Introduction by Nigel Mullion
Phil Irving MBE, (the respected engine designer) seems to have first suggested the idea and proposed that a 76° stagger was preferable. At least one motorcycle manufacturer has produced a twin cylinder engine with crank pins staggered at 90°. Some motorcycle owners have modified their engines using one or other of the angles.
This article analyses various crankpin spacings and includes a crankpin spacing that will optimise the flywheel effect of the pistons. Mathematical proof is provided. The proof also shows that the position where a piston reaches maximum velocity is dependent upon the ratio of the crank arm to conrod length. There is a practical application with a Norton motorcycle with its engine crank pins staggered at 80°.
UNDER CONSTRUCTION - TO BE COMPLETED