Fork construction continued

The process of fabricating the fork took nearly a month of patience, miting and brazing. Once both blades were ready the lugs were brazed in place, after careful alignment of the wheel axis.
Here are both fork blades put together with the wheel. The lugs are solidly fixed to the fork and I was satisfied with the resistance of the whole assembly. Note the radial lacing of the front wheel spokes. Anyway, this is a topic for a future post.



The next point was to align the fork and prepare to braze both fork blades together. The upper part of both blades was carefully mited to fit together at a precise angle. This is was can be seen in the next picture. The wheel is assembled in place and centered. Both fork blades are hold together with clamps, cleaned and fluxed.



Neat and solid brazing joint.



This is how the bare fork construction looked like. No bracket or stem yet. I put the mudguard in place to measure the bracket position and dimensions.



For the bracket I used a steel plate with a thickness of 2mm, conveniently bent at 90 degrees, that I found at my standard source place for scrap metal. I started from the very basic specifications for the bracket: I need to hold together 4 fork tubes, to support the articulated joint that connects with the frame and to support the caliper brake and mudguard.

Once the functionality of those features is secured, I proceed with cutting bracket with a design-as-you-go approach unleashing the best of my plastic artist's creativity. In the next picture it can be seen how I carved the holder to braze the nut to fix the articulated joint. The slot for assembling the brakes and mudguard is already done.



Here is the nut in place, fluxed and ready for brazing. Note the carvings I did in the bracket. It took some time, but was a rewarding experience.



Here is the bracket aligned, fluxed and ready for brazing. Below you can see my Sievert torch with a 70 g/h nozzle and a 0,4 kg camping-type butane bottle.



The idea to fix the stem was originally just to mite the inner stem tube to match the four tubes of the upper fork blades. I was concerned that this point where the stem is brazed to both blades, would become the weakest point of the whole construction. After some discussion with my work colleage Peter, he came up with the suggestion of a bolt with cylindrical head brazed to the tip of the fork blades that fits the inner diameter of the stem. This contraption was named the "Boldten" piece, and really reinforced the whole stem assembly considerably. Thanks, Peter!



The stem was recycled from the donor bike. It was necessary to cut out the recessed part where the headset lower bearing was fixed, since the new head tube will have shorter length and different positioning. A new ring for fitting the lower headset bearing will be needed.
Careful miting of the stem inner diameter to match the four tubes of both fork blades can be seen in the next picture.



The stem was solidly brazed in place. Note the small holes in the stem. Their purpose is to access the cylindrical head of the "Boldten" piece for brazing. Now it is evident that the stem is attached to the blades fork construction in two points, increasing the rigidity of the whole structure.



Next step was to manufacture the ring that supports the lower bearing of the headset. This was done in my old trusty Unimat 3 from Austria, as shown below.




Coincidentally, the ring needed to be placed over the holes used for brazing the "Boldten" piece, and therefore, no traces of such holes were left after the ring was brazed in place.