fork blade dimensions: oval, round
 

I have done a bit of internet searching and come up with a range of numbers for what I thought was just 2 styles of Classic oval steel fork blades. By this I mean the cross-section of the blade, measured at the top where it fits into (or onto) a fork crown.
Leaving off the really old "D" shaped blades, up till now I thought there was a
Reynolds "Imperial Oval" (longer and thinner) and a
Columbus "Continental Oval" (shorter and fatter)

Now I find a wider range of names and sizes (all mm), could there be this much variety or variation out of the factories, or is it because of sloppy (inconsistent) measuring?

Very early Reynolds 531 blade................................. 30 x 12.5
Reynolds 'A' blade: stamped 30 x 17, measured...... 29 x 16
Reynolds 531 "Imperial" (but sometimes called CO) 28.5 x 16.5
Reynolds 531 "Continental Oval"...............................29 x 16
Columbus "Continental" standard blade....................28 x 19
Reynolds 531 NCO (NEW Continental Oval).............27.5 x 20



Since I'm making a list, here's some round (Pista) blade dimensions
Reynolds (531?).........................................................22
Columbus SP..............................................................24

Please clarify or add more mud to the waters.:twitchy:

Cool, I like this. Ihave nothing to add at the moment (I'm in my office, where my only bike is my folding bike, which has an aluminum fork, so I won't trouble you with its measurements) but will try to check a couple bikes later on.

To be clear, when you say 'oval' you really mean 'elliptical', correct?

I was working on fork with round blades the other day and noticed the dimensions of the two blades did not seem to be identical. They are circa '55 Reynolds 531. Would point to inconsistency if my observation is correct. I'll measure and report back

I'm not a mathematician, so just using the term that is in common usage: Reynolds (and some fork crown makers like Vagner and Haden) call the shape an "oval".
Haden labels the original cross-section "Continental Oval" and the later version "New Continental Oval", which is what Reynolds and Raleigh (who first adopted that blade for the Team Pro) called it (NCO).
I'll have to look up Columbus specs but they probably call theirs "ovale" or maybe "ellittica".

Edit: according to my Columbus catalog, the term they use is "ovale ellittico" and they translate it as "elliptical oval" in English.
They have a very consistent dimension throughout the entire line: 28 x 19 (from SL down to Zeta) but interesting to see that the Round forkblade is offered in 24mm (SP) and a smaller 22.2mm (PL, the lighter gauge set).

Brought this up to my frame building friend today, he said, " of course the dimensions are different after assembly, they've been cut according to the builds layout". So are you measuring unused fork blades or fork blades already built up?

actually I am not measuring anything myself, just reporting the published dimensions from various sources.
I'm sure there could be slight changes in the dimension if a blade is greatly cut down (into the area where it tapers) but from what I see the typical blade has a large enough untapered top end such that a range of forks could be cut (from say a 27" to a 650C) and still have the same dimensions at the tops.
I'm also sure that a blade top can be "massaged" a little to fit a given fork crown...probably was done all the time.
The Haden catalog blurb says that the crown opening of theirs for the NCO Reynolds (27.5 x 20) is also "suitable for other similar blades from other manufacturers" which has to mean that a Columbus (28 x 19) can be made to fit in that oval hole...just squish the end a little.

I'm going by memory, but I seem to recall that my Maasi has 26 mm round blades.

do you know whether it's Columbus, Reynolds or some other brand fork blade?

Yup. In fact, Reynolds' "Continental oval" and "Imperial oval" blades started out as the same round tube (aka "track fork blade"); they're just pressed into slightly different oval shapes. It's trivial to squish a Continental oval blade to fit an Imperial oval crown (but I've never tried the other way).