Solving Problems and Making Ideas come to Life
Analysis:
Based upon analysis and design of the pegs, the maximum force that the pegs will see in the neutral or stationary position is the 185 pounds of rider weight. With this force acting downwards at one end of the peg, the resulting moment force occurring at the fixed of the pegs is 50.1 foot pounds. Using the load of the rider’s weight, the amount of deflection that would occur at the point the load is applied could be calculated. Since material selection is something that is critical for this design, five differing materials were chosen to analyze the deflection amounts. These materials included Aluminum 6061 T6, Aluminum 2024, 1020 Steel, Titanium Tl-5AI, and Aluminum 4032 T6. The deflections calculated were all way less than what the required limit of half an inch. Of the five materials analyzed, the three aluminum compositions each had the most deflection at 0.004 inches. Knowing the forces and deflections acting on the neutral position of the pegs, those components could be calculated when the peg was fully rotated to the fifteen degree angle. Since the peg geometry is symmetrical, only for one side of rotation will need to be calculated as is will be similar for the other degree of rotation. The forces calculated acting upon the peg when rotated were 179 pounds in the y-direction and 48 pounds in the x-direction. These values make absolute sense as the load of 185 pounds is acting at an angle of fifteen degrees towards the coordinate plane. Solving for the moment force acting in this rotational articulation, it was found to have a moment force of 61.3 foot pounds. This value compared to the neutral value moment force makes sense as there is more force applied in this configuration of the model. Using the resultant forces found, the deflection calculations for the same five materials could be completed. Again the aluminum alloys of 6061 and 2024 had the highest deflections with values of 0.005 inches of deflection. Again these values are way below the half inch requirement which can create the assumption that deflection is not a necessary issue that will have to be troubled about during the rest of the design and testing. Calculations of various design changes such as change in peg width and height were also performed. The deflection amount with a wider and taller peg decreased, but not by enough of a significant amount to justify a change in parameters. Full detailed calculations for these numbers can be found in Appendix A. On the pivoting mechanism, there is a concern of torsion acting upon the main shaft extruding from the main body. Knowing the angle of rotation to be fifteen degrees and the length of the main shaft design from the Solidworks model, torsion could be calculated. The calculated maximum torsion that will act upon this shaft as it is accelerated towards the frontward or backwards position is 19.2 kips of force. Knowing these values of forces acting upon different aspects of the design, material can be selected for these main parts based upon density, ultimate and yield strength, machinability, and cost. For the pivot mechanism, the material was chosen to be 1020 steel do having high ultimate and yield strength values that will exceed the aspects of this design along with having a high machinability rate of 70%. Even though the steel is denser than an aluminum substitute that could have been chosen, do to design of needed the shafts to be welded into the main pivot mechanism body, steel was the better option as it is easier to weld steel than it is aluminum. Using online metals to gather pricing on the steel, it was not that much more expense than an aluminum block in the same size. The pegs material was chosen to be aluminum 2024 due to its high ultimate and yield strength compared to the other materials as well as its high level of machinability with a value of 70%. The density compared to the other materials was second to the aluminum 6061 alloy but only by twenty five thousandths of a pound per cubic inch. Even though the aluminum 6061 will cost about three times cheaper than the aluminum 2024, the 2024 composition has a greater ultimate strength with 60.2 ksi compared to 45.0 ksi for the 6061. Machinability of the 2024 is better than the 6061 by twenty percent which is huge since the peg will be machined completely using CNC milling machines.