Motorcycle engine mounting system

Details Motorcycle engine mounting system Motorcycle engine mounting system

2001-12-07

2003-07-08

Lerner, Avraham (Department: 3611)

Motor vehicles

Special wheel base

Having only two wheels

Reexamination Certificate

active

06588530

ABSTRACT:

FIELD OF THE INVENTION
The present invention is in the field of motorcycle chassis, and pertains more particularly to systems for mounting motorcycle engines to the chassis.
BACKGROUND OF THE INVENTION
Since the introduction of the first two-wheeled self-propelled motorcycle, which was a converted bicycle with a small, centrally mounted spark ignition engine, many design improvements and other innovations have been incorporated to improve such aspects as speed, power-to-weight ratio, and handling and stability performance. Motorcycles with engines having larger power capacity and engine displacements were increasingly desired early in development because of the increased speed and acceleration capabilities, and required innovative advancements in the technology pertaining to chassis and power train rigidity in order to handle problems caused by greatly increased stresses that could be imposed upon the components during operation of such higher performance motorcycles.
During normal operation of motorcycles the front and rear wheels rotating within the same plane are continually subjected to forces urging them from their proper alignment in order to keep the motorcycle balanced upright within the center of gravity. Even while traveling a straight line the motorcycle must be alternately steered into the direction it is leaning to keep from falling over. The resulting operating loads, although slight during traveling a straight line, are greatly increased during the execution of a turn, becoming quite extreme when the turn is executed at high speeds. Handling and stability can be greatly compromised if the motorcycle chassis does not provide a sufficient level of strength and rigidity.
Much handling and stability performance for a motorcycle is also lost if the suspension of the motorcycle allows the wheels to be excessively forced from their plane of rotation. For example, the rear wheel, rotatably attached to a rigid swing arm having usually a pair of extended arms cantilevered at the rear of the frame, a standard design in the art, is particularly exposed to such forces during high-speed turns. Any excess deflection from its vertical plane during a high-speed turn can seriously impact stability and handling causing an unsafe condition. It is also therefore important to limit, as much as possible, any movement of the rear swing arm that is in a direction other than that within its intended vertical movement.
A maximum level of handling and stability performance is only achieved when deflection as described above is minimized, to the greatest extent possible, by sufficient rigidity designed into the combined functions of the frame, drive train and suspension, so that only minimal deflection by operating loads of the wheels from their proper alignment is allowed. Many methods have been developed, well known in the art, for improving characteristics of strength and rigidity in the chassis, drive train and suspension.
The chassis of most motorcycles is a frame, usually a combination of tubes and sheets most often manufactured of steel that can be arranged in a variety of different design configurations for different styles and types of motorcycles. The frame is preferably designed to have sufficient stiffness and rigidity, particularly in areas of the frame that would endure pronounced stresses during operation of the motorcycle. One method well known in the art of motorcycle frames, and all related structural art, is the use of triangulation and cross support members in the frame design. Another well-known method of supplementing overall chassis rigidity is a method, more commonly used in the past, of incorporation of a rigid engine mounting system whereby the engine itself is rigidly mounted to the frame and becomes a partially-stressed member of the frame, supplementing the overall rigidity of the chassis. Also, more rigid and stronger connections between the engine and transmission have been used in some cases to supplement rigid or semi rigid engine mount systems, increasing the overall collective rigidity of chassis, power train and rear suspension.
Rider comfort also quickly became an item of much attention in early development, leading to the introduction of many related improvements such as, for example, shock absorbing suspension systems for both front and rear wheels, and advancements in technology pertaining to balancing of reciprocal and rotary vibration of engine components, both being methods for reducing the level of road and engine vibration ultimately absorbed by the frame and rider. The engine of any motorcycle must be designed so that the rotary and reciprocal vibration caused by the internal moving parts are balanced to reduce vibration to a level acceptable in accordance with the intended durability of the frame and engine mount system of the motorcycle, coupled with the level of comfort that should be expected by the rider.
Certain classic styles of motorcycles, such as those designed with long, lower-profile frames and large twin-cylinder engines having high displacement, power and torque, have experienced and retained wide and ever-increasing popularity in today's market. This is largely due to the powerful and nostalgic look and feel, as well as improved performance, comfort and other desirable aspects unique to the style. The cylinders of the engine in such a motorcycle are most often arranged in a vertical “V” configuration; hence the name “V twin” as is commonly used in reference. The pistons within the cylinders and many other engine components are typically much larger and heavier than those of a common smaller displacement four-cylinder engine, producing a much higher level of vibration when the engine is operated, particularly true when the engine is operating at lower or idle speeds or in a high-torque situation. Such vibration, when not sufficiently isolated, can be extremely injurious to the chassis and components, causing fatigue to the frame and problems such as early weld failure or cracks, and so on, and also can be uncomfortable to the point of unbearable to many riders. A motorcycle engine with more than one cylinder has more than one connection point between piston and crank shaft, causing reciprocal and rotary vibration, always existing to some extent regardless of the level of balancing designed into the moving parts of the engine. Different styles of engines have varying numbers, sizes and configurations of cylinders and therefore generate greatly varying levels of vibration. For example, a motorcycle having a smaller displacement four-cylinder engine with much smaller pistons has, because of its design, smaller and more numerous moving internal components, and when the engine is operating the resulting vibration is less pronounced. Conversely, a large displacement twin cylinder engine such as described earlier has large pistons causing much more pronounced vibration, and when combined with the vibration of the other typically heavier internal components, an excessive amount of vibration can be generated, particularly at idle speeds.
Although significant advancements have been made in technology pertaining to the balancing of reciprocal and rotary vibration of engine components, the basic nature of some engine designs, such as, for example, large-cylinder engines as described above, makes balancing to an acceptable level extremely difficult, at least partly due to the orientation and vertical travel directions of the large pistons within the cylinders, causing, along with other internal components, the rotary and reciprocal vibration. In conventional art manufacturers have attempted to solve the vibration problem by utilizing a variety of methods, such as elastomeric engine mounting systems using soft interfaces of various size and durometer, often manufactured of rubberized or similarly resilient material, for mounting the engine to the frame. Such resilient interfaces can sometimes have different aspects of adjustability, and in typical cases they are used in all of the engine mounting locations, usually located at both the fron

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