AN ADJUSTABLE CASTER BASE DARYL M. WEDWICK SOUTHERN UNIVERSITY The technical requ irements of several one-act productions at North Texas State University presented a unique logistical problem. The plays were scheduled with very brief intermissions between performances of the several scripts and nearly all of the sets made use of differing types of wagons and turntables. The materials budget for the productions was very Iimited although plenty of free student labor was available. Further, the available stock of casters was sufficient to equip only one set at a time. Therefore, it was necessary to find an inexpensive way to switch casters from one wagon to another rapidly without compromising mobility or strength. TECHNICAL REPORTS FRED M. WOLFF The solution was the development of an adjustable caster base wh ich can be used on any wagon framed with 1" or 2" lumber wider than three inches. The wagons used for the NTSU productions had 1" x 6" or 2" x 4" frames. The device also may be adjusted to accommodate a variety of angles between framing members and can be easily and rapidly moved between wagons. The adjustable caster base consists of two overlapping plates with matching bolt holes as shown in Figure 1. The plates were fabricated from 3/16" hot-rolled steel. The top plate has a channel 2 11/16" deep; the channel on the bottom plate is 2%" deep. The difference allows for the thickness of the steel and permits the bottoms of both channels to be equidistant from the floor. The weight of the wagon and the angle between the framing members hold the device in place. However, since the wagon may need to be turned over to install or remove the caster bases, two 1/8" holes were drilled in the exterior of each channel so that it could be nailed to the wagon as shown in Figure 4. The accompanying figures show the adjustable caster base designed for use with a rubber-tired swivel caster. The caster shown measures four inches in diameter and has a top-to-bottom dimension of five inches. The bolt hole diameter is 7/16" which allows the easy insertion and removal of 3/8" x 1%" hex head machine bolts. The centers of the diagonally opposite bolt holes in the swivel plate of the caster are five inches apart; the bolt holes in the overlapping plates are in a five-inch-diameter circle. The original idea was to have four curved slots in each of the plates rather than the twenty-four holes. That idea was abandoned for two reqsons. Cutting the curved slots proved to be more difficult and time-consuming for our technical staff than drilling two dozen holes. It was also suggested that cutting the slots might remove sufficient steel so that the strength of the plate might be compro- l 2 1Y1Ei 7" 1- t ...\ 5" ~\y:~ -------"'-i, ~1 r" :J 4" ~L Fig. 1. Exploded view of adjustable caster base showing overlapping plates and base plate of swivel caster. Drawing by the author. I USITT THEATRE DESIGN AND TECHNOLOGY WINTER. 1977 31