Motorcycle Muffler Rhombus Cross-Section Design
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Solution Overview
Problem
Existing motorcycle designs face challenges in minimizing sideway bulging of mufflers from the vehicle body while maintaining ride comfort and avoiding interference with other components like the drive chain and rear brake disc.
Innovation Solution
The design features a muffler with a rhombus cross-sectional outer shell and side covers that are inclined to minimize bulging, allowing for a lower profile and avoiding interference with other components, along with a baffling structure in the exhaust pipe system to enhance sound deadening and reduce the vehicle's width, and a rear brake caliper supported by the swing arm to increase shock absorber stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the muffler is disposed upwardly of the rear wheel to avoid interference with the drive chain or sprocket, then interference is avoided, but the sideway bulging of the vehicle body is increased and ride comfort deteriorates
Solution Approach 1:
The muffler cross-section is changed from a conventional circular or obround shape to a rhombus shape with specific diagonal orientations. The long diagonal is oriented in the vehicle width direction while the short diagonal is in the vertical direction, allowing the muffler to extend primarily in the width direction rather than the vertical direction, thus avoiding interference while minimizing bulging
Solution Approach 2:
The rhombus cross-section creates an asymmetric geometry where the side walls are inclined at specific angles. This asymmetric shape allows the muffler to be positioned lower while maintaining adequate clearance from the drive chain and sprocket, reducing sideway bulging compared to symmetric conventional shapes
2Reliability
If the crosswise width of the vehicle body is enlarged to accommodate the muffler, then interference is avoided, but the vehicle width is increased affecting ride comfort
Solution Approach 1:
The rhombus cross-section with long diagonal in the width direction allows the muffler to achieve adequate clearance from rotating components by extending in the width direction rather than requiring increased vehicle width overall. The inclined side walls direct the bulk of the muffler volume inward toward the vehicle centerline
3Shape
If the muffler is disposed lower to improve ride comfort, then ride comfort improves, but interference with the drive chain or sprocket occurs
Solution Approach 1:
The rhombus cross-section with inclined side walls creates an asymmetric profile that allows the muffler to be positioned lower while the inclined walls extend outward upward to clear the drive chain and sprocket, maintaining both low profile and interference avoidance
Data Source
AI summary
A motorcycle with a muffler disposed downwardly of a rider's seat positioned, in a side view, upwardly of a rear wheel when a rear shock absorber is extended, to minimize sideway bulging of the muffler from a vehicle body and improve ride comfort, while avoiding interference between the muffler and other parts. An outer shell of a muffler has a rhombus cross section. The muffler is disposed on at least one side in a vehicle width direction of a rear wheel wherein one pair of side walls extend in parallel with each other out of side walls of the outer shell extending in a vertical direction. A side cover is formed to extend along the upper and outer side walls of the four side walls of the outer shell to cover the muffler from a side, downwardly of a rider's seat.