Motorcycle front suspension
The annoyance of the rigid fastening of the wheels in the frame, caused by the increasing weight and speed of motorcycles, and also the poor condition of the roads of that time, She forced” on designers the need to solve this problem. It started with the front one, the steered wheel, the vibrations of which had an adverse effect on driving safety. Much has arisen, more or less successful designs of the front suspension, in which almost all possible types of spring elements were used, i.e.: coil springs, flat springs, rubber bundles, and even compressed air.
The so-called. suspension with swing fork, invented in England and taken over by other European companies. In this design, the arms of the front fork were two parallel triangles (made of thin pipes), attached with the apex – facing the longest side - to the bottom of the head tube, rotary, on the horizontal axis. The lower vertices of both triangles were the places where the front wheel axle was mounted, in the upper ones, a coil spring mounted on the central pin limited the fork deflection. This construction was simple and cheap, however, she had this inconvenience, that the spring deflection caused by the fork movement was accompanied by a change in the wheelbase, the result was a deteriorated stability of the motorcycle. The swinging fork was therefore suitable for not very fast motorcycles.
Another of the more famous designs was the Webb front fork, invented by an English motorcycle parts manufacturer. In this solution, apart from one central spring (working in compression) Lever friction shock absorbers are used on both sides of the fork. Webb's fork was characterized by great stiffness and torsion resistance. Velocette companies used it among the best-known producers, Rudge Whitworth, Guzzi motorcycles, Motosacoche i inne.
The fork with an extension spring was structurally similar. As the name suggests, the main difference was that the spring was mounted differently (it was stretched during the operation of the suspension). Soon, the fork's triangular tubular structure was replaced with stamped sheet metal elements.
The swinging fork underwent further design modifications - the so-called. trapezoidal suspension (based on the principle of a parallelogram with a central spring) used e.g.. in Puch motorcycles, Norton, Zundapp. On some motorcycles (Levis, FN, etc.) springs (squeezed) were placed on the sides of the fork, which facilitated their replacement in case of damage.
The work of an English constructor – Brough's fork was known as the Castle, in which the front wheel was suspended on a short pusher arm, built (partly) from tubular elements, falling into each other telescopically. The role of the suspension was performed by compressed and extended springs, placed in a telescopic cover. Castle fork was used by Brough Superior and Harley-Davidson.
In the front leaf spring suspension, the rigid front fork was connected to the wheel by short trailing wishbones. The shocks from the wheels were transferred to the front end of the quarter-elliptical leaf spring with special vertical rods., the other end of which was connected to the head tube. This construction was introduced for the first time by the Indian company, soon it was also used in ABC vehicles, Megola, BMW and others.
Several companies are applying for the authorship of the telescopic front fork. At the beginning of the 20th century, we meet him, e.g, in Scott motorcycles, UN and BMW. In the design of BMW, it was possible to significantly reduce the unsprung weight of the motorcycle. An oil shock absorber was also placed concentrically with the coil spring. All the moving parts of the fork were wetted with oil, which in combination with the closed structure of the telescope ensured their lower wear. This design was soon used by all major motorcycle manufacturers.