[CR]re: Eliptical / Oval? chainring question

Example: Framebuilders:Mario Confente
To: classic list <Classicrendezvous@bikelist.org>
From: "Roy H. Drinkwater" <roydrink@ptd.net>
Subject: [CR]re: Eliptical / Oval? chainring question
Date: Fri, 6 Dec 2002 19:49:25 -0500

Steven Maasland posted:
>I don't have any direct experience with such chainrings but it strikes me as
>rather odd to put an elliptical chainring on a fixed gear. It would seem to
>me that this is an invitation to throw the chain. Perhaps the ellipse is
>small enough that the ideal chain length at the largest and smallest part of
>the ellipse do not vary sufficiently to allow for chain slack?! Personally,
>I wouldn't put anything other than a perfectly round and aligned chainring
>on a fix (or on the timing chain of a tandem) because of the possible dire
>consequences of a thrown chain.
>Hopefully somebody else has more immediate knowledge.

Sheldon Brown stated that he uses Biopace chainrings on some of his fixed gear bikes. I've tried it, and never thrown the chain, but getting the correct tension is very difficult.

Roy "sat with Lou and Richie at the Cirque" Drinkwater Lititz, "& dawn ride with Lou and Karen" PA