Originally Posted by
repechage
might be wrong, but some club manufacturers have the shaft drawn with the wall thickness varying? The OD being a circle, and the ID an oval? Or, not a constant wall thickness anyway.
one tube supplier played with wall thicknesses is an about way, I forget who, and did not catch on obviously.
In golf shafts a number of designs have been tried including a seven sided mandrel for the interior of the tube that is then drawn into a round shaft, and even stiffeners added to the inside walls of the shat to stiffen it in carbon fiber shafts. But the Rules of Golf prohibit these products due to the rule that states the shaft should not have unequal bending properties in any plane of the 360* of rotation.
However in mass produced steel tubes it is impossible to have those properties. Each shaft/tube will have a bending plane that is more flexible by a few thousandst of an inch hence the interest in spring constants for me. But it also asks me to wonder if the flexing of bike tubes in similar ways and how when assembled if those flexibility planes in shafts can affect the performance of a frame. Perhaps just a bit of speculation on my part but something that I'm sure bigger minds than mine have investigated in bicycle design. Smiles, MH