GB1567774A

GB1567774A - Motorcycles

Info

Publication number: GB1567774A
Application number: GB2260676A
Authority: GB
Original assignee: RHIND TUTT C
Current assignee: RHIND TUTT C
Priority date: 1977-04-27
Filing date: 1977-04-27
Publication date: 1980-05-21

Description

(54) IMPROVEMENTS IN OR RELATING TO MOTORCYCLES (71) I, CHARLES NORMAN RHIND Turn, of The Bungalow, Berwick St. James, Stapleford, Salisbury, Wiltshire, a British Subject, trading as WASP MO-rORCYCLES, of South Newton, Salisbury, Wiltshire, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to motorcycles.

As used herein, the term "endless chain drive" is intended to include similar forms of hiper kinematic pairs such as belt (particularly toothed belt) and rope drives.

Furthermore, as used herein, the term "sprocket" is intended to include mechanical equivalents, such as pulleys and toothed wheels.

The invention may be advantageously applied to the "competition" type of motorcycle, used over rough country. Present designs of endless chain drives for competition-type motorcycles subject the chain to substantial stress and it is an object of the present invention to reduce that stress.

According to the invention, a motorcycle comprises a frame, an engine and gearbox assembly attached to the frame in a non-pivotable manner, and an endless chain drive comprising a first sprocket rotatable about a first axis, a second sprocket rotatable about a second axis corresponding to the axis of the rear wheel, said first and second axes being disposed a fixedAis- tance apart from each other and also disposed substantially parallel to each other, a single endless chain extending around the first and second sprockets whereby rotation of the first sprocket results in corresponding rotation of the second sprocket and thus the rear wheel, and means interconnecting the frame and the second sprocket so as to support the second sprocket in a resilient manner and whereby its axis can swing about the first axis.

An embodiment of the invention will now be described, by way of example only, with reference to the semi-diagrammatic drawings accompanying the Provisional Specification, wherein: Figure 1 is a fragmentary side view of the rear part of a competition motor cycle and illustrates a known form of endless chain drive and rear wheel suspension system, Figure 2 is a fragmentary side view illustrating a motorcycle according to the invention, Figure 3 is a fragmentary plan view (with parts removed), of the motorcycle of Figure 2, and Figure 4 is a fragmentary plan view illustrating a modification of the motorcycle shown in Figures 2 and 3.

In the Figures, like reference numerals refer to like components.

Referring first to Figure 1, a competitiontype motorcycle 1 is provided with an engine and gearbox assembly 10 attached to a frame 11 in a non-pivotable manner. The rear tyred wheel 2 of the motorcycle 1 is driven by a chain drive 3 comprising a first sprocket 4 rotatable about a first axis 5, a second sprocket 6 rotatable about a second axis 7, the first and second axes 5, 7 being disposed apart and substantially parallel to each other, and an endless roller chain 8 extending around the first and second sprockets 4, 6. It will be apparent that rotation of the first sprocket 4 results in corresponding rotation of the second sprocket 6.

The first sprocket 4 is mounted on the output shaft 9 of the gearbox 10 of the motorcycle 1.

The second sprocket 6 is mounted, in a co-axial manner, at one end of the rear wheel hub 15, so as to be in alignment with the first sprocket 4. The hub 15, which is mounted on an axle 12, is supported in a fork 16 which can swing about an axis 17 defined by spigots (not shown) extending laterally from the sides of the engine and gearbox assembly 10 and located by bushes (not shown) carried by the fork 16. The fork 16 has a cross-member 18. The ends of the axle 12 are located by bushes 13, (See Figure 3).

Swinging movement of the rear wheel 2 is resiled and damped by a pair of telescopic damper springs 19, pivotally attached to an extension 20 of the frame 11. A spring 19 is disposed on each side of the wheel 2 and the end of the extension rod 21 of each spring 19 is attached to the adjacent end of a swinging fork 16. The means 19/21 thus interconnect the frame 11 and second sprocket 6 so as to support the sprocket 6 in a resilient manner and whereby its axis 7 can swing about the first axis 5.

As the motorcycle 1 is driven over rough ground, the fork 16 swings about the axis 17. This movement of the fork 16 is restrained by the springs 19, but nevertheless imposes considerable tension variation on the endless chain 8 as it moves over the sprockets 4 and 6. This variation can result in breakage of the chain.

With reference now to Figures 2 and 3, in the chain drive 3a according to the invention, with which the motorcycle 1 is now provided, the swinging fork 16a (and hence the second axis 7) now swings (as indicated by the double-headed arrow 25), about the first axis 5. This arrangement substantially reduces variation in tension in the endless chain 8 as it passes over the sprockets 4, 6, and thus reduces the risk of chain breakage.

As shown in Figure 3, the swinging fork 16a incorporates ball-races 26 mounted on the ends of the gearbox main shaft 9a, which shaft now extends outwardly from both sides of the engine and gearbox assembly 10.

