verted casters. We constructed a secure central pivot point and placed idler wheels to work in opposition to the pushing force of our drive mechanism. There was no deflection at our pivot point despite the amount of pushing force provided by the pneumatic cylinder, so we ultimately removed the two idler wheels. Mounting the assembly (Fig. 3) in one of the traps in our stage gave us plenty of room for the whole system and eliminated the need for anyon-stage masking, but the design can easily be modified to sit directly on the stage floor. The cost for all the parts needed for tlus drive totals $1,444. All should be available locally and through suppliers such as Grainger (800-323-0620), McMastel~Carr (708-8330300), and Caster Connection (800-544-8978). Fortunately many of the matelials needed for our drive were in stock and the actual cost to us was less than noted above. *:. 1Support Frame 2 Motor 3 Pneumatic Wheel 4 Linear Shaft 5Turntable (shown transparent) 6 Pillow Block 7 Clevis and Pin 8 Pneumatic Cylinder 9Trap Opening 10 Casters TOP VIEW - RETRACTED SIDE VIEW - RETRACTED TD&T F ALL I 9 9 7 35