Chassis design

The frame of the FWS1000 was typical of the TT-F1 era. It is a wide perimeter twin loop ‘diamond’ style made from steel tube. Constructing a replica from the available photos seems a straightforward enough process until you begin to delve into the intricacies of motorcycle chassis design.

There are many aspects to consider in the design including basic dimensions like rake, trail, weight bias and wheelbase. Fortunately, the Japanese RACERS magazine vol. 10 featured the Honda V4 line of racing bikes and included a specification table with a number of handy dimensions.

The FWS1000 raced with a 16” front and 18” rear wheel combination. Our replica will use 17” wheels front and rear so we have to consider how that will affect the geometry of the chassis and suspension as well some practical issues like front tyre to engine clearance etc. One critical piece of information is knowing where the centre of gravity is located. When you don’t have a physical object to measure the best you can do is estimate where it is. It’s important to know because it has a direct bearing on rear suspension squat behaviour and where to locate the swingarm pivot in relation to the engine’s output shaft.

So along with some help from Tony Foale and John Bradley and a healthy dose of the ol’ suck it and see approach, it was time to start drawing.

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