Fig. 5. Revolving wagon showing cam shaft operated caster jacks. structed and tested two revised caster jacks which appear to minimize or eliminate most of the difficulties des· cribed. As mentioned, the most worrisome problem was the relative fragility of the hinge pivot. This has been remedied by the pipe shaft and sleeve configuration shown in Figures 7 and 8. Despite the rather grueling cross axis loads to which these pivots have been subjected in tests, no observable wear or fatigue could be discerned. Apart from the pivot modification, th is caster jack is substan· tially the reinforced version used in the Feydeau production. It should be further noted, that in contrast to the arrangement used in the turntable wagon, the use of a second shaft as a pivot means that it is no longer necessary to place the caster jack at the right angle intersection of frame members. Fig. 6. Damaged caster jack which has been bent out of engagement with cam. I USITT I The rather different solution shown in Figures 9 and 10, appears to solve most of the remaining problems. He.·e cam actuation is replaced by the winch action of a short length of 1/8" diameter aircraft cable wrapped around a 1.315" diameter (1" N.P.S.) pipe. The cable is anchored to the shaft by means of standard 3/8" diameter machine bolts in which a 5/32" hole has been drilled just under the head. The aircraft cable is then squeezed between the bolt head and the shaft thus providing a secure anchor (Figure 11). The outside anchor bolts and washers also serve to prevent the winch shaft from sliding out of the frame. The cable wrap pattern shown is designed to minimize load on the anchor points while preventing the possibility of cable overlap. For this reason slightly oversize anchor bolts are used to help guide the second turn of cable. To avoid possible crushing of the cable between the nut of the outside anchor bolt and the thrust washer the latter has a hole diameter approximately 1/8" larger than the shaft. By this means the cable tends to relieve into the space thus formed (see Figure 10). Notice also that as a further means of protecting the cable from abrasion, the lower corners of both the caster plate and the 1/8" caster plate spacer are chamfered in the vicinity of the cable. For the same reason it is also wise to use the regular .650" maximum dia· meter (9/16" across the flats) hex nuts and to chamfer the exposed corners slightly. Though not absolutely essential it is recommended that a piece of 'h" diameter x ¥,," long round stock be brazed to the head of each anchor bolt to prevent the possibility of the cable binding over the top of the bolt head. This has occasionally been noted in use. 2 To provide for adjustment the cable is oversize about 4 or 5 inches. For optimum operation the caster plate should be clamped firmly to the winch shaft by the cables when the casters are bearing weight. THEATRE DESIGN AND TECHNOLOGY SUMMER. 1977 27