Sky Rider is pleased to announce the completion of the Building Maintenance Unit (BMU) installation on the two Century Plaza Towers. As previously noted in our February 2014 Newsletter, the towers are 571 feet in height and were completed in 1975. These towers have been a famous part of the West Side sky line since their construction. In the 1980’s detective series, Remington Steele, the towers were depicted as their headquarters. Numerous commercials have been shot using the towers as a backdrop and, most recently, The Green Hornet featured scenes in which the towers appeared prominently.
Because of the triangular footprint of the building and the sloping cut at each corner, the original window washing machine could only access the glass portion of the curtain wall. When it was necessary clean the aluminum corners, outrigger beams and transportable platforms had to be utilized to accomplish the task.
Sky Rider worked with Gondolas in Design (GinD) to design BMU’s that are able to access the entire building, saving substantial window washing and metal cleaning cost. These BMU’s operate on a runway with motorized steering wheels. The BMU may be operated both from the rooftop and from the platform. The controls include platform elevation, platform rotation, raising and lowering of the jib, steering and right and left traverse. Elevation is controlled through a Frequency Inverter that allows ramping of the up and down functions for smooth, jerk-free operation.
The platform is suspended from four wire ropes that are wound on a multi-layer drum. The drum system provides several advantages over a traction hoist system. First, the drum is gentle on the wire ropes providing an extended operating life. Second, because the wire ropes are fixed at both ends, electrical conductors can be placed inside the wire ropes for continuous control communication between the BMU and Platform. This eliminates the need for Hanging control cable, radio frequency or electromagnetic control which is particularly prone to grounding and service interruption. And, finally, the platform will remain relatively level without operator intervention.
The following pictures depict the completed BMU on the rooftop. For more information on the buildings, the following links have been provided:
Figure 1. The completed BMU (One of Two) on the Century Plaza Towers. Note the counter-weighted Jib arms with a rotating spreader bar suspending the platform. The BMU is mounted on a base assembly with eight caster wheels to distribute its load on the existing deck and to contribute to ease of steering and maneuverability.
Figure 2. This Descriptive Drawing of the BMU, is provided for reference to illustrate the various components utilized in in its operation. Note what we refer to as the platform, the component that position workers on the façade, is often referred to as a “cradle”. (click on the image to enlarge)
Figure 3. Shown here in this screen capture from Google Earth, which depicts the unique footprint of the towers.