GB2294434A

GB2294434A - Lockable rear suspension for grass track motorcycle

Info

Publication number: GB2294434A
Application number: GB9421532A
Authority: GB
Inventors: Dennis Frederick Barber
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-10-26
Filing date: 1994-10-26
Publication date: 1996-05-01
Anticipated expiration: 2014-10-26
Also published as: GB9421532D0; GB2294434B

Abstract

A racing motorcycle has a swinging arm rear suspension 10, pivoted at 16, and provided with a device 20 for locking the suspension 14 against operation (compression) when accelerating in first gear at the start of a race. Release means 22 allows the locking device to withdraw later; for example, when the rider changes into second gear. Device 20 may be mounted to frame 18, and may be mechanically, electrically, pneumatically, or preferably fluid operated, e.g. by water, which may be dumped on the ground after use. The hydraulic cylinder may be double acting, for powered withdrawal. A manual switch may be provided, rather than being gearchange actuated. <IMAGE>

Description

Improvements relating to Racing Motorcycles This invention relates to a racing motorcycle.

Motorcycles intended for racing, especially on grass, and sometimes known as long track motorcycles, have a simple rear wheel suspension constituted by a spring loaded swinging arm on which the rear wheel is mounted. In practice, the so-called swinging arm may take the form of a simple triangular or other frame, but it is nevertheless referred to herein as a swinging arm, as is conventional in the art. The swinging arm is loaded by a spring (or springs) under compression, which extend to the maximum possible extent limited by a stop when the motorcycle is lifted onto its stand (rear wheel off the ground).

Sometimes this type of racing motorcycle also has a simple two gear gearbox, the first gear being used only for starting. Usually, it is not even possible to-revert to first gear while driving, once second gear has been engaged.

According to the invention, there is provided, in a racing motorcycle having a swinging arm rear wheel suspension, locking means for locking the suspension against operation when starting, and release means for releasing the locking means after starting.

The invention remedies a deficiency of long track motorcycles as compared, for example, to speedway motorcycles, which do not possess any suspension means. When a conventional long track motorcycle race starts, time is lost while the rear suspension constituted by the spring loaded swinging arm adapts to a condition appropriate to the weight of the seated rider.

The invention provides for locking of the swinging arm suspension on starting, in order to avoid this loss of time. After starting the locking means is releasable, because if not the rigid frame of the motorcycle would be broken or severely damaged.

It may be convenient, therefore, if the suspension locking means is automatically released when the rider switches to second gear, which in practice occurs substantially as soon as the motorcycle is moving without excess wheel spinning. Alternatively, however, separately operable releasing means may be provided.

The locking means may be of mechanical, electrical, pneumatic or hydraulic form, preferably the last-mentioned.

In an embodiment, for example, the locking means comprises a simple hydraulic ram or pump mounted on the main frame of the motorcycle and extensible to engage the swinging arm and lock said arm in the position in which the suspension loading spring is extended to its maximum to locate the swinging arm against a stop. This in effect means that the hydraulic locking means is set prior to the start of a race, while the motorcycle is resting on its stand.

It is preferred that the hydraulic locking means is not physically connected to the swinging arm, but when operated is extended into abutting engagement with the arm in order to lock the latter in position. This means that, when subsequently released when the motorcycle is being driven, the locking means is readily pushed back towards its nonextended condition by the movements of the suspended swinging arm, to remain in such non-extended condition and not be subject to unnecessary oscillations in accordance with movements of the suspension.

An embodiment of long track motorcycle equipped with the suspension locking means of the present invention is now described by way of example with reference to the accompanying drawing, the single figure of which shows the rear part of the motorcycle in diagrammatic manner.

Referring to the drawing, the illustrated motorcycle has a pivotally mounted triangular frame 10 which forms part of a swinging arm suspension for the rear wheel 12. The swinging arm 10 is loaded by a compression spring 14, so that the arm, and thus the wheel 12, is urged downwardly about the pivot axis 16. When the rider is seated on the motorcycle, in effect the rear wheel 12 is urged upwardly about the pivot 16, further compressing the spring 14. Other movements of the swinging arm 10 take place as the rear wheel passes over bumpy and rutted ground. If the rear wheel suspension was not present, the main frame 18 of the motorcycle would be damaged or broken during passage over the rough ground.

