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inertia formula for con rod

I am trying to calculate all the forces (in lbf) that the connecting rod adds to the engine which influences vibration.

I am dividing the rod in between the two ends into four sections and calculating for the middle point of each as if that point had all that sections weight.

I am calculating for every 15 degrees of crank rotation.

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Here’s the formulas I have but I’m not sure about the in-line force formula:

centrifugal force in lbf = (kg x (meters/sec velocity)^2 / arc radius in meters) x .225

in-line force in lbf = (kg x (meters/sec beginning velocity^2) / 2) x .74

I am smudging a bit by ignoring the curvature of movement for calculating the in-line force but I don’t care if it’s 10% off.

I think “inertia force” is the same as what I’m calling in-line force because to stop a moving object you have to exert a force equal to its inertia. Correct me if I’m wrong.