Throw Stiffness The stiffness of a crankshaft cannot be calculated exactly due to its throws. The masses are assumed to act in the middle of the crank throw. The pins and journals twist and the webs bend. An equivalent shaft is found which has the same torsional stiffness as the crankthrow. This problem was analyzed by R.GRAMMEL in 1933 and he made the following distinctions: Em xin cảm ơn!