Geometry of Pivot

Figure 1 is explaining the calculation for placement of the pivot.This calculation ensures that the spring is at a neutral position at rotation stages of the blade. Bill Vinnings calculations work like this; distances A, B and C should all be the same measurement from the pivot hole to ensure that spring in a neutral position at the different stages of rotation. Distance A should be 10% longer than distances B and C to ensure than the spine of the blade doesn’t extend past the spring in the fully opened position. After many hours of trying to draw designs and work out the mechanism on paper, I came across printed out templates on the internet. It dawned upon me to use Rhinoceros the CAD program to draw up designs, and work out the technical confusions!