RE: [CR] Was: Woodrup frames. Now: BB height, etc.

(Example: Framebuilding)

Date: Mon, 01 Jan 2007 12:51:29 -0500
To: <classicrendezvous@bikelist.org>
From: "John Betmanis" <johnb@oxford.net>
Subject: RE: [CR] Was: Woodrup frames. Now: BB height, etc.
In-Reply-To: <000b01c72d5f$3bed02c0$6401a8c0@maincomputer>
References: <3.0.6.32.20061231231243.00880100@mailhost.oxford.net>


I was trying to figure out how to answer that without getting any deeper into something I can't readily back up with numbers, but couldn't really come up with anything. I guess it depends on what is perceived as "stability" and at what speed. A unicycle's wheel isn't turning fast enough for much gyroscopic effect and there's no trail or steering head angle, so it's all balance, or broomstick effect. My Jeunet track bike with 11" BB height feels just as stable as my Nishiki road bikes with 10.5" so I think it's a combination geometry and gyro effect depending on speed. No doubt a lower BB and saddle also also contributes to confidence for many folks.

At 11:42 PM 12/31/06 -0500, Ken Freeman wrote:
>Not quite agreed here. I accept the claimns that a low BB aids cornering,
>but the effect of moment of inertia does not go away while the bike is
>rolling. It ceases to be the only force with influence, but it doesn't go
>away. True, it is the only force involved during a trackstand, ignoring
>wind.
>
>Are you saying gyroscopic forces become dominant? Do you have any numbers
>to support that?
>
>Ken Freeman

John Betmanis
Woodstock, Ontario
Canada