Question: How can I calculate the required surface area of rubber that a given force acts on to cause a pre-determined deflection in the rubber bushings described below?
I have modified a motorcycle frame wherein I isolated the drive train from the frame in an attempt to isolate engine vibration for the rider. The drive train (engine/transmission/rear wheel) is mounted in the frame (front wheel/frame/seat/etc.) with a 2" x 4" rubber mount at the front, and two cylindrical polyurethane bushings where the rear suspension normally (rigidly) mounts to the frame. The rear polyurethane bushings have failed in the direction of the fully extended position for the rear suspension springs. The failure has occured because the spring restoring force (spring constant) associated with the suspension is too great in magnitude for the polyurethane bushings I used. I would like to spread the load out over a larger area of rubber (polyurethane has too high a durometer value) in order to lower the deflection, and thought I could do so knowing only the spring constant (force) and durometer rating of the rubber I would use. I was going to take the zero A scale deflection (2.5mm) and the area of the durometer gauge (approximately .39mm diameter) to arrive at value of deflection/in^2 surface area for a given force applied. Any ideas?
I have modified a motorcycle frame wherein I isolated the drive train from the frame in an attempt to isolate engine vibration for the rider. The drive train (engine/transmission/rear wheel) is mounted in the frame (front wheel/frame/seat/etc.) with a 2" x 4" rubber mount at the front, and two cylindrical polyurethane bushings where the rear suspension normally (rigidly) mounts to the frame. The rear polyurethane bushings have failed in the direction of the fully extended position for the rear suspension springs. The failure has occured because the spring restoring force (spring constant) associated with the suspension is too great in magnitude for the polyurethane bushings I used. I would like to spread the load out over a larger area of rubber (polyurethane has too high a durometer value) in order to lower the deflection, and thought I could do so knowing only the spring constant (force) and durometer rating of the rubber I would use. I was going to take the zero A scale deflection (2.5mm) and the area of the durometer gauge (approximately .39mm diameter) to arrive at value of deflection/in^2 surface area for a given force applied. Any ideas?
