Factors to consider when specifying brakes for theatre and stage applications

Avoiding drama in a theatre seems like an odd thing to be doing, but KEB specialises in it. The company has been supplying spring-applied brakes for the theatre and stage industry for more than 40 years. From deck winches and turntables to line shaft hoists and orchestra lifts, a range of factors should be considered when specifying brakes says KEB Automation’s Jonathan Bullick.

There are many factors to consider when specifying brakes for theatre and stage machinery such as hoists, lifting equipment and winches. These factors include safety, noise levels, hand releases, microswitches, double brakes, load brakes and double interposed brakes.

Safety

Typically for theatre and stage equipment, a power-off failsafe brake is desired, particularly if the application is a hoist lifting an overhead load. Some theatres have been known to install large permanent magnet (PM) servo motors for the hoisting axes, with the motors equipped with PM brakes. While PM brakes do provide power-off brake engagement, they are not ‘failsafe’ because if the air gap becomes too large through wear or misadjustment, the brakes can fail open and unsafely.

Electrically released spring applied brakes are more suitable, as they use multiple springs embedded in the magnet housing to provide failsafe power-off braking. For this reason, KEB offers spring-set brake designs for servo motors if needed. As drives are usually used in these applications, spring applied brakes can be rated for holding torques, typically giving 50% more torque for the same size of brake.

Noise reduction

If a theatre hoist or winch operates during a performance, the machine and all of its components should generate as little noise as possible.This is normally not a problem for small brakes, but becomes more challenging when using larger brakes. Large DC spring-set brakes have an armature that actuates back and forth, making metal-to-metal contact with the magnet housing. The noise can be significant and becomes more noticeable the larger the brake and the larger the moving armature mass.

Several design features can be employed in brakes which dampen the actuation noise. Our own theatre brakes, for example, as standard are designed to produce less than 65dB noise measured at a distance of 1 metre. In practice, these brakes are even quieter. Typically, other automation components in the machine application such as motor contactors and gearing produce more noise than our brakes do.

Hand release

A manual hand release allows the brake to be released without electrical power. This can be very useful for diagnostics and machine commissioning. For some theatre applications such as when a performer flies across the stage, a hand release is absolutely required and is not an option. In the case of a loss of power, a performer must be able to be lowered rather than hanging indefinitely in the air.

Microswitch

A microswitch provides engagement feedback of the brake state. It is always a good idea to use a microswitch to give extra peace of mind, particularly when flying performers or applications that move very large loads such as speaker clusters or orchestra pits.

A microswitch on the brake will certainly add extra cost to the brake so the requirements of the application must be taken into account. It should also be noted that some external control is needed to evaluate the microswitch signal. This typically takes the form of a VFD or PLC. Our own microswitches can be configured for either NO or NC configurations.

Double brake

Redundant braking is often preferred or required in theatre and stage machines. There are a number of different ways to achieve this and the geography of the installation often dictates the brake placement and machine design.

For applications that require two brakes on the high speed motor side, KEB’s D8 spring-set brake can be used. The D8 double brake is basically two brakes with independent electrical and magnetic circuits. Each brake is controlled and powered separately and is capable of stopping and holding the rated load by itself. The D8 design is very compact and the brakes ship from the factory with pre-set air gaps so the installation is straightforward. Options such as hand releases and microswitches can still be implemented.

Load brakes

One alternative to using a double brake on the motor side would be to place one brake on the output (gearbox) side of the machine in addition to the gearmotor brake. This output brake is typically referred to as a load brake or parking brake.

Philosophically, there are some advantages to having a brake acting directly on the drum shaft. A user can be assured that the brake is acting on the drum shaft and does not have intermediate links or couplings inbetween.

Interposed brakes

It is also worth considering interposed brakes. These brakes are spring-set and electrically released. The spring-set brake is packaged in a double C-Face housing that has an input sleeve and output shaft with common standard dimensions. These brakes are popular in theatre applications because they are modular and easy to install. It allows a brake to be easily added in the middle of an off-the-shelf motor and gearbox and can be mounted horizontally or vertically.

KEB brakes prevent drama where it isn't wanted
KEB brakes prevent drama where it isn't wanted

KEB (UK) Ltd

5 Morris Close
Park Farm Industrial Estate
Wellingborough
NN8 6XF
UNITED KINGDOM

+44 (0)1933 402220

info@keb.co.uk

www.keb.co.uk

More technical articles
1 week ago
NSK bearings reduce concrete floor manufacturing machine failures to zero
Regular bearing failures in a concrete floor manufacturing machine were leading to extensive downtime, costly lost production, and high maintenance costs. To rectify the problem, the customer turned to the expertise of NSK for a redesigned wheel hub and stub axle assembly.
1 week ago
Servodrives help protect chair castors and cut packaging costs
Drives and motors specialist Yaskawa has played a key role in the development of an automated system specifically designed to fit protective plastic caps onto chair castors, using its Sigma-7 series servo-drives and a SLIO-series controller.
1 week ago
SKF streamlines bearing analysis for Ansys users
With the new SKF Bearing App for Ansys Mechanical, design engineers have instant access to accurate stiffness data on more than 10,000 bearing designations. The app is available in the Ansys Store free of charge.
1 week ago
Omron awarded platinum rating from EcoVadis for sustainability
Omron has been awarded the Platinum rating following a sustainability assessment by EcoVadis. A score earning a Platinum rating, which is the highest distinction, puts the company within the top 1% of all the businesses assessed for sustainability performance.
2 weeks ago
ABB Value Provider wins order for rolling mill DC drive solution
DC drive specialist Iconsys is set to deliver a bespoke drive upgrade solution comprising two 12-pulse drive suites from ABB for a UK steel mill’s payoff and tension reels, used to feed and recoil steel strip through a production line.
2 weeks ago
What are the design considerations when specifying lead screws?
The first in the new ‘Design • Engineer • Build’ series of video podcasts focuses on lead screws – components that are at the heart of countless engineering systems. We talk to Phil Jones at Abssac about the enduring popularity of these essential design products, and the design considerations in their specification.
2 weeks ago
Harting honoured with the ‘Best of Industry Award’
The industry media of the Vogel Communications Group presented their ‘Best of Industry Awards’ shortly before the turn of the year. The Harting Technology Group emerged as the winner in the ‘Electrical Equipment’ category with its Han-Modular Domino modules.
2 weeks ago
Quick ROI and 60% decrease in maintenance travel with remote access
Brazilian surface treatment systems manufacturer Erzinger was keen to limit service trips as much as possible to serve customers faster. By implementing IXON Cloud, it can now support its customers remotely, and work in an intuitive and secure way. It can even set up multiple simultaneous connections to work together on the same project. The result is cost reduction, quick ROI and happier customers.
2 weeks ago
Nord high up in the sustainability ranking
Nord Drivesystems was assessed by the rating agency EcoVadis and awarded the silver sustainability certificate in 2022. In the overall ranking, the North German company is in the top six percent of manufacturers in the industry assessed by EcoVadis.
3 weeks ago
Mitsubishi Electric helps door manufacturer triple its throughput
Renowned door manufacturer Profile Developments has seen a threefold increase in its productivity, thanks to its latest collaboration with Mitsubishi Electric, with a solution based on multiple FR-E series inverter or variable speed drives (VSDs) and other system-matched components, such as a GOT 2000 series HMI and MELSEC iQ-R PLC.

Login / Sign up