A regular fly-bar does not have the required strength if the uniformly distributed load needs to be upgraded from 300kg to 500kg and the point load from 40kg to 150/200 kg. Therefore, the single round tube is often replaced with ladder beams, usually made from steel. ProTrac offers a better alternative than these steel ladder beams, being specially designed to meet the demands from a modern theatrical environment and the CE compliance for lifting equipment, say the company.
Prolyte says ProTrac is a combination of an aluminium extruded rectangular profile underneath which a round tube of 60mm or 48.3mm is attached. ProTrac is very flexible in use; several lengths can be easily combined and connected.
The system that is delivered to the Royal Opera House is based on the standard Pro Trac system, but uses a custom-made, high-grade aluminium extrusion to comply with the particular specifications of the theatre. The total installation comprises of 121 fly bars of 24m length, including suspension points, which is over 24 tons of aluminium! The fly bars were delivered in lengths of 12m, where they were coupled to obtain the total required length of 24m. Very narrow tolerances for torsion and straightness of the profiles was specified to be able to comply to the high demands the theatre required. The lateral stiffness of the Pro Trac must be very high, as the centre-to-centre distance of the tracks in only 150mm. This leaves no room or tolerance for any lateral (sideways) bending of the profiles. Further, the profiles were filled with PU foam, to reduce any noise caused by running trolleys on the bottom flanges of the profiles.
(Lee Baldock)
