Rotor Q-Rings and the RD

Aug 27, 2012
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#1
Does anyone have any experience of oval chain rings? I'm intrigured by the Q-rings which make sense to me from a mechanical point of view but I'm still trying to mentally figure out if you are fighting the RD with every half rotation? i.e. you might be more efficient by getting "a larger cog" on the down stroke, but surely your RD spring is being pulled forward at the same time (diminishing the gain)?
Also will that back and forth of the RD for every half rotation of the crank wear it out?
 
Aug 27, 2012
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London, UK
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#3
Thanks Simon.
Well Sheldon addresses my issue,
quoting from the article above "People are often astonished to learn that I ride Biopace chainrings on fixed-gear bikes. They imagine that there will be tremendous changes in chain tension as the chainring rotates. In practice, this is not the case. A 42 tooth chainring will generally engage 21 teeth against 21 chain rollers, regardless of its shape.
There is a slight variation in tension resulting from the varying angle between the two straight runs of chain as the axis of the chainring rotates, but this has not generally been of a sufficient magnitude to cause any problem in practice for me."
That would suggest I am wrong to think the RD would be pulled back and forth by an elliptical front chainring. .....And taking another look at it (10 mins later with elliptical paper cut-outs on my desk proving the point to myself!) I can see how it works without increasing the necessary chain size. The key is that the cog needs to maintain a mirror image of itself at all degrees of rotation.
Anyone out there actually tried them then?
Seems Frome and Wiggins bypassed the Q-rings and went straight to some low volume guy in France whose rings have no pins or helpers for changing gear, but have a more aggressive shape
 
Aug 27, 2012
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#7
Just tried out my new Osymetric chainrings. Post is here:
Many thanks for the post! Very keen to hear more as you use them over the medium term. Did you buy them here in Japan or order direct from the company in France?

If anyone has a BB30 130 BCD crank kicking around (ideally 165-170 arms), please let me know (or knows a cheap new source) - I'd be keen to buy so I can try these.

(BTW My current crank is 110 BCD - doesn't fit)