Our project is a 4-stroke internal combustion engine that uses a slider-crank four-bar linkage formed from its piston, connecting rod, and crankshaft which transfers translational motion into rotary motion from a hand crank. Currently, an automated input for the crank is being work on; the mechanics for this will be discussed later. To create a complex motion/mechanism, we are taking the input rotation from the hand crank and are going to drive a camshaft with a belt drive. The camshaft will be designed to time the opening of the values at a appropriate time during the stroke of the piston to mimic the air flow in and the air flow out of the piston cylinder. Furthermore, for additional complex motion, there will be another pair of cams to showcase the offset valve timing and how variable cam timing works in vehicles. Below, we explain the motion and movement constraints of the slider-crank along with the attributed engine components.
The figure above showcases a slider-crank mechanism. Body 1, the gray portion, represents the engine block that remains fixed. Body 2 represents the crankshaft, body 3 the connecting rod and body 4 the piston. Describing the components further, point O2 is the crankshaft axis and main bearing with point A being the crankpin and rod bearing. The distance between the two points, O2A, represents half of the engine stroke movement. Point B is the wristpin and wristpin bearing that fixes on the piston. Distance AB is the rod length and does not affect engine stroke length, however by grash-off conditions it must be long enough so that the crankshaft can make a full rotation. Now that we have discussed the basic motions of our project, we move on to look at an in-depth kinematic analysis in the next section.