Tension and compression of a straight rods

Below is a picture of the fundamental parts of an engine. Surface "L" is where combustion occurs, air enters through "M", and "H" is the shaft through which power is accumulated and delivered out of the engine. The combustion occurs against the top surface of the piston (F) and pushes the connecting rod (G) downward, causing the shaft to move in a circular motion. So, it is easy to see that the connecting rod harnesses all of the power produced in combustion and converts it into something useful, in this case a spinning shaft.

Below is a picture of the fundamental parts of an engine. Surface "L" is where combustion occurs, air enters through "M", and "H" is the shaft through which power is accumulated and delivered out of the engine. The combustion occurs against the top surface of the piston (F) and pushes the connecting rod (G) downward, causing the shaft to move in a circular motion. So, it is easy to see that the connecting rod harnesses all of the power produced in combustion and converts it into something useful, in this case a spinning shaft.

ASSUMPTIONS AND FREE-BODY DIAGRAMS

• Now that we are all on the same page, the assumptions for this project can be discussed. First of all, it is necessary to point out that the actual dynamics of such a system are tremendous, and to model all of them in one project would be quite a task. So, to simplify, this project will neglect momentum and gravity. Only one connecting rod-piston assembly will be considered. The crankshaft, while in actuality having a very functional mass distribution, will be considered simply a circle (or if it is easier to visualize, a flywheel). In effect, many of the same calculations could be performed on a more sophisticated system, but this will suffice for the time being.

From an understanding of statics, we can represent the connecting rod of length "l" by a two-force member (this requires a few more assumptions, but for purposes of this project, it is acceptable). Given this, we can split this system into two free-body diagrams: