|
Anyways back to your original question, what are the benefits. Newton's 3rd law says there's a reaction force to whatever force is going through the rod, and the rod ends are free bearings so there is no torque along the rod, thus the sideloading force is determined by the rod angle and the piston's net force (it's the tangent of the angle times the net piston force). Since the tangent is increasing along the relevant interval, the sideloading force at any crank position besides 0 and 180 is greater because the rod angle is greater.
The other thing would be that since the piston is travelling slower at TDC, the pressure increase wrt crank angle is greater, and you have a higher peak cylinder pressure. As the engine speed increases, the charge has less and less time to burn. I suspect this is the main reason for going with a longer rod, as a minor change in rod ratio doesn't actually change peak forces that much.
Anyways, lower friction is good, higher peak pressure is good.
|