Something rarely considered is the types of roads used for bike races BITD. Much of the infrastructure of Europe was destroyed during WWII. Most of the western European economies didn't fully recover until the early 1970's! Nice smooth road surfaces were not a high priority plus many early season races like the Paris-Roubaix and other events in northwest Europe were held on cobblestone roads.
During the US Bike Boom Fad, "10 Speed Racing Bike" was the buzzword. Most of the lower priced European bikes copied the frame geometry that was popular on the "racing bikes" used during the 1960's that were made for rough road surfaces. That meant relaxed head and seat tube angles, long wheelbases, especially the rear triangle and a long fork rake with most of the bend in the lower 1/3rd of the blade.
Here's an extreme example one type of fork blades offered by Reynolds. Fork blades act as springs for the front of a bike!
I used 2 1/2" rake fork blades on my long wheelbase touring frame that I build for myself in 1975 using 1950's geometry. It can go over a speed bump and I hardly feel it!
Reynolds offered 8 different fork blade designs in a 1950's tubing catalog. Note, Rake No. 3--2" and Rake No. 6--1 1/4" with the graceful slow taper bends were probably intended for use on track or time trial bikes - mostly with round blades.
Most pre-bent fork blades were shaped by hand like in this photo taken at Reynolds in the 1970's. This probably made for lots of variances depending on how many pints were consumed at lunch!
Columbus, Super Vitus and the Japanese brand tube sets came with straight blades. When I was first starting to build frames in 1975 I tried using one of these Rigid electrical conduit benders. I scrapped a number of blades before we had someone build us a jig that we could bend both blades in a brazed fork at the same time.
Some folks used something like this crude home made fixture frequently with a wooden form instead of this bent angle iron.
This is a very sophisticated commercial fork bender made by Anvil that bends both blades at the same time.
My late 60's early 70's Galmozzi built Lazzaretti with classic road bike geometry from the era: long wheel base and rake with 73° angles.
By the end of the bike boom in 1973 a lot of Italian frame makers were building frames with geometry that had previously been used for track bikes only: short wheelbases and fork rakes with 74° angles. Top Italian builders like Masi an DeRosa were putting out forks with a beautiful, graceful bend that started at the fork ends and went all the way to the crown. Ron Cooper in the UK was a proponent of that style too.
1970's Masi Gran Criterium.
Creating those bends takes a lot more effort than just starting 2/3rds of the way down the blade. Slow taper fork blades became De rigueur on better bikes and frames into the mid-late 80's but not many took the bend all the way to the top. There is a slight trade off with those style blades in that they are going to be less shock absorbing than blades with a rake lower down in an area with a smaller diameter.
verktyg