Rising star of theatre land

A leading UK manufacturer of automated equipment for theatre productions has specified STOBER gearboxes for the delivery and retraction of stage props in a West End show. In fact, gearboxes supplied by motion control experts STOBER Drives are regularly specified by theatre supplier Absolute Motion Control for their control systems that move props and scenery during performances.

‘The Ocean at the End of the Lane’, a National Theatre show running at the Duke of York’s theatre In London’s West End, needed automated lifts that incorporate servo motors, gearboxes and drives to elevate door frames, a bath and benches etc, from below the floor to the stage.

The nature of the theatre industry itself posed the key challenge of finding extremely quiet servo drive systems with typical requirements that would fit into tightly confined spaces.

12-week lead time

A further challenge was to create these within a 12-week lead time. Short lead times are common and are a particular challenge in the theatre business. To speed production, the motor and the gearbox are often specified before the design process is complete, which leaves the manufacturer free to overcome specific design issues relating to each show’s unique requirements. It also allows them to accommodate unknown factors as they occur.

Then, subject to the success of the show, the props may need to continue to work faultlessly for far longer than the initial run.

For this show, four lifts of differing specifications were required to raise and lower two door frames, a bench and a bath that is 850Kg at 300mm/sec. The lifts cover vertical distances to the stage of between 450mm to 2,100mm for the various props.

Tapping into the action

Absolute Motion Control selected from the K Series of right-angle helical bevel ServoFit gearboxes, which can be fitted using tapped, rather than through, holes on all sides of the gearbox. This makes it very easy to install them in tight spaces and without the inconvenience of a nut and bolt; the engineer simply screws into a tapped hole.

On the door lifting mechanism, for instance, the gearbox turns a 30mm driveshaft with a chain sprocket that moves the platform, upon which the prop is mounted, up to the stage and down again at the end of the scene. There is also a secondary belt-drive to a Rotary Limit Box that is designed to protect the mechanics from over-travel. During performances, the lifting systems are each controlled from a central control position by a stage engineer.

Typically, other show sets use these gearboxes to drive rotating steel floors, which currently is a very popular effect in the West End. In these applications, the dimensions and ratio of the gearboxes are key. For example, the automation mechanics are built to turn a 200mm to 300mm deep floor, and a STOBER K102 gearbox will deliver the power needed to do this. Its small size also means that it fits within the parameters of the floor, which are always tight.

Huge impact

Apart from the steelwork, the gearbox and the motor are often the largest aspects of the floor and, on a 200mm or 300mm thickness floor, the size, weight, ratio and power output of the gearbox has a huge impact on the budget and cost efficiency of creating the required motion.

Another simple but important factor is that STOBER gearboxes are manufactured as standard in black, something that is of high importance in the theatre industry. This means that the gearboxes do not need to be repainted, which can reduce the production lead time by one or two weeks. Also, it saves unnecessary additional costs.

“So many factors are taken into account in our partnership with STOBER,” says Ben Phillips, of Absolute Motion Control. “As well as the colour, we have found that the ratio of STOBER K series goes up to 70:1 (2 stage) and 271:1 (3 stage), something we have found impossible to match from other manufacturers. Another important factor is the personal contact we enjoy from them, which gives a reliable and personal feel to their service. This makes STOBER much more user-friendly to theatre industry requirements.”

Full specifications

Another big benefit are online configurators to create solutions, and individual product datasheets that provide all the specifications the engineer needs 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, which means that the many calculations an engineer in the show’s back-stage team requires are taken care of.