Fork construction

The fork is the key element in a Pedersen design, where the paradigm of the diamond frame is really shattered. Instead of the classical fork with two blades hold together to the stem by a bracket, the Pedersen fork consists of a truss construction out of basically four triangles united at the top and reinforced with a central bracket. Instead of a stem supported by bearings in a 10 cm head tube as standard bicycles, the Pedersen fork has two separated fixation points about 35 cm apart, so that the fork is an integral part of the frame structure.




Here is a picture of the Dursley Pedersen factory workers showing the advantages and resistance of a truss construction for the fork. Impressive resistance, and yet lightweight. This picture is a really convincing example of marketing and advertising techniques of the early XXth century.



The construction of the fork and the upper head tube with the frame fixation point is rather complicated and time consuming. It took me more than half of the whole project duration, as I did all tubing miting by hand and using no power tools. Just old fashioned hand filing.

For my fork design I recycled the top stays of the donor bicycle, as you can see in the following picture. This recycled bent tubes were used for the rear fork tubing, along with straight tubing 12mm diameter with 1mm wall thickness for the front tubes. This tubing was of regular quality and I bought it in the nearest hardware store. I did not use for this bike any specialized Columbus tubing, chromoly or anything like that. In the picture below also a prototypical bracket can be seen, along with a recycled lug, the shackle and the lower fixation head.



The first step was to manufacture two fork blades, left and right, with a triangular shape, out of one straight and one bent tube. For the top joint I had to mite the tubing very carefully to an exact match before brazing. The miting can be seen here, and it took much more time than what could be guessed from the picture.



Prepared for brazing, fluxed and ready to go.



A brazing professional would probably describe this as a butcher job rather than a clean joint. However, a solid joint it certainly is.



Here is after cleaning and miting for the upper joint between the two blades. Notice that the miting revealed a very nice layer of brazing filler material at the joining surfaces in the tip. There it is, a sound brazing joint after all.



For the lower side of the triangle I deviced another type of design for joining both tubes, as the lug has to be solidly attached. I turned in the lathe a steel bolt which I brazed to the tip of the rear bent tube. In the tip of the straight tube I filed and shaped the connection to fit the lug. In the picture below, all this can be seen, with the raw brazed joint.



Finally I did mite the steel point at the tip of the bent tube, to meet the straight tube precisely at an angle and prepared the connection for the lug. I did not yet braze the whole assembly with the lug, as I need first to check proper alignment of the wheel within the complete fork.