However, as a result of the presence of the spring loaded rear wheel suspension, time is lost at the beginning of grass track, long track or cross-country races due to settling of the suspension before power is transmitted to the rear wheel to start propulsion of the motorcycle.

This is one of the reasons that racing motorcycles for use on smooth speedway tracks are normally not provided with such a suspension. However, if the present invention is also employed, speedway motorcycles could be equipped with a rear wheel suspension means.

In accordance with the invention, in a long track motorcycle, a suspension locking means is provided in the form of a hydraulic pump or cylinder 20 which acts between the main frame 18 on which the device is fixedly mounted and the swinging arm 10.

When the motorcycle is resting on its stand prior to a race, the hydraulic cylinder 20 is pressurised, as with water for example, fully to extend its piston rod so that the rod comes into abutting engagement with the swinging arm 10, and thereby locks the suspension with the rear wheel 12 in its most downward position, determined by a not shown stop.

A relief valve 22 is provided on the cylinder 20, for activation by the driver, via a cable connection 24 or other suitable means, after the motorcycle is in motion at the start of a race. Most preferably, although not essential, the cable connection extends to a part of the gear change mechanism, so that the relief valve 22 is opened when the driver changes up from first to second gear. If the hydraulic fluid employed is water, this may be discharged from the cylinder 20 on to the ground when the valve 22 is opened by the release means.

The suspension is thus enabled to act in a normal manner, once starting has been accomplished at the beginning of a race. The piston of the hydraulic cylinder will be pushed back and then remain in its retracted position as a result of the movements of the suspension which take place. There is no requirement to use the locking means again until the start of another race.

In a modification, the hydraulic fluid can be transferred from end to end of the cylinder, enabling spillage on the ground to be avoided. In this case, the act of resetting the motorcycle into first gear, which normally does not take place until the start of another race, may reset the locking device into its locking condition.

Claims

1. A racing motorcycle having a swinging arm rear wheel suspension, having locking means for locking the suspension against operation when starting to travel and release means for releasing the locking means after starting.

2. A racing motorcycle according to claim 1, wherein locking means is a retractable member for engaging the swinging arm to prevent its pivotal movement.

3. A racing motorcycle according to claim 1 or claim 2, wherein the locking means is hydraulically operated.

4. A racing motorcycle according to claim 3 when appendant to claim 2, wherein the hydraulic locking means comprises a hydraulic cylinder and piston extensible to engage the swinging arm.

5. A racing motorcycle according to claim 3 or claim 4, wherein the hydraulic locking means is fixedly mounted on the main frame of the motorcycle.

6. A racing motorcycle according to claim 4 or claim 5 when appendant to claim 4, wherein suspension locking is achieved by pressurising the hydraulic cylinder to extend the piston, and the release means is operable to release the pressure in the cylinder in order to enable the piston to retract.

7. A racing motorcycle according to claim 6, wherein the hydraulic f2b-id is water.

8. A racing motorcycle according to claim 7, wherein cylinder pressure is released by discharging the hydraulic fluid in the cylinder on to the ground.

9. A racing motorcycle according to claim 6, wherein the hydraulic fluid is transferred from one end of the cylinder to the other in order to extend and enable retraction of the piston.

10. A racing motorcycle according to claim 4 or any claim appendant thereto, wherein the release means comprises a pressure relief valve in the cylinder operable by a cable connector.

11. A racing motorcycle according to claim 10, wherein the cable connector is operable by a driver accessible control element.

12. A racing motorcycle according to claim 10, wherein the cable connector extends to a part of the gear change mechanism of the motorcycle, whereby to be operable automatically when the driver changes up out of first gear.

13. A racing motorcycle according to any of claims 1 to 12, being a long track motorcycle.

14. A racing motorcycle substantially as hereinbefore described with reference to the accompanying drawing.