Intro & Burners   Valves   Control   Gas Supply Gas Valves The whole premise of the grid was that computer software combined with variable flow gas valves would allow "gestures" in flame where the physical force of the gesture would be reflected in size and intensity of the flame it produced. When I started to research variable flow valves, though, I found that they were generally used in factory process control and that they were way too expensive for me to use. I decided to build my own out of ball valves and hobby servos.   It was a royal pain in the ass. I hadn't done enough thinking about how many different machining operations were necessary to make each hybrid valve. The arm on the valve had to be drilled and a plastic cross arm attached so that the servo could apply pressure evenly. The cross arm holes had to precisely match the holes drilled in the valve arm. Easy to say, but not to do in my shade tree machine shop.     The servo mountings were problematic as well. I'd used screwed brass fittings to plumb the grid modules, and that meant that every valve was at a slightly different height. It meant that every servo had to custom mounted so that its rotation was on-axis with the center of the valves stem. By the way, yes that's wood the grid modules are made of. Between the low-heat design of the burners and the copper tops on the modules, wood seemed to be safe to use. The alternative was to make the modules out of welded steel, and I sure didn't want to be lifting and carrying something that heavy! It appears to have been an adequate choice so far. I scorched the paint and a bit of the wood in early tests when the trim setting on the burners hadn't been set correctly, but other than that it's been durable.