In September 1980, after I had returned from mixing the Led Zeppelin tour in Europe, Jim asked me to come back into his lab and he showed me a setup on his optical bench that consisted of a General Electric Marc 350 metal halide arc lamp and a glass dichroic color filter mounted in front of the lamp. As Jim changed the angle of the filter in the beam, the light would change color. I was really impressed with the color changing ability as that was our dream goal for the gel changer. Jim went on to explain that he had seen the Marc 350 lamp in an UltraArc follow spot, a product that was manufactured by a company owned by John Tedesco, the man who I had met on Jesus Christ Superstar in 1971 and who had consulted with Showco when we started our lighting department in 1972. The Marc 350 had been developed by General Electric as a lamp for 16mm film projectors and it consisted of a 350 watt metal halide glass burner that was axially mounted into a glass reflector with a dichroic coating on the reflector that allowed infrared heat to pass through the reflector and not be projected in the light beam. Jim was fascinated with the Marc 350 because at 350 watts it was three times more efficient and therefore put out the same amount of light as a 1000 watt PAR can but at a higher color temperature of 5,600 degrees Kelvin compared to 3,200 degrees Kelvin for the PAR and without any heat in the Marc 350 beam. {{< StoryImage id="showco-37-ge-marc-350-lamp" title="GE Marc 350 lamp" caption="The GE Marc 350 metal halide arc lamp was rated at 350 watts with a 5,600 degree K color temperature and very good color rendering." credit="Photo lamptech.co.uk" size="medium" >}} The Marc 350 required a special electronic power supply that was large in size and cost $500. The lamp cost $50 had a 50 hour life and could not be dimmed, so the operating cost was $1/Hr. The elliptical reflector of the Marc 350 focused the light down to a small ¾” diameter for the 16mm film gate. Jim placed a piece of gel in front of the Marc 350 and it instantly melted so he ordered some dichroic filters from Edmund Scientific, a hobbyist catalog, to see if they would survive the intensity of the light from the Marc 350. When the filters arrived, Jim found that they easily handled the light intensity from the Marc 350 even when the filters were placed at the focal point of the reflector. Jim knew about dichroic filters from his experience with photography and his use of a 35mm photographic enlarger that used three dichroic filters to balance color temperature. Dichroic filters are pieces of glass that have been coated with materials that have been vaporized in a vacuum chamber and allowed to condense and be deposited on the surface of the glass. The resultant coating is called an interference filter and it passes some wavelengths and reflects other wavelengths based on how it is designed to create a specific color filter. Because a dichroic filter reflects or passes light rather than absorbs light like a gel, it can handle very high power levels. While experimenting with the dichroic filters and the Marc 350 Jim discovered that he could make the color of the filter change by tilting it in the light beam. The color that a dichroic filter projects is dependent on the angle of incidence of the white light hitting the filter and as the angle of incidence changes, the color the filter projects changes. Jim said that he thought he could build a color changing light using the Marc 350 lamp and a number of dichroic filters positioned in front of the Marc 350 where they would twist in and out of the beam. I was very excited about his idea although I was skeptical of the business viability of a $50 undimmable lamp with a 50 hour life that needed a $500 power supply to operate. He asked for twelve weeks to get the prototype working and I approved the project. {{< StoryImage id="showco-38-dichroic-filter" title="Dichroic color filters" caption="Dichroic color filters." credit="Photo from Online edmundoptics.com" size="medium" >}} ### Showco’s Second Eureka Moment #### The Lunch at Salih’s Barbeque September 1980 A few days after my demo with Jim in his lab, we were having lunch at Salih’s, a local barbeque restaurant. The group included me, Jack Maxson, Jim Bornhorst and Tom Littrell, a Showco lighting designer. We were discussing Jim’s idea for a color changing light and Jim said he thought he could make it work with four dichroic filters of different colors mounted on motors in front of the Marc 350 lamp that twisted the filters in and out of the light beam. Suddenly, out of the blue, Maxson casually said, “you know, if you add two more motors you can make it move”. We all sat there in stunned silence as the idea sank in and then Littrell said “yeah and you could add a dimmer and maybe a gobo pattern!’. It was the classic eureka moment and, in that instant, Showco’s Second Eureka Moment, (the first Eureka Moment being the Led Zeppelin show on March 28, 1970), the Showco automated light was born. I asked Jim to add movement and dimming to the prototype and he agreed with the expansion of the the project but he knew that completing it in only twelve weeks would be a challenge. ### Death of John Bonham September 25, 1980 In September 1980 I shipped a small sound system and a monitor system to Shepperton Studios in the UK for four weeks of rehearsals in preparation for a large Led Zeppelin US tour planned for the fall of 1980. A few days after rehearsals had started, on September 25, 1980, John Bonham died from drinking too much alcohol. His death marked the end of Led Zeppelin as a touring group and the end of my career mixing sound for the group. I had worked with John Bonham for 10 years and I was deeply saddened by his passing. I think he is the greatest rock drummer that ever lived. {{< StoryImage id="showco-carl-dunn-photos-zep_3" title="John Bonham" caption="John Bonham Led Zeppelin Dallas Cabana Hotel 1969." credit="Photo Carl Dunn" size="medium" >}} ### End of the Showco Lighting Department October 1, 1980 When I returned to the US after the death of John Bonham, the financial outlook for Showco was critical because we were facing the slow winter months and had counted on the Led Zeppelin US tour to provide the revenues to cover our operating costs. Without those revenues, I had to figure out a way to cut overhead costs even further, so I decided to shut down the Showco lighting department and sell the equipment to raise cash. My plan was to keep our senior lighting designers on a contract basis and sub hire lighting equipment from other companies when we had a tour that required lighting. I was hoping that eventually I could turn our lighting fortunes around and slowly reinvest into lighter and more efficient lighting equipment. I hired Bill Thompson, a former Showco lighting employee, on a commission basis, to help me sell the Showco lighting equipment. Bill successfully negotiated a $100,000 sale of a used Showco lighting system to Jimmy Swaggert, a television evangelist that provided some badly needed cash. ### The Space Frame Truss System {{< MultiGalleryComponent galleries="1980-space-frame-truss" >}} In the summer of 1980, another idea I had to solve our dilemma with obsolete lighting equipment was a new type of lighting truss for constructing lighting rigs. I was casually introduced by a friend and neighbor who happened to be a structural engineer. During our conversation, I mentioned my interest in designing a new generation of lighting trusses for Showco. The engineer suggested the space-frame concept he had used to build roofs of buildings and outdoor spaces. He explained that he had a computer program that would automatically calculate all the stresses in the elements and point-load capacities specified for a space-frame design. I discussed the idea with Ron Fox, and we hired the engineer to help us design a prototype. After several weeks of work, Ron designed and built the prototype space frame. I think it was the most creative achievement among the many amazing creations Ron made during his 10 years at Showco.

