Originally Posted by
Peterpan1
As far as I know, with my degree in not-an-engineering, ovalizing a round stay increases it's stiffness in direct proportion to the increase in width perpendicular to the load . A racetrack oval or squarish section will add a lot to stiffness, around 60%. But whatever can be done in Ti can be done in Steel, so
I think you are right on. Making the stay ovalized makes it stiffer in one direction (against the major axis) and less stiff in the other direction (against the minor axis) as compared to a round tube. If there was room for the stay to be ovalized with the major axis being horizontal than there would be much to gain but since this is the direction where we are very limited in room its not really feasible.
You are also correct that the profile and shape of the oval would have a large effect. In fact if the stay was rectangular or square you could get more lateral stiffness from it in a given amount of room. The issue here is one of failure. With a round or even oval stay you can flex it a good long ways without issue but with a tube with flat sides (or squarish oval if you will) you put a tremendous load on those flat sides and they become very prone to beer-canning/buckling. To alleviate this one needs to make the tube walls very tick and any weight savings one gains from the material is long gone. This is why we so seldom see tubes other than round or oval in a bike.
Time for bed here. Lots of fresh snow to play in in the morning.
Dave