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MOTORCYCLE FRAME Filed June 4. 1968 3 Sheets-Shee'l'. 3
United States Patent O 3,508,765 MOTORCYCLE FRAME Stefan George Bauer` Hilton, Bernard Hooper, Stourbridge, and Robert Victor Trigg, Birmingham, England, assignors to Norton Villiers Limited, Wolverhampton, Staffordshire County, England, a British company Filed June 4, 1968, Ser. No. 734,312 Claims priority, application Great Britain, June 7, 1967, 26,254/ 67 Int. Cl. B62k 1]/02 U.S. 'Cl. 280-281 10 Claims ABSTRACT OF THE DISCLOSURE The disclosure describes motorcycle frames each of which has a straight tubular backbone which is triangulated with two pairs of straight tubes, one tube of each pair being on each side of the backbone and the tubes being connected to attachment means at the rear end, and intermediate the ends, of the backbone.
BACKGROUND OF THE INVENTION Field of the invention The invention relates to motorcycle frames. By motorcycle are included all mechanically powered, twowheeled vehicles which are steerable and thus we include in the term motorcycles proper, scooters and mopeds.
Description of the prior art A great number of constructions have been proposed for motorcycle frames and a great many of these proposed constructions use bent tubes which are required to take considerable bending moments when the machine is in use. In some frames, for example, there are two com plete loops which are arranged side by side and are interconnected.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a simple frame in which bending moments which are generated in a main member or backbone due to the dynamic loading on the frame when it is in use are transferred into tensions or compressions in two further pairs of tubes which are triangulated with the main member. These further tubes therefore actsubstantially as pure ties or struts.
According to the invention we -provide a motorcycle frame comprising a straight tubular backbone, a support for the front forks of the motorcycle secured to the front end of the backbone, rst and second transversely-extending rigid attachment means secured to the backbone adjacent its rear end and intermediate its ends respectively said means projecting on both sides of the backbone, a first pair of spaced-apart, substantially parallel tubes -extending generally downwardly from, and secured to, said rst means and a second pair of spaced-apart substantially parallel tubes inclined relative to the backbone and extending rearwardly from, and secured to, said second means the tubes of each pair being arranged one on either side of the backbone, the tubes lying to one side of the backbone being joined and the tubes lying to the other side of the backbone being joined, all said tubes being straight between their junctions and the attachment means.
By this construction, the backbone is triangulated with the two pairs of tubes and since these tubes are straight within the triangulation at least, they act purely aS struts or ties and do not have to take any appreciable bending moment. Preferably, the moment of inertia of 3,508,765 Patented Apr. 28, 1970 ice the section of the backbone is considerably greater than the moments of inertia of the sections of the other tubes.
Preferably, there is provided third, transversely-extending, rigid attachment means secured to the backbone to project on both sides thereof and located between the rst and second attachment means and a third pair of tubes, which is extended between the first and third attachment means, the backbone being interposed between the tubes of the third pair.
The first attachment means may comprise a plate secured to the backbone and lying in a plane substantially perpendicular to the longitudinal axis thereof. In this construction, the upper ends of the tubes of the rst pair are secured to the edges of the plate which lie in generally vertical planes.
The tubes of the rst and second pairs preferably either support other tubes, or the tubes of at least one of said pairs are continued, to form a generally U-shaped cradle between said support and said junctions. The limbs of the cradle will be of unequal length, the longer limbs extending so said support. This cradle will carry the power unit of the motorcycle which maycomprise an engine and gear box in unit or connected together.
The second attachment means may comprise curved continuations of the tubes of the second pair, said continuations having their ends connected directly to the backbone and being reinforced by gussets to'form a rigid assembly. In this construction, although each tube of the second pair will have a curved portion, this curver portion will not be able to ex and is considered to be part of the rigid attachment means because it is braced to the backtion between the first attachment and the tubes of the first pair.
