ugggghhh! you want to get into geometry and trigonometry? this will involve sines,cosines, and trigonometry?... triangles:sides, hypotenuses, angles, Pythagorus Thereom, yuck!....you sure you want to get into this? I feel a headache coming on already...where's my advil bottle?

Here's a diagram of 2 engines with the same stroke. The top one has a long rod and high rod ratio. The bottom one has a short rod and low rod ratio.

Let's just look at one engine for now...let's pick the top one just randomly: Imagine the circle to the left is the piston. To the right is the crankshaft (square) with the rod big end attached or anchored to the crank.

Back to the circle on the left.We know that a piston travels up and down but the motion of the piston pin where the rod attaches to the piston travels in a circle described by a radius, small letter r, when the piston goes up and down.

A + C is the stroke. A + C+ D is the rod length. In the low rod ratio engine, A+B is the rod length and one side of your "triangle". What is little c?

To calculate the tangential force pressing on the cylinder wall, you need to use triangle trigonometry to solve for little r's length. The rod to crank angle is on the right side in the square, inside the triangle. We know the rod length and stroke of an engine. You can obtain the crank angle by using Pythagorus to calculate the sides of the triangle (knowing the stroke and the rod length as the sides) and then use sine or cosine.

Now, to calculate sideload force in a low vs high rod ratio motor: The tangential force of a rotating object (circular motion or our piston travelling an arc of a circle) requires that you calculate the centripetal acceleration using the radius of the circle (little r which is 1/2 the stroke) times the mass of the piston.

If you plug in the numbers into the math, you will eventually solve for the lateral force created for each engine. This is how they calculated that a longer rod has less sideload.

Use the B18B dimensions for the low rod ratio engine and the B16A dimensions for the high rod ratio engine. You can find the largest crank angle at the point where the piston is maximally loading the wall and you can also calculate that force.

I'm not going to do it since I'm too lazy right now.....

You guys still taking trig and physics in high school, go for it....

let me know what you get....I'll be back later with the cosine and sine equations used to solve for crank angle...