In the modification shown in Figure 4, the swinging fork 16a is located by inwardlyextending spigots 30 carried by supports 31 fixed to the sides of the engine and gearbox assembly 10. The spigots 30 have a common axis with the gearbox main axis, namely the first axis 5. This modification avoids the need for the gearbox main shaft 9 to be extended through both sides of the assembly WHAT I CLAIM IS: 1. A motorcycle comprising a frame, an engine and gearbox assembly attached to the frame in a non-pivotable manner, and an endless chain drive comprising a first sprocket rotatable about a first axis, a second sprocket rotatable about a second axis corresponding to the axis of the rear wheel, said first and second axes being disposed a fixed distance apart from each other and also disposed substantially parallel to each other, a single endless chain extending around the first and second sprockets whereby rotation of the first sprocket results in corresponding rotation of the second sprocket and thus the rear wheel, and means interconnecting the frame and the second sprocket so as to support the second sprocket in a resilient manner and whereby its axis can swing about the first axis.

2. A motorcycle as claimed in Claim 1, wherein the first sprocket is rotatable by a shaft and the motorcycle is provided with fork means supporting the second sprocket whereby its axis can swing about the first axis, said fork means being pivotally supported by said shaft.

3. A motorcycle as claimed in Claim 1, provided with fork means supporting the second sprocket whereby its axis swings about the first axis, said fork means being pivotally supported by the engine and gearbox assembly by spigot means.

4. A motorcycle substantially as hereinbefore described with reference to Figures 2 and 3 of the drawings accompanying the Provisional Specification.

5. A motorcycle substantially as hereinbefore described with reference to Figures 2 and 3 of the drawings accompanying the Provisional Specification, modified substantially as hereinbefore described with reference to Figure 4 of said drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Swinging movement of the rear wheel 2 is resiled and damped by a pair of telescopic damper springs 19, pivotally attached to an extension 20 of the frame 11. A spring 19 is disposed on each side of the wheel 2 and the end of the extension rod 21 of each spring 19 is attached to the adjacent end of a swinging fork 16. The means 19/21 thus interconnect the frame 11 and second sprocket 6 so as to support the sprocket 6 in a resilient manner and whereby its axis 7 can swing about the first axis 5.

As the motorcycle 1 is driven over rough ground, the fork 16 swings about the axis 17. This movement of the fork 16 is restrained by the springs 19, but nevertheless imposes considerable tension variation on the endless chain 8 as it moves over the sprockets 4 and 6. This variation can result in breakage of the chain.

With reference now to Figures 2 and 3, in the chain drive 3a according to the invention, with which the motorcycle 1 is now provided, the swinging fork 16a (and hence the second axis 7) now swings (as indicated by the double-headed arrow 25), about the first axis 5. This arrangement substantially reduces variation in tension in the endless chain 8 as it passes over the sprockets 4, 6, and thus reduces the risk of chain breakage.

As shown in Figure 3, the swinging fork 16a incorporates ball-races 26 mounted on the ends of the gearbox main shaft 9a, which shaft now extends outwardly from both sides of the engine and gearbox assembly 10.

In the modification shown in Figure 4, the swinging fork 16a is located by inwardlyextending spigots 30 carried by supports 31 fixed to the sides of the engine and gearbox assembly 10. The spigots 30 have a common axis with the gearbox main axis, namely the first axis 5. This modification avoids the need for the gearbox main shaft 9 to be extended through both sides of the assembly WHAT I CLAIM IS: 1. A motorcycle comprising a frame, an engine and gearbox assembly attached to the frame in a non-pivotable manner, and an endless chain drive comprising a first sprocket rotatable about a first axis, a second sprocket rotatable about a second axis corresponding to the axis of the rear wheel, said first and second axes being disposed a fixed distance apart from each other and also disposed substantially parallel to each other, a single endless chain extending around the first and second sprockets whereby rotation of the first sprocket results in corresponding rotation of the second sprocket and thus the rear wheel, and means interconnecting the frame and the second sprocket so as to support the second sprocket in a resilient manner and whereby its axis can swing about the first axis.
2. A motorcycle as claimed in Claim 1, wherein the first sprocket is rotatable by a shaft and the motorcycle is provided with fork means supporting the second sprocket whereby its axis can swing about the first axis, said fork means being pivotally supported by said shaft.
3. A motorcycle as claimed in Claim 1, provided with fork means supporting the second sprocket whereby its axis swings about the first axis, said fork means being pivotally supported by the engine and gearbox assembly by spigot means.
4. A motorcycle substantially as hereinbefore described with reference to Figures 2 and 3 of the drawings accompanying the Provisional Specification.
5. A motorcycle substantially as hereinbefore described with reference to Figures 2 and 3 of the drawings accompanying the Provisional Specification, modified substantially as hereinbefore described with reference to Figure 4 of said drawings.