{{< StoryImage id="showco-spaceframe-13" caption="Lester Burton walking on a space frame designed by Ron Fox, which utilized identical pyramid-shaped modules fabricated from steel angle and square steel tubing. The modules were connected together along the base by stringers and connected to the plate at the top of the pyramid using ¼-turn load-rated fasteners." credit="Photo Recovered Showco Archive" size="large" >}} {{< StoryImage id="showco-spaceframe-14" caption="Detail of the top plate of the pyramid shaped module of the space frame with the four legs of the pyramid welded to the plate and the individual spanner pieces that connected the pyramid modules together connected to the top plate with a locating pin and quarter turn fastener." credit="Photo Recovered Showco Archive" size="large" >}} {{< StoryImage id="showco-spaceframe-15" caption="Closeup of the ¼ turn load rated fasteners that were used to connect the pyramid modules and spanning pieces of the space frame together to make a flat solid structure." credit="Photo Recovered Showco Archive" size="large" >}} {{< StoryImage id="showco-spaceframe-4" caption="The space frame pyramid modules arranged in a truss-like structure. Unfortunately, when configured in this manner, the single row structure had no torsion resistance and easily twisted." credit="Photo Recovered Showco Archive" size="large" >}} {{< StoryImage id="showco-spaceframe-6" caption="Rusty Brutsche, Eric Pearce from Showlites and Ron Fox discussing an alternative configuration of the space frame pyramid modules. This structure was much more stable than the single truss configuration and did not twist." credit="Photo Recovered Showco Archive" size="large" >}} {{< StoryImage id="showco-spaceframe-3" caption="Ron Fox with his creation. The space frame collapsed into an incredibly small package for transport in a truck and required much less truck space that traditional truss sections. Ron did many incredible things during his 10+ years at Showco but I think the space frame was his single most creative achievement." credit="Photo Recovered Showco Archive" size="large" >}}

I was seriously considering using the space frame for the 1980 Led Zeppelin 1980 fall and winter US tour which was cancelled after the death of John Bonham. We had concerns about the setup time and safety requirements of the system but I felt the space frame concept had great potential. After we shut the lighting department down on October 1, 1980, I negotiated an agreement with Eric Pierce for Showlites to provide conventional lighting equipment for Showco tours and I showed the space frame prototype to Eric. He liked the concept but felt that his triangular shaped aluminum trusses were a better solution for large lighting rigs. So the space frame concept was abandoned and not pursued any further. The agreement with Showlites did not work out successfully and did not last very long.

Showco History