20, 2009

# of gears in i-motion 9, thoughts

Make & Model Range 1st 2nd 3rd 4th 5th 6th 7th 8th 9th

Sram i-Motion 9 340% 0.54 0.62 0.73 0.85 1 1.17 1.38 1.61 1.84
D: THAT'S the secret the SRAM rep wouldn't tell me?!
It's what I thought it'd be.

The percent hop between gears is pretty choppy.
Compare to the Rohloff, with uniform steps.
plus .09, plus .11, plus .15, plus .15...
Not ideal, but likely tolerable.
It does mean going above/below personal preference on cadence.
It means mid-range, one must spin-out with too high a cadence for comfort prior to switching.


I probably listed this last year, but this is a frickin' terrific article!

Point is that the devil is in the details.
If yer out of yer cadence but in an ideal gear, the result is similar to in yer cadence but in a less-than-ideal gear.

Weight versus Drag.
A fairing pays for itself- at speed.
Uphill it is a bugger.
Then there is cross-wind.

If I build a fairing-less cycle with commuting in mind, the gearing simply will NOT be what I need for a road tour with a fairing.
The gearing for commuting can be midrange, and mid-level gear hub will suffice.
I don't have alotta weight or severe hills for low gearing.
I will just coast downhill, and won't be racing, so no high gearing either.
BUT put this cycle on a road tour with a ruck sack, after a day (or week) of steady cycling, and the demands are extreme.

I mentioned my Mark I, and contrasted it with the FB Green Machine.
Well oddly I can make up the weight penalty of the Schlumf Mountaindrive.
(I'd go to a larger chaingring for the default gear hub arrangement on the road tour.)
I can offset the weight via an industrial toothed belt.
The whole thing is sealed, so other than ambient humidity, there are no environmental considerations.

D: basic primer on gear hubs.


OK just one question.
Why for the love of god?
This is a damn penny-and-farthing.
It'd creep along at, what, 10kph tops?

Now tack a Rohloff hub where the pedals go, and Bob's yer uncle!
No idea how to attach it.

You listening, big impersonal unreactive corporation?

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