May 2011 • MAINTENANCE TECHNOLOGY

Cardan Shaft Alignment: These applications aren’t as straightforward as others. Their special considerations call for special tools and approaches.

A Cardan shaft is, in the simplest terms, a spacer shaft with a universal joint coupling on each end. (Its name comes from a 16th-century Italian mathematician, Girolamo Cardano.) This type of arrangement allows power to be transferred between two machines that are offset from each other.
Widely used in industry, Cardan shafts have proven practical in applications where space is limited—as well as in situations where an element in the machine train (e.g. paper roll) may need to be actuated (dynamically positioned) to an alternate position when the machines are not running. The universal joint allows for limited movement without uncoupling. To ensure sufficient lubrication circulation, which in turn prevents the universal joints from seizing, Cardan shafts are normally installed with an angle from 4 to 6 degrees at the universal joints. Experience, though, has shown that the angle between the shafts of the driver and driven unit should be kept to a minimum, preferably less than 4.36 mrads (0.25 degrees). Ideally, the angles between the driver and driven shafts and the Cardan shaft, shown as ?₁ and ?₂ in Fig. 1, would be equal. Geometrically, this would equate to zero angularity existing between the driver and driven unit: In other words, the shafts of the driver and the driven machine would be parallel to each other.

Read the entire article Cardan Shaft Alignment featuring the ROTALIGN ULTRA laser alignment tool suited for cardan-shaft applications.