Re: [CR] Why no Quick Releases on Track bikes (veering further OT)

(Example: Racing:Roger de Vlaeminck)

From: "Jerry Prigmore" <robinjer@hotmail.com>
To: classicrendezvous@bikelist.org
Subject: Re: [CR] Why no Quick Releases on Track bikes (veering further OT)
Date: Tue, 08 May 2007 16:59:36 -0700



>
>Date: Tue, 08 May 2007 17:48:04 -0400
>From: genediggs(AT)aol.com
>
>...Velodrome racing puts much more stress on the bike frame than you do in
>the average road race. You just can't get the torque level required to
>keep from pulling the rear wheel, on a standing start, with a quick
>release cam mechanism....
>

I respectfully disagree.

Assuming equal-length crankarms, the smaller the chainring, the greater the mechanical advantage applying said pulling force to the chain and rear wheel. Smaller gear = more force. (The size of the rear cog affects the torque applied to the wheel [larger cog = more torque], but doesn't affect to as great an extent the force attempting to pull the drive side of the wheel forward in the fork end). The typically longer cranks on a road bike would further increase the mechanical advantage.

Sprinting up a steep hill on a road bike in the small ring would apply more pulling force to a rear wheel than would sprinting on the track. It may be counterintuitive, but it is simple physics. I can't address the difference in power applied by a beefy track sprinter versus a wispy grimpeur.

The cam action of a properly closed QR can apply an enormous closing force, and unlike a nut, will not loosen, due to the over-center action of the cam. However, "properly closed" is key, so it might make sense for a velodrome official to ban QRs to be on the safe side. At least in a litigious society accustomed to acommodating the lowest common denominator, that is.

Jerry Prigmore
Clovis, California, USA