Oval chainrings was Re: [CR]Interesting crank/arms on Ebay

(Example: Production Builders:Peugeot:PX-10LE)

From: "Charlie Young" <youngc@netreach.net>
To: Classicrendezvous@bikelist.org
Subject: Oval chainrings was Re: [CR]Interesting crank/arms on Ebay
Date: Wed, 07 Jan 2004 11:51:33 -0500

Oval chainrings greatly predate the PMP crankarms. For some history and theory, see:

http://www.argonet.co.uk/highpath/cycle_/ovals.htm and http://www.argonet.co.uk/highpath/cycle_/ovtech.htm

I recently acquired a 50t Ovum chainring. 144mm BCD with 10 evenly spaced mounting bolt holes to allow different amounts of crank advance or retard (in coarse 36 degree increments!). Ovality is pretty high at ~27%. Based on the information from Highpath, I'll be trying 0 degrees retard/advance from the minor axis.

Anyone else have experience with the Ovum chainring or knowledge of when they came on the scene? A PMP contemporary?

Highpath indicates that ovality should be less than 10% for fixed gears and less than 15% for hubgears. I know Dan Artley has his Thetic on his JT w/ ASC. Dan: what is the ovality of the Thetic, any chain drops, and how much retard are you using.

thanks, Charlie "only Biopace experience so far" Young Honeybrook, PA

Richard noted:
> At around the same time, there was a company selling an
> oval shaped chain ring that was supposed to do the same
> thing. I've never seen a bike built with either one. Has
> anybody on the list any experience with that oval 'ring?
> I would think there would be shifting issues...to say the
> least! Richard Reno
> Green Bay (wind chills of -15F) Wisconsin