I needed to make some coils for a project in which the coil would serve as a hinge eye. The barrel stock would be 3/8” round and the coil stock 1/2” round. So, I needed to calculate how much stock I needed to allow for three wraps. It’s not that I distrust math and this is rather elementary but I wanted to see how close this worked out in actual practice knowing “There’s many a slip twixt the cup and the lip.”
A 30” piece of 1/2” round stock was marked with a presto pen at the appropriate transitions and I put a center punch in the fly press and laid the round bar in a “v” block and punched a mark at each designated point. Using the torch to heat the bar I carefully pulled it snugly around a 3/8” mandrel for three complete revolutions in one segment and two revolutions in another. Then I inspected the punch marks. They proved the predicted and observed results were identical.
In another project I will wrap a 5/8” round tapered element around two pieces of 5/8” square. The match between prediction and observation will be less exact because there are more technical difficulties as well as more complicated math, but I’m confident I can get close enough.
Ronald Reagan was fond of using “trust, but verify”. It is a translation of a Russian proverb which, allegedly, was also often used by Lenin. This exercise is a way of demonstrating how taking a skeptical approach and working through it can build confidence.