Page 31 - PBCOctober2019

Pickwick Bicycle Club Magazine Volume 16 No.2 October 2019 !31

And now for something different……continues

We resume Willie Tonkin’s story of - The Bike Game, which
began in the March magazine and was left at a critical stage of frame construction:

Now the assembled tubes on the set up board are beginning to look like a bike frame, the
joints are fluxed and pinned. The chainstays are now cut to length, mitred and assembled
into the bottom bracket shell, and the ends located on a spindle on the board. At this
stage you take the measurement from the spindle to the seat lug bolt hole. The frame can
now be un-clamped from the set up board, the joints fluxed and pinned and the back
stretcher bar added.
The stretcher bar is a telescopic jig with the top part locating in the seat lug ears. The
bottom part consists of a rear hub spindle complete with cones and wing nuts, set at right
angles to the telescopic tube and the spindle is fitted into the centre of the rear end
slots. This is set to the measurement taken while the frame was on the set up board. The
purpose of this is to support the chain stays while the bottom bracket is being brazed,
Otherwise as the bottom bracket gets red hot the unsupported chainstays would droop
and you would lose the bottom bracket height, and could also distort the bottom bracket
shell.
The builder would first hold the frame up to eye level and make sure the seat tube is in
line with the head tube, as while the frame is only pinned it can easily be adjusted by
twisting before brazing. The forge is basically a metal tray measuring about four by two
feet and perhaps four inches deep. This tray is filled with coke or asbestos cubes and odd
bits of fire brick and a nest is made to surround the back of the bottom bracket which is
the next joint to be brazed.
When I first started building, the forge was heated by a pair of foot bellows and air
was mixed with coal gas in the torch. With your foot on the bellows you had wonderful
control of the amount of heat you applied to the joint. Soon it became red hot and you
would apply the brass rod, keeping the joint wet with flux. Suddenly you would see the
whole joint momentarily go black as the molten brass flows between the bottom bracket
tube outlets and the tubes. You would probably have to apply the brass strip in two or
three places to ensure complete sealing of all the joints. The bottom bracket soon heats
up again and that’s the job done. The frame is then moved round in the forge and the top
head lug brazed and then the seat lug, and that is the main joints brazed.
While the frame is cooling down the builder will turn his attention to the forks. By now
he knows the length of the head tube and by allowing an extra one and three eighths of an
inch for the head bearings he can cut the fork column to length. A front hub spindle with
cones and wing nuts is fitted in the fork ends to hold the fork blades to the right width