RE: [CR]Fork Crowns, continuation of Fork Blade discussion

(Example: Framebuilding:Norris Lockley)

Subject: RE: [CR]Fork Crowns, continuation of Fork Blade discussion
Date: Fri, 5 Aug 2005 08:13:38 -0700
Content-class: urn:content-classes:message
Thread-Topic: [CR]Fork Crowns, continuation of Fork Blade discussion
Thread-Index: AcWZxtVc9My7ODKXT0OA/3VkRTdKTQAB37dA
From: "Mark Bulgier" <Mark@bulgier.net>
To: "classic list" <Classicrendezvous@bikelist.org>


John Thompson wrote:
>
> Fork blades are essentially identical to chainstays (except
> 24mm track blades, of course) that have been ovalized and
> raked. Socketed crowns were available for a variety ovals,
> but a little judicious work with a vice can usually convert
> one type of blade oval to another.

I think John is talking about adjusting the blades to fit the crown to adjust for the small differences between brands, but within the same basic size.

I haven't been able to adapt blades to the "wrong" crown, if we're talking between the old Reynolds skinny "Continental" oval and the Columbus oval (Reynolds's "New Continental").

The problem is not just the degree of ovalization but the bulk size - the old skinny oval starts life as a 23mm round tube, where the Columbus starts as a 24 mm round. (Chainstays, back in the CR era, were 22.2 mm and quite non-interchangeable with any fork blades.)

If you make the old skinny oval less oval, it's too small, by enough that filling the gap with brass isn't really acceptable.

Squashing a Columbus to the flatter oval leaves it too big to fit a crown made for old Reynolds blades, though you can often grind out some metal from the socket of the crown using a rotary file or burr on a die-grinder. Too much work, except for occasional one-offs, and it can leave the wall of the crown socket too thin.

(I'm talking here about regular socket crowns that fit over the blade - the internal type crown that goes inside the blade has the converse problem.)

Mark Bulgier
Seattle WA, USA