I asked Bill Gray about this process when he was still active as a frame
repairer in the late 90's. He explained that the decorative element started
life as a 1/16th gauge stamping from flat sheet steel. The stamping was then
curved to form a tube shape or "sleeve" . This was then tacked to the frame
tube - using a steel welding rod and the oxy acetylene process. This bi
laminate assembly was then mitred to fit, be it head tube, bracket shell or
seat tube. The frame was then bronze welded using oxy acetylene and bronze
filler rods.
Bill had worked at Claud Butlers since 1932. I have recently spoken to
Charlie Ralph of Alves Cycles. He knew Len Hart quite well. Len started at
Gillotts just after the war and specialised in building lugless and Bi lam
frames. Gillotts' L'Atlantique lugless was launched in 1948. He taught Ron
Cooper this process and Ron tells me he was building lugless Bi-Lam Fleur de
Lis frames at Gillott's as early as 1952. Len then went on to teach builders
at Dawes, noted for their lugless King Pin shopper folder. (Dawes also
offered a lugless lightweight with chromed Faux lugs which were wrapped
around the head tube once the frame had been painted. ) Len also worked at
Trustys, of Viscount and Lambert fame, again all lugless as far as I know.
Len told Charlie that the key was the angle at which the torch was held. The
flame should not be pointed directly at the pool of bronze but to the side
so that the radiated heat is doing the melting. A good man could lay a
continuous fillet of bronze so smooth and even that no filing was required.
Mark Stevens in delightfully warm Dingwall, Scotland