Figure 4 Rear view of bender showing motor, belt and pulley arrangement. SPINDLES AND FORMING ROLLERS All shafts and spindles were of 3/4" cold rolled steel with 1/2" x 2-3/8" diameter flanges brazed part way up the length of the spindle shafts. The rollers were the only part produced in a machine shop. They were turned from 3" round bar stock on a lathe to the approximate radius of the outside of the tubing. Lacking the rather specialized equipment needed for turning precise arcs the profile was roughly fitted using a piece of the conduit as a template. In practice this has proved adequate. To produce as smooth and accurate a hole for the bearings as possible and to reduce the load on our light duty drill press all the 3/4" holes were bored in five steps beginning with an approximately 3/16" pilot drill and finishing with the 3/4" bit. Had a reamer been available greater precision would have been possible; as it was we had to "worry" the 3/4" drill in the hole a bit in order to clear the 3/4" shafts. These "bearings" must be heavily oiled but otherwise have proved serviceable. The one exception was the lower bearing on the high speed counter shaft. The steel on steel bearing froze up after a short time and was replaced by a clumsy but effective brass bearing which was fabricated. The original hole was bored out oversize. A circle of 1/2" steel flat stock approximately 2-1/2" across was also bored out oversize. The hole in the latter was then filled by brazing and finally rebored with the 3/4" drill.' Two mounting holes were then drilled and the piece was bolted onto the surface of the stationary frame bottom plate thereby providing a brass faced bearing at this critical point. No additional trouble has been encountered. An adjustable version of this may be seen in the detail drawings of the "high speed counter shaft" and "adjustable bearings." It may be helpful to mention that one of the assembled frames can be used as a jig for brazing the rollers' flanges onto the spindle shaft. Simply place the shaft in one of the bearing holes and using the top surface of the frame as a square surface for the bottom of the flange, braze the latter in position. MOUNTING The stationary frame was bolted at either end to 2" x 2" x 1/8" angle iron which in turn was suspended via four 5/16" flat head bolts from an "L" shaped piece of 1/8" thick scrap iron approximately 30" x 39" (see Figure 1). The bolts were countersunk nearly flush into the top working surface and threaded into bolts brazed on the underside of the 2" x 2" angle iron. This arrangement allolJl1ed the height of the rollers to be adjusted in relation to the working surface. CONSTRUCTION Most of the information necessary to build this device is shown in the drawings. Minor changes have been made to take advantage of the experience gained with the prototype. A few procedural notes may aid the prospective builder. The layout and drilling of the frame is easily the most critical operation to be performed. The center to center distance of the spindle shafts must be exactly 4" to assure proper gear mesh and yet even here a variation of ± 0.01" is easily tolerable. To assure that all shafts are perpendicular to the frame plates both pairs of plates should be clamped together and drilled simultaneously. The most convenient method we found was to lightly weld the corners and then grind off the welds after the drilling was completed. ~ THEATRE DESIGN AND TECHNOLOGY Figure 5 Side view of bender in operating posItIOn cantilevered off the side of a work bench. DECEMBER. 1972 27