FIELD OF INVENTION
This invention relates to a veliicle frame assembly in which the vehicle engine forms part of the vehicle frame assembly.
BACKGROUND OF INVENTION
A vehicle frame for 2 and 3 wheeler vehicles, especially motorcycles, is a load bearing structure normally fabricated in a single piece or a multiple piece construction using components such as steel tube sections, channel sections and gussets welded together in a predetermined configuration. Motorcycle parts such as the seat, side cover, engine, trailing arm, stand, footrest, fuel tank, shock absorbers, grab handles and steering assemblies are mounted or fixed on the frame at predetermined locations.
Being a load bearing structure, the frame provides the requisite strength, rigidity and stiffness to the motorcycle assembly and is designed to withstand static and dynamic loads arising out of engine vibrations, forces due to gear shifting, wheel excitation, rider weight, vehicle handling, maneuvering and so on.
There are various types of motorcycle frames manufactured according to the requirement of packaging of different parts on to the frame. Some well-known types include semi double cradle frame, double cradle frame and frame with engine as stress member, normally called a diamond frame in which the front portion of engine is mounted on a down tube of the frame or on the brackets fixed to a front member of frame.
In double cradle or semi double cradle type frames, there are two frame members branching out either from the steering tube of vehicle (which is a double cradle type) or a single frame member branching out into two at lower end (which is a semi double cradle type). These frame members form a cradle on to which the engine is mounted. In this instance, the engine rests on the cradle and does not act as a stress member.

In the case of a vehicle frame with the engine as a stress member, the engine provides the required rigidity to the frame to counter various forces and moments acting on it during various vehicle driving conditions. This type of arrangement avoids use of cradle closure of the frame below the engine for mounting the engine which reduces the weight of the frame, with inherent benefits in fuel economy and cost. Contribution of the engine to frame rigidity is dependent on the method of mounting the engine onto the frame. It depends on the width of the mounts as well as thickness of mounting brackets used, the bolt sizes and their torque specifications. The lesser is this contribution, the poorer are vehicle handling characteristics.
Therefore, it is an objective of the invention to provide a vehicle frame assembly with engine as stress member with a significantly improved torsional rigidity.
STATEMENT OF INVENTION
With these objects in view, the present invention provides a vehicle frame assembly which cooperates with an engine, the engine forming a stress member of the vehicle frame assembly; wherein the vehicle frame assembly comprises, in orientation as used in a vehicle, a front frame member connected with a plurality of frame sub members for mounting of the engine, the frame sub members extending a predetermined distance away from the front frame member.
The frame sub members, preferably two of which are provided, may be transversely spaced apart from each other, relative to a longitudinal axis of the vehicle frame assembly, while extending away from the front frame member a predetermined distance, the distance conveniently being selected with reference to packaging of the engine and its components such as silencer.
Conveniently, mounts are provided on the frame sub members for mounting one side of the engine to them. Bolt fastening represents a simple manner of mounting the engine to the frame sub members and vehicle frame without the need for a cradle mounting. The engine may be gusseted to the frame sub members

through engine mounting bracket(s), this assisting the achievement of enhanced rigidity. The other side of the engine may be connected to a rear frame member rearwardly positioned of the frame sub members, the rear frame member also being provided with mounts for mounting of the engine. The rear frame member is spaced apart sufficient distance from the front frame member and frame sub members to accommodate the engine. Both front and rear frame members may depend from an upper vehicle frame member which may be connected to a steering tube of the vehicle frame assembly. Connection or mounting of engine to rear frame member may be made in a similar manner as the first mentioned side of the engine is connected to the frame sub members. Bolt fastening is again convenient.
Preferably, the front frame member of the vehicle frame comprises a single unitary frame member connected to the steering tube of the vehicle and at the lower end of which depend the plurality of frame sub members transversely spaced apart from each other while extending downwardly to a predetermined distance.
Conveniently, the single unitary frame member connected to the steering tube may be gusseted to the upper frame member of the vehicle frame assembly. In an alternate design, each of the spaced apart frame sub members is connected to the steering tube by gussetting. A more complex gusseting means is required to provide the necessary strength between the upper frame member, the steering tube and the lower frame member.
In a further embodiment of the invention, there is provided a vehicle frame assembly comprising, in orientation as used in a vehicle;
a front frame member connected at one end to the steering tube of the vehicle frame assembly and having a plurality of frame sub members at extending downwardly away from the front frame member a predetermined distance; an upper frame member connected to the steering tube and extending towards the rear of the vehicle frame assembly;
a rear frame member connected to, and extending downwardly from, the upper frame member rearwardly of the frame sub members; and an engine mounted on said frame sub members and the rear frame member; wherein the said engine is a stress member of the vehicle frame assembly.

The vehicle frame assembly may also offer convenient packaging/routing of the exhaust system. Here, part of the engine exhaust system passes between the frame sub members.
Preferably, the exhaust system comprises an exhaust manifold which extends forward of the engine towards the front of the vehicle. The exhaust manifold then advantageously extends along the longitudinal centerline of the vehicle beneath the engine.
The vehicle frame assembly may be a frame for a two wheeler vehicle, especially a motorcycle frame.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The vehicle frame of the invention may be more fully understood from the following non-limiting description of preferred embodiments of the invention made with reference to the accompanying drawings, in which:
Figure 1 is an isometric view of a motorcycle frame with engine as a stress member according to prior art.
Figure 2 is an isometric view of the motorcycle frame in Figure 1 with engine mounted on it.
Figure 3 is isometric view of a frame of a motorcycle with engine as a stress member according to a first embodiment of the vehicle frame assembly of the invention.
Figure 4 is an isometric view of the motorcycle frame shown in Figure 3 with engine mounted on It.
According to Figures 1 and 2, the vehicle frame assembly 1 is a motorcycle frame comprising a steering tube 2, and a single front frame member or tube 3 extending downwardly provided with mounting points 4, 4 and 5, 5. An engine mounting bracket 6, provided with engine mounting points 7, 7 and 8, 8 is fixed to mounting points 4, 4 and 5, 5 of the front tube 3. The front side of engine 7a is fitted on the mounting bracket 6 through the mounting points 7, 7 and 8, 8 using suitable known hardware. The rear portion of engine 7a is fixed to a rear member 9 of the

frame 1 through the mounting bracl