The Forks

After ordering the replacement rear dropouts on a guaranteed next day service i was slightly annoyed when they had not been delivered yesterday so today i set about the only task left that can be completed without them, the forks.

Feeling slightly better after 2 nights of savage flu sweating, shivering and aching this morning and despite the disappointment of the parts not arriving i felt inspired to achieve something tangible on this day of rest. The first task, as always, was to construct another jig very similar to the one that i have built for the rear triangle. After this was done i measured the drop from the break boss to the top of the axle on an existing bike and used this dimension to work out the length and then to cut the two fork blades to this value, there is very little margin for error when cutting to length so it is always a slightly nerve racking experience, especially when two tubes are having to be cut to exactly the same! If i were to build frames frequently a band saw would be an excellent investment but for a one off it would have been an extravagance so i have had to cut all tubes by hand with a rotary tool. After the tubes were cut to length everything was cleaned and fluxed before slotting everything together and placing it in the jig. Once in the jig adjustments were made to give the forks a rake of 61mm (the distance the axle is in front of a virtual line drawn from the centre of the headtube) and an OLD (Over Locknut Dimension, i.e. the hub width) of 123mm, the OLD of the hub will be 120mm but a few extra mm are added for ease of insertion.The next task was the brazing, you may notice the different colour of the fluxs used on the crown and the dropouts. As i have mentioned in previous posts bronze is more suited to filling larger gaps than silver and as there was a fair bit of play in the crown i decided to use bronze for this component and go back to silver for the dropouts, the flux used for bronze brazing is pink, that which is used for silver is white.

Brazing done and after a bit of a clean up the forks are almost completed.
A close up of the dropouts:
A close up of the crown:
A fair bit of grinding down of the excess bronze will be required here as i used my standard approach for the forks of masses of excess guarantees a strong joint!

There is still quite a bit of work left to do before they are completed, firstly as you can see i left the steer tube slightly long when brazing it into the crown, i did this because it makes it easier to see when the brazing alloy has flowed all the way through the joint, this needs to be ground down level with the crown. Then a hole needs to be drilled through the crown and tapped (threaded) so that a break can be bolted on to it. Finally it will need to be polished up with the brass wire wheel along with all of the other joints when it arrives...

The frame as it currently stands:


P.S. I have noticed what i am sure will become an annoying rattle in one of the fork blades, some of the excess broze must have formed a bead and dropped into the blade whilst brazing, oh well!