[CR]Re: Fork Blades

(Example: Framebuilding:Tubing:Falck)

From: <BobHoveyGa@aol.com>
Date: Wed, 24 Dec 2003 13:46:48 EST
To: classicrendezvous@bikelist.org
Subject: [CR]Re: Fork Blades

In a message dated 12/23/03 10:01:40 PM, Tom Sanders writes:

<< As I look at earlier forks I notice they often incorporate a more = extreme bend very low on the fork than we see in more recent forks and, = finally, we see the often straight forks (stilettos?) that are seen on, = say modern Colnagos. The early ones with the extreme bend are more = pleasing to my eye. I suppose this is just a matter of personal taste. I am wondering why the change away from this earlier form? Is there an = improvement associated with a lesser fork bend? Perhaps a weight = savings? Were these earlier ones a more supple ride than later ones = with less of a bend? >>

There was a thread about this on the Framebuilder's list. I seem to remember a consensus that most of the shock absorbtion came not from the bend but from the area near the crown (which I guess makes sense since the area near the fulcrum would be the area of greatest stress). If this argument is correct then I guess the shape of the bend doesn't mean a heck of a lot overall.

As for the reason for differing bends, my guess is that aside from changes in taste and fashion, the most motivating factor would be that by decreasing the radius in favor of a smoother and shallower curve one would create a stronger blade since stresses caused by bending would be decreased. And since the shortest distance between two points is a straight line, I suppose there would be some overall structural benefit as well as some miniscule weight savings. But at what cost... those straight-blade Colnago forks gotta be the ugliest things I've ever seen.

To my eye, the most beautiful bend for a fork blade is a section of a parabola, where the blade begins to curve shortly after leaving the crown but with a barely perceptible radius. Then the radius of the curve progressively decreases as you approach the dropout, resulting in a beautiful smooth curve with absolutely no breaks or awkward spots to stop the flow of the eye as it traces the curve. Since most of the tubes on a bicycle are straight, the only real visual tension and movement in most bikes appears in the fork blades... that's why I've always felt that visually at least, this is one of the most important parts of a bicycle. Whether a bike looks graceful and light or sedate and earthbound often boils down to how the fork was bent!

Bob Hovey
Columbus, GA