The ups and downs of installing a bespoke lift in Big Ben’s clock tower

What: Bespoke lift design
Where: The Elizabeth Tower, London

Clock keepers and maintenance workers have been scuttling up and down the Big Ben clock tower’s perilous 334-step spiral staircase since it was unveiled in 1859. Now, as part of significant renovation works to restore and upgrade the landmark, two bespoke lifts have been installed to safely transport workers and equipment up to the belfry.

This was no easy feat. The lift design had to contend with the tower’s 0.23° tilt, strict heritage requirements due to its UNESCO Heritage Site and Grade I-listed status, and tight space restrictions. The project hinged on exact dimensions, millimetre tolerances and effective communication between teams.

The main lift is a traction drive passenger lift which serves 11 levels and sits in an existing ventilation shaft. Structural engineers conducted a cloud scan of the 4.9m by 2.4m shaft to map the space and Victorian tie-rods precisely. They created a steel-frame skeleton to support the lift structure while minimising penetration of the historic brick masonry and correcting the slight lean. This gave lift designer SVM Associates tight working parameters.

In standard lifts, the machinery usually sits directly above the car. However, space restrictions meant the machine room had to be located further down and to the side of the shaft. This repositioning required seven pulleys, rather than the standard single, to divert ropes from the head of the shaft down to the machinery. Polymer pulleys were chosen over steel as their lighter weight made them easier to install and more energy efficient. However, the historic tie-rods proved complex. John Newbold of SVM Associates recalls that intricate geometry was required to plan ‘routes’ for the ropes – one clearance is just 2mm.

Although the design and engineering were bespoke, the 13-person lift car was constructed using standard components. This was crucial for proven quality and term-long serviceability. As Newbold asserts, ‘It’s not an architectural nicety, it is a working utility lift that needs to be maintained into the future.’ The mechanical systems are almost maintenance free and individual rope tension is monitored by electronic transducers to prologue life.

The car’s floor plate is as big as the ventilation shaft would allow in order to accommodate a wheelchair and its safe evacuation. Although it is not a fire-fighting lift, it does include features recommended by London Fire Brigade, such as a secondary power supply in case of a mains power failure.

Why a second lift? From the 11th level, the available space narrows and a smaller lift was needed to provide access into the belfry. No machinery could be in the belfry itself; there was no space, it wouldn’t have complied with heritage requirements and there were concerns that the hum would interrupt the BBC’s live recording of the bells’ ‘bongs’. As a result, a 500kg hydraulic platform lift, which is pushed from below, was chosen.

Although the belfry is covered, its sides are open to the elements and all lift equipment and finishes have been waterproofed to prevent rusting from rain and mist. The lift itself is made from 316 grade stainless steel and hot-dipped galvanized steel.

It is no surprise that this was expensive project. The passenger lift cost roughly three times a standard model – although it could have been much more without extensive early engagement between the main restoration contractor Sir Robert McAlpine Projects, lift consultant SVM Associates and supplier Stannah Lifts. That collaboration certainly paid off, ensuring that only millimetre adjustments were made on installation.