Up on the Roof With U2, Part 1


We have seen the photos, watched the videos, and all know that the U2 360° Tour features an immense structure that acts as a sort of roof over the band while supporting most of the lighting and followspots as well as the massive 360° video screen. Inspired by show director/designer Willie Williams and designed by architect Mark Fisher, the unique structure is covered with a tensile membrane of PVC-coated polyester fabric, which was fabricated by Architen Landrell Associates. What many who have seen the show—or the pictures—may not know is what is making the 36 orange colored disks on the exterior surface, referred to as polyps, glow from within and illuminate the tensile fabric roof.

Inside of the polyps, built by Bristol, UK-based Steel Monkey Engineering Ltd., are a ring of custom-built LED luminaires, called U2BE (pronounced you-tube) were designed by Tommy Voeten of New York City-based 1212-Studio, Inc. Underneath each polyp are eight U2BE fixtures, each containing a total of 60W of RGBW LEDs. Frederic Opsomer of Innovative Design, who designed the innovative video screen, brought 1212-Studio into the project to provide the LED lights for the set. Voeten had very little time to design the lights, source the sub-assemblies, and get them all built for the first load-in. In the end, they were able to build nearly a thousand units, allowing each of the three set structures to travel with all of its requisite polyps.

Designed in NYC with custom assemblies from the US, electronics and drivers from the UK, and manufactured and assembled in Belgium—all in just four weeks—the U2BE lights are a fitting example of the tour’s global presence. As the tour moves to US stadiums, I recently spoke with Voeten about his unique U2BE luminaires.

Michael S. Eddy: How did you get involved in the U2 360 Tour?
Tommy Voeten: In the beginning of 2009, I met with Frederic Opsomer of Innovative Design here in New York on a totally separate occasion and had a casual meeting. I showed him what we were doing in the architectural market in terms of design and product implementation. He was very interested, and toward the end of April, he called and said to me, “I need a fixture for the U2 tour.” He needed about 600 fixtures in about three weeks. I told him that it would be hard to find a standard product with the output that they wanted and that I thought they would need a custom design.

MSE: What was your next step in the design process, and what were some of the challenges?
TV: After that call, I spent a week designing like crazy. I did the complete product design. There were a lot of restrictions in terms of time; that was the major challenge. Also, there were size limitations. They wanted them to draw 60W of power and have red, green, and blue LEDs. They needed eight fixtures for each polyp. That was my starting point—60W of power, RGB, and eight had to fit inside the polyp. I got to see the drawings from Mark Fisher and what his intent was with the roof covering. When I saw the drawings, I thought that this is an amazing project. I also knew for sure we would have to build a custom product, because every standard product out there could not do this job. In that week, I designed the product including all of the optical design; I also did a thermal design of the product to make sure that the fixture wouldn’t overheat within the enclosed space and that we could get rid of the heat from 60W of power. Since the show was going to be outdoors in stadiums, the fixtures needed to be waterproof as well, which added an additional complication. In addition to all that, was the very tight manufacturing timeframe of three to four weeks.

MSE: How did you approach these challenges of fixture design and manufacturing?
TV: You have to rethink how you design. You start working with standard raw materials. Instead of castings or extrusions that require tooling that take more than four weeks to produce, you start with tubes that can be machined. You have to keep in mind that all of the sub-contractors that you are going to use have standard machines in their shops. For instance, if you design a product with a 10”-diameter tube, there are only limited companies that can make that, because many don’t have the proper equipment to machine these parts. That was a driving consideration for me, to keep the product within a 3”-diameter, which is a very standard size for CNC machines that can produce in high volume. You also end up with a lot of thermal challenges: How do you get rid of the heat? How do you distribute the heat? In the design process, we used software to simulate thermal loads and positioning of the LEDs for optimal effect. The U2BE has a convection-cooled design without any assistance of fans. The dynamics of the claw structure and the design of the tensile fabric and targeted venting holes create an airflow around and inside the polyps that assists in cooling the fixtures. Besides thermal design of the fixture, Computational Fluid Dynamics analysis gives a good insight in these conditions inside the application. I am pleased we were able to solve that in the design.

MSE: What were your considerations in terms of LED choice and how you arranged them?
TV: I came up with a solution using Philips Lumileds Luxeon Rebel LEDs. I made three groups of RGBW, so it has 24 LEDs in total, six of each color. I spread them over 300mm of space; that would be the total length of the fixture. I also custom designed a reflector to collect as much light as possible from the LEDs. From looking at the drawings from Studio Fisher, I could assume the needed beam angles or at least what I wanted as a distribution for this product. It basically came down to a 20°x60° beam angle. In each fixture, I created three collectors or reflectors to collect as much light as possible resulting in 93% efficiency and great color-mixing, to direct it in a 20°x60° angle, and then have a fully mixed beam coming out of the light. One of my trademarks with my designs is that I don’t want to see multicolored LEDs or dots. We knew that at certain angles, you would be able to see the lighting fixture, so we didn’t want to have the “Smarties” candy effect with all of the RGB pixels, so it was quite important to get a mixed beam outside of the fixture. Also, the angles of where the light would hit the fabric structure were very unusual, some parts would be hit immediately and you didn’t want to wait for a meter before the light output was fully mixed. We wanted the color mix to be instantaneous.

Within that design week, using our in-house rapid prototype machine, I built a plastic prototype of the fixture with an LED board, reflectors and started to do some optical tests. I did measurements to see that everything would fit together before we sent off the drawings to the suppliers.

Stay tuned for Part 2 of this interview.

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