DoppelKardanen

DoppelKardanen, or double Cardan joints, are a drive-train configuration used to transmit torque between two shafts that are not perfectly aligned. The arrangement places two universal joints in series, separated by an intermediate shaft, so that the first joint couples the input shaft to the middle shaft and the second joint couples the middle shaft to the output shaft.

The two Cardan joints can cancel the non-uniform angular velocity produced by a single joint if certain conditions are met: the operating angles of the two joints are equal, and the yokes are phased 90 degrees relative to each other. Under these conditions the instantaneous velocity fluctuations of the first joint are largely offset by the second, yielding a more constant average output speed over a range of operating angles. In practice, perfect constant velocity is not guaranteed; deviations depend on angle, manufacturing tolerances, and lubrication.

Design considerations include precise phasing of the joints, the length of the intermediate shaft to maintain proper alignment, and the ability to accommodate thermal expansion and slight misalignment. The system is simpler and cheaper than a true constant-velocity joint, but requires careful maintenance and periodic lubrication of the universal joints.

Applications are found in automotive drivetrains, industrial machinery, and older designs where a true CV joint is impractical or too costly. DoppelKardanen can reduce vibration compared to a single Cardan while offering a compact solution, albeit with some residual velocity fluctuation at larger angles or speeds.