 At the curtain call, the handle finally fires the Jack in the Box - revealing a 3-tier white Wedding Cake! Concept was dreamed up by Samal Black the designer. I came on board to work out the mechanism and build it. The difficult parts of the design were making the lid strong enough to take a couple of actors jumping on it, whilst being light enough to be forced open by the (quite hefty) springs. The release mechanism took two designs to get right, and getting the relatively delicate foam/plaster cake up out of the box intact took a few hours of tweaking! Key to the design is the springs being strong enough to throw the lid over the vertical. This causes the self-weight of the lid to hold the whole mechanism in a stable state, holding the cake up. If the lid does not make it over the vertical, the whole lid/cake oscillates and settles at about 45-deg, so the springs are extra tight to make sure that happens every night! The handle is a modified paint-roller, with the kink taken out, the rolled body serves as a winch, generating quite some torque. When taught, a release pin is withdrawn from a locking bar which frees the main sprung cantelever (like a mouse trap) to swing up, popping the lid and raising the cake. A picture or two is worth a thousand words here! For safety we had a couple of locking pins installed along the top edge that were covertly removed the scene before firing. Quick movie showing the mechanism. There are two parallel bars which together keep the cake on the vertical. The two push-bars open the lid so that is just clears the cake on the way up. The whole thing is held sprung by a locking bar (not pictured) from the bottom. The sides/top/lid are all 12mm plywood, with a hardwood veneer, the corner posts are 50x50mm, the minor structural parts are 25x35mm. |