These are some great ideas! Actually, John Child’s eccentric hub crank is something I’ve thought of before but Dave’s idea is one I’d never considered.
I got so excited about the two ideas, I decided to do a little design work. The attached .jpg file shows Dave’s idea on the top with John’s idea below - both mated to my extra wide hub.
Dave’s crank is adjustable to five positions: 170mm, 163mm, 147mm (shown), 129mm and 120mm. When made from aluminum with a short steel splined shaft between the two crank parts the weight of one cranks is 1.02 pounds. The spline pattern is the 8 spline KH.
John’s crank is adjustable to six positions: 170mm, 165mm, 156mm, 142mm, 130mm and 125mm. With the eccentric hub and crank made from aluminum (and the lightening holes as shown) one crank weighs 1.11 pounds. By contrast a 170mm Profile crank weighs about .64 pounds.
I think cyberbellum is right on about the splined joints being something with no slop. A pinch type arrangement should work pretty well in both designs.
I know what the next question is: When am I going to make a set?
Steve Howard
