Before I get started let me show you where the magic begins. Here are some shots from Timberline, the sweetshop for woodworkers. Here you can pick wood from an incredible range of colours, grains and textures.
The frame uses Padauk, a rich red coloured and fairly dense African hardwood, Sycamore Maple, a European cousin of the Maple tree that we tend to call Sycamore and Ovangkol, a beatifully grained, dense African hardwood, similar in apperance to Walnut. These are all have the right properties for a well performing frame.
The frame design differs from the Single Speed in several ways. The most notable is the monster downtube and the rear stays. These were both modified to increase lateral frame stiffness at the bottom bracket. The down tube is 50% deeper but 40% thinner, which has increased torsional stiffness by around 30% while maintaining a similar tube weight. As described in …., torsional stiffness of the down tube is key to a stiff frame. The rear stays have been lowered down the seat tube, this does 2 things. Firstly, it reduces the length of the stay to give it more lateral stiffness without having to make it heavier, secondly it reduces the frontal area of the stays to make them more aerodynamic.
In general, the tubes have all been made significantly thinner (2mm in places) but have been increased in diameter where extra stiffness is needed. The end goal was to make a sub 2kg frame that maintains the stiffness and performance of a top end carbon frame.
Internal stiffeners have been built into the tubes to counteract the reduced ‘dent resistance’ caused by making them thinner. A lot of research went into this small step!
The design work was all carried out in Rhino based on a parametric model built in Grasshopper. This let me tweak every aspect of the geometry as many times as I wanted untill I was happy with the design. All dimensions were parametarised including centreline geometry, tube sizes, chamfer radii and tube thicknesses.
The original plan was to get the frame CNC routed to the 3d model file, however, with several quotes in excess of £500 I decided to make it by hand…… a long but theraputic exercise!