Sidecar - Design

Design

A sidecar motorcycle is a three-wheeled vehicle with the side wheel not directly aligned with the rear motorcycle wheel, and is usually powered by the rear wheel only. This is different from a motor tricycle (trike), where both rear wheels are powered and share a common axle. However, either P.V. Mokharov of the Soviet Union or H.P. Baughn of Great Britain seem to have to been the first to employ a driven sidecar wheel in 1929. Baughn two-wheel-drive outfits were so successful in trials events in the early 1930s that there were attempts to have the ACU ban them from competition. A great many companies experimented with two-wheel drive in sporting events and indeed many companies employed them in military vehicles prior to the commencement of WWII. Currently, the Russian manufacturer Ural produces several models with two-wheel drive that can be engaged as desired.

The sidecar consists of a frame (which originally was rigidly fixed to the motorcycle's frame on one side and is supported by the sidecar's wheel on the other side) and of a body. The body typically provides one passenger seat and a small trunk compartment behind. In some case the sidecar has a removable soft top. In some modifications the sidecar's body is used for carrying cargo or tools, like a truck's platform). The sidecar is typically mounted so that the motorcycle is closer to the center of the road, i.e. with the sidecar on the right for right-hand traffic.

A sidecar makes the handling of a bike asymmetrical. Without a brake on the non-driven sidecar wheel, the sidecar will pull towards the bike under braking, and towards the sidecar under acceleration. While a sidecar pilot is described as driving rather than riding, with all but the heaviest rigs, the comparison to a car is weak. Driver and passenger body position affect higher speed handling, especially on dirt or other uneven surfaces. If the sidecar and bike geometry are not coordinated the combination will be unstable, especially at speed, with shimmy upon acceleration or deceleration.

The motorcycle's steering geometry, originally set up for a tilting single track vehicle, is set up to turn slightly away from the drag imposed by the sidecar. Leaning the motorcycle by clamping it rigidly a few degrees opposite the sidecar is used, along with a few degrees of "toe-in" of the sidecar wheel toward the centerline of the vehicle, is used to provide a balance resulting in comfortable, straight line travel. Most sidecars are also fitted with steering damping devices, of either friction or hydraulic type, to lessen the effects of sudden inputs, as encountered on rough roads, upon the vehicle's handling. Another issue, particularly with bicycle sidecar outfits is the problem of applying side-thrust to light-weight components only intended and built to resist radial forces.