SAN FRANCISCO (KPIX 5) – The challenge of washing window on a curved building at about 1,000 feet off the ground is quite the task.
But the job of keeping the exterior of Salesforce Tower clean is made possible with help from a pair of innovative tools.
"Well, when you get this tall in a building like this, you're over 1,000 feet off the ground. It becomes very complicated," said Daniel G. Murtagh, Vice President of Engineering with Boston Properties. "Even the simplest thing becomes very complicated."
The simple thing Murtagh is talking about is cleaning 61 floors worth of windows on the massive tower. To do that, you need the right tool for the job.
The tool has a special name, too.
"BMU is the acronym they use for 'Building Maintenance Unit,'" explained Murtagh.
There are two of the giant robotic arms -- custom built in Germany for use at Salesforce Tower -- now installed on what amounts to a rooftop train track.
"So we have the drive wheels that go on these rails and allow move the BMU around the building," said Murtagh."And then you have telescoping booms that hold you in close and also bring you out to the full width of the building."
And that is the real trick with Salesforce Tower. Because while the building stands tall, its curtain wall does not stand straight.
"Around the 27th floor, the building starts to articulate in and gently roll up towards the tower top," said Murtagh.
The idea of form driving function is important here. For years, we had buildings that looked like old refrigerator boxes which people loved to hate; they were kind of uniform and shapeless.
Now you have a building that has a truly unique shape and that leaves you with a problem. The old way of cleaning a building won't work.
You need to build something entirely new."
"You'd never be able to do this with your traditional scaffold system. So this is the result of that," said Murtagh.
"This building definitely has a unique structure to it," said Benson Construction worker Peter Callos, a member of Glaziers Local 718. "Especially that telescoping in and out; definitely comes in play with this machine."
Now with arms outstretched, you can see the robotic cleaning tools from just about anywhere. But they're actually built to not be seen
"We have an articulating hydraulic arm and lever that -- when it's parked -- will actually crouch the BMU that it's below the top of the curtain wall," said Murtagh.
Even though the robotic arms are unquestionably cool?
"We want 'em tucked away," said Murtagh. "As cool as they are, they need to be hidden so the building can stand as the architecture it represents."
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