OPTIONAL 1I2"DIA.x 3/4" L. BOLT HEAD EXTEN~ONS(SEE TEXT)~---- LEGEND 1 3JS"CASTER PLATE-CHAMFER AS SHOWN 2 1-1/4" N.PS PIVOT SLE~VE 3 1" N.PS PIVOT SHAFT 41" N.PS. WINCH SHAFT 5 3/S"X 2" BOLT 6 1/S"D1AME ER AIRCRAF CAgLE (APPROX27") 71"X2-1/2"X1/S"SP.ACEKON CASTER PlATE (WELD) S 3/S"X2ยท1/2" ANCHOR BOLTS - SE~ TEXT 91/4" DIAMETER HOLES - COUNERSINK NOTE:SOME ITEMS OMI ED FOR CLAR!TY 5 2 BOTTOM design. The winch jack is manifestly simpler to fabricate since no offset is required in the caster plate. Further, since no bends are required it is possible to use a much heavier gauge plate. In the experimental jacks 3/8" thick stock was used instead of the y.," thickness used for the cam operated jacks. The use of the 3/8" thick stock also meant the reinforcing plates were unnecessary thereby further simplifying manufacture. In addition to increased load bearing capacity the winch type jacks offer several substantial operational advantages. Since there is substantially no friction in the cable winding, the very audible scraping sound of the cam is eliminated. Even more important is the fact Fig. 10. Winch shaft operated caster jack in the caster down position. The spacer (bolted in this experimental model) prevents possible crushing of cable between caster plate and shaft. The spacer is item 7 of Fig. 9. I USITT I FIG.9 VIEW WINCH SHAFT QPERATED CASTER JACK that since the caster plate is above the winch shaft, floor clearance for the jacks ceases to be a concern. Another ancillary advantage is that the caster assemblies don't require separate restraint when the wagons are manually lifted off the floor. One of the minor annoyances with the cam jacks is that the cam plates fall down and hang below the platform when the latter is being carried and there is often some difficulty in getting all the jacks back in position as the wagon is lowered to the floor. Some sort of restraint could of course be installed but this is an extra operation which is obviated in the winch type. Not all the advantages are with the winch jacks. Since Fig. 11. Winch operated caster jack in the caster up position (i.e., wagon down). Note bolts used as cable anchors. Extensions on the heads of the anchor bolts were not used in this experimental model but have been found advisable. (see tex t) THEATRE DESIGN AND TECHNOLOGY SUMMER,1977 29