Centre Hub Steering, Leading Link Forks & Twin Head Steer
Unorthodox steering arrangements are a recurring theme throughout the history of Feet Forward motorcycles for two main reasons. The engineers involved could see the tortuous load path, from the front wheel to the forks and through the headstock before being fed into the frame. They also saw the inherent limitations of telescopic forks; combining suspension and steering loads in one device (once described as “a triumph of engineering over common sense”).
Centre hub steering uses an inclined king pin in the centre of a large diameter inner hub and the wheel sits on thin large internal diameter bearings on the inner hub. The kingpin is on a shaft that is mounted on a swinging arm connected directly to the frame. Although an excellent arrangement, there are a couple of drawbacks. Firstly the size of the bearings and the arm that hold the kingpin limit the steering lock, brakes were difficult to arrange (until the advent of disc brakes) and they are expensive to make. Jack Difazio developed a workable arrangement which he fitted to a number of machines in the 60s and 70s. Royce Creasey further refined the centre hub steering design, considerably improving the steering lock.
Leading link forks offer some of the advantages of centre hub steering at a fraction of the price. However the main drawbacks are that the load path into the frame is still tortuous and the higher rotational mass that can affect steering.
Twin head steer machines used the telescopic forks of the donor machine but the headstock was heavily modified so it pivoted backwards and forwards. Steering was controlled by drag links connecting the front wheel spindle to a steering arm mounted on the lower part of motorcycle frame.