The bicycle curves

The bike's top tube required a curve. So that the grain of the wood followed the curve this meant bending. I planned to saw wood into thin strips that would bend when dry then glue them back together whilst clamping them in a form. It soon became apparent that because the bike's top tube is not only curved but also tapering from the head tube to the seat tube I was in danger of getting short lengths and glue lines showing if I made the strips of wood parellel. After much thought and tweaking I decided that the strips needed to taper. I didn't want to to end up with many very thin strips so in the end I settled on five, tapering from 13mm down to 9mm. I did a quick trial on some scraps and found these were still fairly hefty sections for bending dry around the required curve. I soaked some section and found them much easier to bend, but still not quite as easy as I wanted. After much thought I decided I would do a trial of steam bending the sections and leave them clamped but unglued long enough for them to assume the curve. I would then unclamp them and reclamp them, glued. My hope was that the steam bending will leave the strips so close to shape that once glued they will not be under much stress. I had steam bent timber before, but had recently spotted a steam bending trick from a boat builder, which I was keen to try. The picture below shows my propossed timber layout.

bike curve layout

 

© Christopher Thompson