The designer had to combat strength with weight requirements. This is why the rod has a hollow center and is reinforced in crucial areas. Also, the designer had to include methods of lubrication. Allowing the piston to seal to the walls of the cylinder was also important so no gases can escape.
The piston/rod assembly has to be very strong. The Base of the piston is 0.12 inches thick, which is nearly twice the thickness of the wall at 0.075 inches. The crank is very thick at 0.5 inches and is reinforced around the both points of rotation (1). The smaller part of the rod is reinforced around the bolts and has ribbing to help withstand large forces (2). All these things are done to withstand the explosive forces produced during combustion. Another important feature found throughout the assembly are the inclusion of holes to allow oil to lubricate the friction points around the crankshaft and the piston sleeve (3).
The piston/rod assembly is designed to be loaded in the vertical direction from the combustion forces. This force is then transmitted via the rod to a rotational motion on the crank. This produces forces in both the X and Y component on the upper part of the rod that vary with the position of the piston itself. Along with there loads high temperatures and vibration rates are also applied to this assembly.
Methods of Performance Evaluation
We can figure out the maximum compressive loading that the piston and rod can take but doing a direct load on the piston and by performing a buckling test on the rod. We can test the retaining force on the bolts using a tensile test. The temperature effect can be tested by placing the parts in a furnace and performing the previously mention tests.
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