January 2022

38 n GEARS AND GEARBOXES January 2022 www.drivesncontrols.com Gearboxes make West End show an uplifting experience W hen the Duke of York’s theatre in London’s West End was preparing to stage a production of a National Theatre show, The Ocean at the End of the Lane , it needed several automated elevators to lift heavy props from below the floor to the stage level. A key requirement of the drive systems for these lifts is that they needed to be extremely quiet. They also had to fit into tight spaces. A further challenge was that the lift systems would need to be designed, built and installed within a 12-week lead time. Short lead times are common in the theatre industry and can pose a challenge. To speed production, motors and gearboxes are often specified before the design process is complete, leaving the supplier free to overcome design issues relating to each show’s unique requirements. It also allows them to accommodate unknown factors as they occur. If the show proves to a success, the lifts may need to continue working reliably for far longer than initially planned. For this production, four lifts of differing specifications were needed to raise and lower various props including two door frames, a bench, and a bath that weighs 850kg, at speeds of up to 300mm/s. The lifts cover vertical distances to the stage of between 450mm and 2.1m. The Duke of York’s commissioned the Surrey-based theatre specialist Absolute Motion Control to design and supply the lifts. For the gearboxes, the company chose right- angle helical-bevel gearboxes from Stober’s ServoFit K Series, which can be fitted using tapped rather than through-holes on all sides of the gearbox. This makes them easy to install them in tight spaces. Without the inconvenience of using nuts and bolts, the engineer simply screws into a tapped hole. The gearbox for the door-lifting mechanism, for example, turns a 30mm driveshaft with a chain sprocket that moves a platform carrying the prop up to the stage and then down again at the end of the scene. There is also a secondary belt-drive to a rotary limit box to protect the mechanics from over-travel. Another attraction of these gearboxes for theatre applications is that they are manufactured in black as standard. This means that they do not need to be repainted, which can cut production lead times by one or two weeks. Also, it avoids unnecessary additional costs. During performances, the lifting systems are controlled by a stage engineer from a central control position. Similar gearboxes are used in other theatres to drive rotating steel floors – a popular effect in West End productions. In these applications, the dimensions and ratios of the gearboxes are key. For example, a Stober K102 gearbox can deliver the power to rotate a 200–300mm deep floor. Its small size also means that it fits in the limited space available. Apart from the floor’s steelwork, the gearbox and the motor are often the largest components of the rotating floor. The size, weight, ratio and power output of the gearbox can have a major impact on the budget and cost-effectiveness of creating the required motion. On attraction of the Stober gearboxes for Absolute Motion Control is that they offer ratios up to 70:1 for two-stage versions, and 271:1 for three-stage models. According to one of the company’s directors, Ben Phillips, this is “something we have found impossible to match from other manufacturers”. Another attraction is the availability of online configurators to specify the gearboxes, and product datasheets that provide the specifications in an easily accessible and understandable way. For instance, the torque variations are supplied in numerous formats, so speeds, acceleration and torques are easy to relate to, taking care of the many calculations that back-stage engineers require. n A newWest End theatre production needed a series of compact, silent lifts to raise props to the stage level. A key element to achieving this was the use of helical bevel gearboxes that are easy to install in tight spaces. One if the theatre’s prop-lifting platforms being prepared for installation below the stage