Proposal of the formula to calculate the amount and direction of unbalance in order to achieve the desired ratio of crank shaft balance and the desired angle of principal axis of inertia

Abstract

In recent years, the number of motorcycle engines adopting cylinder offset has increased. But a formula for determining the amount and direction of unbalance added to the counterweight of the crank shaft necessary to achieve the desired ratio of crank shaft balance and the desired angle of principal axis of inertia used when adopting the cylinder offset is not shown even though that is important especially in the crank shaft design stage. As a result of verification using the actual product, it was confirmed that the amount and direction of unbalance required to achieve the desired ratio of crank shaft balance and the desired angle of principal axis of inertia are expressed by the following calculation formula.