Do you need a “hidden” building maintenance unit (BMU) for your facade access? A roof trolley system (or roof car system) is not visible from the street below when it is not used. Light Roof trolleys from are sometimes confused with big roof car machines, which are crane-like machines with long, often telescopic jibs and the hoist on the roof. However, light roof trolley is a flat machine traversing on two parallel aluminium tracks mounted on top of the roof. This text explains the idea of a light roof trolley, when it should be used and what are the advantages and downsides of a light roof trolley system.
|Roof trolley||Roof machine / Roof car|
What is a light roof trolley?
As I said, a light roof trolley is a flat machine traversing on two parallel rails. The roof trolley consists of one or two suspension jibs. The suspension jibs can be either foldable (with fixed outreach from the wall) or telescopic (adjustable outreach). With both suspension alternatives, the jibs are moved out of sight when the roof trolley is not in use. A BMU cradle (or suspended platform) is hanging from the jibs allowing an easy facade access for window cleaning and maintenance. The roof trolley is always equipped with electrical motors which are controlled from the cradle.
|Roof trolley with single T-shaped suspension jib||Roof trolley with double suspension jib|
When should the roof trolley system be used?
The best thing about roof trolley system is that it is completely hidden on top of the roof when not in use. It cannot be seen from the street below or from neighboring buildings and not even from “miles way” like very often is the case with big roof cars. Also it doesn’t usually increase the height of the building. Secondly the super-light roof trolley system should be used for double facades – the roof trolley system is mounted nicely over the facades. Finally, one of the most important reasons for choosing a roof trolley system is the weight. A roof trolley weighs less than 400 kilos (950 lbs.) and two aluminium tracks are less than 15 kilos (33lbs) per meter. The weight of BMU machines starts from 3000 kilos (6 500 lbs.). This means there is usually no need to plan extra support for the roof – the roof trolley system is therefore suitable for even light roof structures.
|Roof trolley system in use||Roof trolley on double facade|
What are the downsides of a roof trolley system?
As with a monorail system, the hoists are mounted in the platform. This means that the maximum working height is limited by the BMU cradle to 170 meters. For higher buildings a big BMU roof car or multiple small roof trolleys are the correct solution. Also, if the facade is very complicated, the light roof trolley can’t be used as the maximum outreach is usually 1.5 meters. In addition, if there is absolutely no space on the roof, the roof trolley system cannot be used and monorails are the only solution. However, it only requires less than 2 meters space from the parapet. Finally, the suspended BMU cradle is hard to take to the roof of the building, so it usually needs to be stored somewhere on the ground level.