Motorcycle Frame Without Cross Member for Component Space
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Solution Overview
Problem
Existing saddle riding type vehicle frame constructions either compromise on space under the fuel tank due to cross members or increase weight and complexity by omitting them, making it difficult to arrange components effectively without reducing fuel tank volume.
Innovation Solution
A vehicle body frame design without a cross member between the main frames, featuring an engine-suspending bracket that extends downward from the main frames, allowing the engine to be suspended separately and creating space for component arrangement without reducing the fuel tank's volume, while improving transverse rigidity with subframes and a resin head cover for weight savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cross member is disposed between the upper parts of the two main frames to improve transverse rigidity, then the rigidity is improved, but the space under the fuel tank is divided and narrowed, making it difficult to arrange components
Solution Approach 1:
The patent relocates the transverse reinforcement function from the upper region (cross member between main frames) to the lower region (down frame connected to head tube). This dimensional relocation allows the upper space under the fuel tank to remain open and usable, while the down frame provides the necessary transverse rigidity support at a different vertical level.
2Volume of moving object
If a frame construction without a cross member is used to increase space under the fuel tank, then the space is increased, but the frame construction becomes complicated and weight increases due to upper and lower main frames
Solution Approach 1:
The down frame serves multiple functions: it connects to the head tube, provides transverse reinforcement similar to a cross member, and creates the necessary space under the fuel tank by extending downward. This multi-functional design eliminates the need for separate cross members and complex upper-lower main frame constructions.
3Volume of moving object
If the lower surface of the fuel tank is convexed upward to secure space between the fuel tank and engine, then space is secured for component arrangement, but the volume of the fuel tank is decreased
Solution Approach 1:
The patent segments the space utilization by creating a down frame that extends downward from the head tube, separating the fuel tank mounting area from the engine area. This allows the fuel tank to maintain its full volume with a flat lower surface, while components are arranged in the space created by the down frame's downward extension.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A vehicle body frame (2) including a head tube (3), a pair of pipe type right and left main frames (28) connected to the head tube (3), a down frame (33) connected to the head tube (3) and disposed below the main frames (28), and an engine-suspending bracket (48) extending downward from the pair of main frames (28).