tion was a a right angle to the jacks so that the pipe sleeve pivots would be tested under the most adverse conditions. The wagon was loaded with stage weights which in combination with the estimated weight of the wagon approximated the 200 lb. load ratings of the casters employed. The wagon was then moved back and forth over the test course a total of 50 times or in other words for a total of 100 passes. The clearance above the floor before and after the test and the condition of the jack components were noted. The results were encouraging. The minimum clearance above the floor (under load) was 5/8" both before and after the test. Visual inspection showed no deterioration of jack components. The sole exception was a slight loosening of the cables on the winch jacks probably due to their seating more fully around the holes in the caster plate. The only other failure observed did not concern the jacks but involved badly cracking the wheels of one of the casters. At this writing the winch style caster jacks have been used in performance situations with at least one run requiring well over a hundred scene shifts and with estimated loads per caster over twice that used in the tests just mentioned. The only difficulty encountered has been the problem mentioned earlier involving the cable occasionally binding over the top of an anchor bolt. The Y:!" diameter extension eliminates the problem. Thus is would seem that these jacks are at least as reliable as typical medium duty stage casters. It is probable that other technicians will devise variations that will further increase the load bearing capability Fig. 12. Winch shaft handle lock. a separate lock should not normally be required for the cam operated jacks, the latter can be set more rapidly than the winch type. Also it is probable that most stagehands would be more comfortable with the 90 0 motion of the cam type rather than the 180 0 required by the winch version. TEST RESULTS The author installed both types of jacks in a test wagon in order to examine the durability of these designs. The effects of a rough stage floor were simulated by causing the wagon to roll across a series of five 3/8" thick wood strips spaced approximately 12" to 18" apart. The platform was oriented in such a way that the direction of mo- .I 1/8" L' / I / / ~ \ ~_~~' _ .: -; -----t;,~_. I ~/ 13: " 1321 \ l r I I ; I , -(~'; I : I I ! : I ,-,-__~'---l i LT. SIDE FRONT _ _ _---." DETAIL: CAM f 7-112" 4-112" ! IA3" '( TAP 3/8 -16 --- EIJ- A B C D 30 ~ \ SUMMER,1977 1" NPS. 1" DIA. 116" 1/8" :: 9/16' RT. SIDE ... ... LEGEND I 314"NP.50~ 2 OPTION~L I" 'PS.P!PE CRIMPING (SEE TEXT) 3 3/8 - 16 BOLT NOTE SOME HIDDEN LINES OMITTED FOR CLARITY FIG.13 CAM OPERATED JACK THEATRE DESIGN AND TECHNOLOGY WAGON I USITT I