king@kestrel.ARPA (10/14/85)
Can anyone comment on elliptical chainwheels? I wonder about deurailler wear with one of those, since I understand your mechanism would flex twice every revolution. -dick
eirik@tekchips.UUCP (Eirik Fuller) (10/16/85)
In article <1836@kestrel.ARPA> king@kestrel.ARPA writes: > >Can anyone comment on elliptical chainwheels? > >I wonder about deurailler wear with one of those, since I understand >your mechanism would flex twice every revolution. > >-dick I have never held one in my hand, but I've seen one up close, in action. Surprisingly, the derailleur pulleys move only during shifts. (I never did get around to formulating a mathematical proof of this, but I've seen it happen). Needless to say, a front derailleur is out of the question, though the same is not true of Biopace chainwheels, the 'other' odd-shaped chainwheels. By the way, I have wanted an elliptical chainwheel for some time. Is there anybody out there who knows where I can get one to fit a TA bolt circle (five holes, very close together)? I want one for my Hypercycle, which has no front derailleur anyway. (It has a crossover gearing setup with two chains, two rear derailleurs, and twenty-five speeds). Not to be too picky, but about 40 teeth would be nice. I've been too lazy to write to Durham to ask if they make them anymore.
wagner@uw-june (Dave Wagner) (10/18/85)
> >Can anyone comment on elliptical chainwheels? > > > >I wonder about deurailler wear with one of those, since I understand > >your mechanism would flex twice every revolution. > > I have never held one in my hand, but I've seen one up close, in > action. Surprisingly, the derailleur pulleys move only during > shifts. (I never did get around to formulating a mathematical proof > of this, but I've seen it happen). It seems rather obvious to me, that at any point in time the chain is wrapped around exactly half of the teeth on the chainwheel, regardless of its orientation. Think about it. Dave Wagner University of Washington Comp Sci Department wagner@washington.arpa {ihnp4,decvax,ucbvax}!uw-beaver!uw-wally!wagner "The surest thing there is is we are riders, And though none too successful at it, guiders, Through everything presented, land and tide And now the very air, of what we ride." - Frost
craig@hp-pcd.UUCP (craig) (10/24/85)
I suggest that you watch the rear derailer on a Biopace equipted bike because it does move.