shou ld th is become necessary. A "WAGON JACK" Another wagon stabilizing device has also found widespread application here at I.U. In contrast to the shaft operated devices described previously, this is an accessory u nit and therefore can be readily attached to already existing wagons. Therein also lie its principle difficulties: (1) in many situations it may be difficult to conceal the hardware while preserving operational access; (2) since this is an accessory it is usually not possible to make it as structurally integral to the wagon frame as was the case with the shaft operated caster jacks. Thus, it is not usually possible to transfer the weight of the wagons totally from the casters to the frames with a consequent reduction in stability. In addition, as mentioned below, readily available materials may limit the precision possible in con· structing this device. Nonetheless, in moderate vibration situations builders may find the following device preferable. For clarity, this device can be termed a "wagon jack" since it works on the wagon frame rather than the caster. The wagon jack is essentially a cam operated barrel bolt (Figures 13 and 14). The "bolt" in this device is a length of '%" diameter round bar stock. The floor end of this core piece is given a blunt point (by turning or grinding) which allows it to dig into the stage floor slightly. The sleeve is '%" N.P.S. pipe. One side of this sleeve has a slot approximately 13/32" wide which is inclined to the Fig. 14. Cam actuated wagon jack in the caster up (wagon locked) position. The basic devices have been modified several times for various special applications. axis at 60°. The ends of the slot are terminated with %" diameter holes. Even though the slot is not a true helix, the form shown is functionally satisfactory and is far easier to fabricate requiring only a hack saw and drill press. Nonetheless the 3/8" bolt that serves as the cam follower is subjected to considerable stress and thus a 5 2 3 4 5 6 3 4 7 )------jc+---~ LEGEND CLEARANCE HOLE IN PLA TFORM LID LID PLATFORM FACING 3/8" BOLTS t='LATFORM F~AME SLOT APPROX. 7/16'x3-1!2" 1I8"x1/2'x1" FLAT BAR STOCK - WELD TO HANDLE SLEEVE ONLY FIG.15 WAGON JACK TELESCOPI 'G I USITT I THEATRE DESIGN AND TECHNOLOGY SUMMER. 1977 WiTH HANDLE 31