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each stroller leg are 98.1N in y-axis and 100N in x-axis direction.
77 Figure 29: Height and Weight chart for boys from age of 2 to 15 years old. Fy = 98.1N Fx= 100NConnected to main body Figure 30: Reaction forces transmit from the wheel to the lower arm.After gathering all of these forces, simple lever analysis and force analysis calculations were performed to find out the resultant forces that might be acting on the selected parts which are the main steering holder and steering. The lengthy and complete manual calculation about the
78 reaction forces acting on the steering and main steering holder were attached in Appendix 7.3, Figure 48. In the calculation, we analyse the forces by assuming the absorber as a rigid rod to maximize the magnitude of force that will acting at each join to obtain higher factor of safety ( In practical manner, the reaction force at each joint might be smaller due to the spring will absorb partial of the force). Figure 30show the reaction forces and the constraints that acting on the overall suspension system design. The resultant forces acting on each selected parts, stress analysis, mass analysis and optimization of the selected parts will be discussed in the next few sub-chapters. 6.1.1Creo Parametric software analysis on steering part: 126.96.36.199Resultant forces acting on steering: The manual calculation for resultant force analysis was shown in Appendix 7.3, Figure 48. the computed resultant forces were set and applied to the steering part model that created using the Creo Parametric simulation software as shown in Figure 31 at below. The red arrow is the direction of the forces and the magnitude of the force was listed in the box; the center hole was set as fixed constraints as it is directly fit into the main steering holder rod. F2=198.19 F1x=100 N F1y=42.04 N Fixed constraints Figure 31: Schematic diagram of reaction forces that acting on the steeringpart.
79 188.8.131.52Structure strength analysis –sensitivity studies: Figure 32shows the result of software structure strength analysis. The major portion of the structure is in blue colour which sustaining very low amount of von misses stress and only the holder parts sustaining highest amount of von misses stress which is 47.37MPa and result in factor of safety of 1.16 (Ultimate yield strength for aluminium 6061 is 55MPa). Because of the tube part is consider as compact structure already due to bearing need to fix inside the it; thus, the best parameter can choose to optimize is the holder thickness (upper and lower holder) only. Figure 32: Steering structure strength analysis. Lower holder Upper holder
80 Figure 33shows the sensitivity graph of von misses versus the thickness of the upper and lower holder. Based on the graph shown, the von misses stress does not change much and stay in between 47.20MPa to 47.45MPa when the holder thickness changing in between 5.50mm to 10mm. Thus, the thickness can be choosing to reduce to minimum amount during optimization.