Moon Platform Wrap-up!

This week, wrapping up this (longer than I expected) series on the moon platform for Arabian Nights, we’ll walk through the construction of the moon platform we’ve been looking at, including details about the framing, the pneumatics, and the backup hand-brakes. More importantly, as promised, I’ll include some photos and some drawings.

As you can see from the drawing at left (click to enlarge), the moon platform is raked, which complicates the construction a little bit. Another important element that the designer has asked for are the tubular rings surrounding the moon at the top and bottom. Given the circular cross-section of these rings, we immediately began looking at using schedule 40 black pipe to create these rings—they’d be both structurally strong enough to support the deck, but they’d also be able to serve as a tank for the air supply. As budget conversations progressed, it became clear we couldn’t afford the amount of black pipe we’d need to make this work; we could, however, frame the unit out of 1x1 14 gauge steel tube and create the rings out of polyethylene tubing (rated for 120 psi of air pressure). Initially, the designer had wanted the crescent of the moon to be a clear acrylic, and for lighting to be placed in the moon to cause it to shine from below; again, budget constraints made it impossible to make this happen, and the painters have coated the painting of the crescent moon with a UV-reactive paint.

The section view shows the steel box framing of the platform supports, the tri-swivel casters, the mounting of the pneumatic brakes, the sheet metal facing, and the two polyethylene tubes which serve as the air tank for the braking system. There’s a lot of steel in this unit. One of the reasons for this is that there was relatively little other construction to be done on this production—some custom flattage for a show portal, and some soft-scenery sewing. Had we needed labor for other construction tasks, we would likely have chosen wood construction for the sake of time. (I also had a little bet going with my students that with a limited number of steel-working tools, and a limited number of steel-skilled laborers, steel work becomes a labor bottleneck. They were convinced steel could be just as fast. In the end, I won the bet.)

At right you can see a drawing of the pneumatic system. (David Cermak, one of the technical direction grad students here at Purdue and the ATD on this production, deserves credit for the system design and for this drawing.) The directional control valve is a two-position, solenoid actuated, spring return valve; we’re stealing a handful of amps from the battery-driven power inverter the lighting crew installed to power the rope-light effect inside the wagon.

As I mentioned briefly above, we knew from the beginning we were going to include a back-up hand-powered wagon brake system. (These are installed inside the facing, behind hinged panels which also provide access to the pneumatic and electrical systems for the crew.) This was an important safety consideration: what happens if the battery supplying power to the DCV dies, or if the air tank, somehow, loses enough pressure that it no longer can hold the brakes in place? Somehow, the unit needs to remain solid for the actors performing on it, and the wagon brakes provide for that. (Of course, the wagon brakes cannot apply anywhere near the force the pneumatic brakes can, and consequently the actors need to be aware of the difference when they are performing.

Because the actors move the moon and actuate the brakes, they’ll be trained in using both the pneumatic and the hand-powered brakes. To ensure the performance continues smoothly if, for some reason, the cast needs to transition to the hand brakes mid-performance, we’ll be rehearsing that process during technical rehearsals. Additionally, during dress rehearsals, we’ll simulate the pneumatic system failing without warning. We’ll utilize a trick I learned at USITT a few years ago from an audience member at a panel on automation safety: we’ll give a surreptitious cue to the actor who actuates the pneumatic system, which will indicate to him or her that for the next moon movement, he or she should act as if the pneumatic system doesn’t work. This will allow the rest of the cast to experience the “unexpected” failure of the system, and to learn to react quickly and efficiently to engage the hand brakes.

Scroll through the slideshow below to see pictures of the construction and installation process. Check back for more images as we go into tech this weekend!

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