Rods are constantly in either tension or compression and the forces are a straight line between the center of the wrist pin bore and the journal end bore. There are very few side to side or back and forth forces.
Are you certain? Because it is a fact the bottom of the rod moves every revolution L to R the entire distance of the stroke, granted the mass its moving is only part of the rod with the bearing, but it is the big end. In a NA motor, the only additional forces on the piston beyond inertia forces, are on an intake stroke is less then the atmospheric pressure, on compression its CR related additional forces on piston, on power stroke its cyl pressure, on exhaust its residue cyl pressure and pumping losses. Seems like there are some additional inertia forces when rod moves L to R. Has this been calculated definitively enough to be dismissed?
Bottom line, if something moves, and it has mass, there are forces involved.
