Re: [CR] twin-plated fork crowns

(Example: Component Manufacturers:Cinelli)

In-Reply-To: <BE19A021.38F9%fatticbicycles@qtm.net>
References:
Date: Sun, 23 Jan 2005 19:57:26 -0800
To: classicrendezvous@bikelist.org
From: "Jan Heine" <heine93@earthlink.net>
Subject: Re: [CR] twin-plated fork crowns


Twin-plate fork crowns

Doug Fattic wrote:
>They really are lighter, I just weighed some from my
>framebuilding supplies to make sure.

Indeed, most bikes in the French technical trials had twin-plate crowns, even if the makers usually did not use them on customer's bikes.

One question I have is how well these crowns can deal with twisting of the fork blades from brazed-on brake pivots - canti or even more pronounced with centerpulls, where the pivot is brazed close to the crown, with little blade to "absorb" the flexing motion each time the brake is applied. Obviously, this twisting action would stress the lower plate more than the upper one and might lead to failure. Thoughts?

I wonder whether this is the reason most French constructeurs did not use twin-plate crowns on their production bikes after World War II. In the 1930s, they were found on many bikes, including tandems. The fact that they switched from a lighter to a heavier crown on their production bikes can't have been cost, so there must have been a functional issue.

--
Jan Heine, Seattle
Editor/Publisher
Vintage Bicycle Quarterly
c/o Il Vecchio Bicycles
140 Lakeside Ave, Ste. C
Seattle WA 98122
http://www.mindspring.com/~heine/bikesite/bikesite/