Weight and Friction in Theatre Rigging: How Pulleys Conquer Both

Theatre rigging professionals are faced with a paradox. Unlike most rigging applications, theatre rigging—by its very design—often calls for unprotected actors to walk around in the area beneath thousands of pounds of enormous flown hardware, electronics, and scenic elements.  

At the same time, technicians may be required to fly elements in and out quite rapidly during scene changes, so as not to interrupt the audience’s immersion in the performance. It’s no mystery that intense loads, rapid motion, and friction can combine into a recipe for danger.

How can theatre rigging equipment face (and conquer) this paradox?

Synthetic Ropes & Two-Stage Pulleys in Theatre Rigging

Modern synthetic fiber ropes and hybrid standard bearing/ball bearing pulleys each incorporate several critical features for overcoming these challenges.  In the case of synthetic fibers like high modulus polyethylene (HMPE), which can be 15 times stronger than steel cable, the advantages are obvious.  

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Dyneema® SK78

The HMPE fibers in Dyneema® SK78 rope, for example, have:

  • Enhanced abrasion resistance
  • Low elongation/elasticity
  • Minimal creep over time, even under heavy loads
  • Excellent dynamic fatigue
  • Fifteen times the tenacity of steel (pound-for-pound)
  • Higher tensile strength than steel cable at an equal diameter
  • Only 15% the weight of steel
  • A critical temperature of 150℉ (where fibers start to degrade) and a melting point of 297℉

These traits make it ideal for use high up in the flyspace, where it must support incredible loads with minimal visibility and maximum urgency. Strong synthetic ropes have advanced far beyond what was capable in old hemp systems and can now outperform steel as well.  They’re lightweight, which is integral to managing the overall load in a theatrical rigging system, and the low elasticity and creep mean that you can count on your measurements (no bungee-cording or stretch during accelerated drops). And of course, the world-class strength provides peace of mind.

Ronstan offers both Ocean 3000 and Ocean 5000 Dyneema® ropes in a variety of diameters.  But what good is strong rope without hardware that stands up to the same challenges? 

Ronstan Core Block™ Two-Stage Pulleys

A dual-bearing system helps a theatrical rigging pulley to manage competing priorities—low friction and high load tolerance.

When theatre rigging is expected to move rapidly, as is the case with abrupt reveals behind quick-flying curtains, friction is a natural byproduct. On the other hand, ponderous electrics loaded with smart fixtures, motors, winches, audio systems, and other heavy equipment can put incredible stress even on slow-moving battens that only descend to the stage for maintenance and adjustments.

The Ronstan Core Block™ is designed with two stages in a dual-bearing pulley block that is equipped to handles both situations:

  1. TIDP028-Ahe first stage relies on twin rings of self-lubricating, high-tenacity acetal ball bearings that support each side of the sheave. Under light and moderate loads, these ball bearings support the system with minimum friction.
  2. The second stage takes over under heavy loads.  As the weight increases, the compression force on the ball bearings naturally shifts them into a thrust role (protecting from axial loads). A sliding acetal bushing on a stainless steel race takes over, maintaining low friction performance with the stability of a heavy-duty bushing block.

This carefully tuned two-stage system provides excellent performance across the full working load range, with features that cater to both dynamic and high static loads. For the needs of a theatre rigging professional, this is the perfect match.

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Ronstan’s end-to-end design, manufacture and distribution operation delivers high specification products for all serious hardware applications.

Our state-of-the-art design facilities and manufacturing plant handles more than 4.9 million units each year.

As one of the top three sailboat hardware brands globally we know what it is like to deliver great equipment that can handle challenging conditions.