I was wondering if any of you might be able to help me out. I am designing an AC servo-motor drive that will position tooling on a straightening press. During deflection of round axles (3" diameter - steel) with a displacement of 2" at any point along a 98" span with both ends loosely supported on a ledge on each end, the reaction forces on the bending head will attempt to push the head out of position. The position of the head must be maintained during bending. In order to figure out what these reaction forces are I need to know the deflection at the point of the bending head. With this figure I can work back and determine what force is working against me, hence I will be able to size the torque necessary to keep it in position. Bottom line, I need a formula for deflection of a beam with a round cross section. My problem is that it has been years since I have taken a look at that analysis and I have lost my text from my Mech. Eng. courses.

Engineers edge has these bending formulas but I am not sure about some of the variables they request. The formula is found on...

www.engineersedge.com/beam_bending/beam_bending3.htm

My question is, do any of you know what the X and Y variables are and how do they differ from a and b? Also, what is variable Z (which is found in the calculator)? They refer to it as The distance from neutral axis to extreme edge(fiber). I am assuming they are refering to the distance from the centerline axis of the cross sectional area, which in a round bar is half the diameter, to the outside edge where the load force will be applied by the bending head. I am just not sure if that is right.

In any event, if you guys/gals can help I sure would be appreciative.

Best regards,