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

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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.