BLOG: The Why and How of Gondola Restraint Systems

Gondolas – or cradles – are working platforms attached to a Building Maintenance Unit (BMU). They descent along a facade, transporting window cleaners or maintenance staff. Some gondolas are unrestrained and hang in front of the facade, while others are secured to the facade with a gondola restraint system.

No detailed explanation is needed regarding the ‘why’ of gondola restraint systems – just combine the terms ‘window cleaning’ and ‘wind’ in a Youtube search. The top videos will make it pretty clear: an unrestrained gondola that is gripped by wind results in the most frightening and dangerous situations. Also, a gondola that smashes into the facade can cause major damage.

In an interview with Healthday, the late Jim Willingham (a legend in the American window cleaning industry) once said that wind is a major problem for window cleaners working on high-rise buildings.

Three ways to restrain a gondola

Each of these options has its own benefits and possibilities. Which one of these restraint systems is best suited for a specific project depends on your preferences or requirements, as well as on the contour of the building. We’ll discuss three ways to secure a gondola to the facade:

With wire ropes attached to the facade

Users attach multiple wire ropes to these pins (or stick pins in attachment points) as they work their way down the facade. In this case, the cable(s) of the gondola are secured to the facade at several points. Albeit effective, this method requires manual effort every time the gondola moves up or down.

With a so-called mullion guide

In this case, the gondola moves over rails that can be integrated in the building’s facade. On top of the facade, the gondola is fixed in the rails and is then secured for as long as it moves up and down the building. What’s great about a mullion guide rail, is that it provides maximum stability and requires minimal manual effort.

Wire rope restraint system gondola

Wire Rope Restraint (Click to enlarge)

Mullion Guide Rail (Click to enlarge)

With pins connected to a soft rope system

A soft rope system effectively prevents a gondola from swinging, but it serves another purpose as well: uniquely, it ensures that a gondola can get close to a sloping facade.

In contrast to the other two systems, a soft rope restraint system can secure a gondola which moves horizontally along a facade.

Soft Rope System (Click to enlarge)

Soft Rope System in action (Click to enlarge)

Why opt for a gondola restraint system?

With an unrestrained gondola, working in winds over 14 m/s (wind force 6 on the scale of Beaufort) is not advised. Gondolas which are continuously restrained to the facade, however, are designed for use in winds up to 20 m/s (wind force 8 on the scale of Beaufort). Winds are stronger and more abrupt at great heights, especially around tall objects such as skyscrapers. Nobody wants to be involved in an incident with a swinging gondola, let alone be responsible for the physical and psychological damage.

A restraint system stabilizes a gondola by keeping it at a fixed distance from the facade. In other words: it secures the position of a gondola in relation to the building. Anyone who’s even been inside a gondola at great heights knows that a stable gondola makes a working at height a lot easier, and therefore a lot quicker.

For advice about the restraint system that is best suited for your project, it’s best to contact us directly.