Abstract
The transmission error in a synchronous belt was investigated experimentally in the case where the belt was generated the string vibration by resonance under the dynamics condition and the pulley speed ratio was 1:1. The period of the transmission error is 2 times per pitch. The tendency of occurrence can be estimated from the difference between the amplitudes of the string vibration due to the resonance. The transmission error in the belt greatly occurs in the first mode resonance of the string vibration.