How are the actuation cables in multi-stage telescoping lifts tensioned?

[Robot360]

Originally Posted by jspatz1

In both our cascade-rigged telescopic lift in 2011, and our continuous-rigged telescopic lift this year (2013), we maintained tension and accommodated small variations in overall length by terminating the cable with a strong extension spring. The spring takes up variations in the rigging length as the apparatus extends and retracts, and is placed on the non-loaded side (or "down" side) of the rigging. A small loop of slack cable is also placed around and parallel to the spring as a shock cord, to create a maximum limit to how much the spring can stretch. This protects the spring in cases where the mechanism gets caught or snags, and the down direction sees a high load.

Jeff, thanks for the response and details. For your setup, could you ever get in a situation where your lift snagged, maximizing the spring stroke (that is, to its limiter), and then if you continued driving the lift, cable slack would end up in the system?

Also, how many layers of cable wraps are typically on your full drive pulley, and with what diameter cable? Even a few layers of 1/4" cable could result in several inches of cable slack.