Abstract This paper describes the dynamic loads sustained by power chain when running at high speeds. Conditions for least destructive fatigue loading are set forth, and a formula for optimum chain speed is derived. Dynamic load tests on silent chain are reported in which the loading was measured by means of a special strain gage of the author’s design. The tests prove the loading postulated in the first part of the paper, and the conclusions indicate a new approach to chain-drive layouts for power transmission.