LEVER OPTIMIZATION FOR TORQUE STANDARD MACHINES

摘要

The lever arm length, i.e. the distance between the force-acting line and the rotation axis of the lever, directly defines the torque that is acting in a torque measuring machine of the lever type. Therefore, already in the design process of the 20 kN·m static torque standard machine finite element calculations had been carried out at PTB to optimize the lever geometry in order to guarantee the constancy (within the limits of the uncertainty of measurement of the machine) of the lever arm length, even during loading. The absolute measurement of the lever arm length had still been a problem at this time. The present work describes the method of defining the lever arm length using a calibrated precision end gauge. With this gauge the above mentioned constancy of the length during the loading procedure can also be proved. Furthermore, the chosen lever geometry has an additional advantage ― it permits the very sensitive adjustment of the lever arm length in the μm-range, when the bent side plates are tightened against each other. The measurement results demonstrate the success of this procedure.