tec h EXPO 2001 PVC/PAINT ROLLER PNEUMATIC MUFFLER by Loren Schreiber San Diego State University This simple but effective muffler was discovered by accident when I used a mini paint roller for a piston. Pneumatic effects are becoming commonplace on stage, along with the need to quiet the annoying hiss and pops of escaping air. This simple but effective muffler was discovered by accident when I used a mini paint roller for a piston in a crude shop-built pneumatic cylinder. (The cylinder is described in the April 2000 issue of Yale School of Drama's Technical Brief.) Not only did the paint roller make an effective piston, but the soft fibers of the roller coupled with the PVC cylinder acting as an expansion chamber also reduced the pop of the in-rushing air and steadystate hiss to very low levels. A little experimentation revealed that one could add another roller and a little more PVC to increase the muffler's effectiveness at higher pressures. Furthermore, the muffler adds only a little impediment to the flow of air. Unlike other potential muffler packing materials, such as fiberglass insulation or old rags, the paint roller holds its shape and does not end up packed tightly and ineffective at the end of the tube. Construction is simple and makes use of materials found around a typical scene shop. Cut a piece of 14″ Schedule 40 PVC pipe a little longer than a mini paint roller. Cap one end of the pipe with suitable reducing bushings. After inserting the roller into the pipe, cap the other end with a pipe cap drilled to release the air. (Glue the cap and reducing bushings into place with PVC cement, otherwise the roller may be launched like a bullet along with the cap.) Screw a hose barb, Prestolock or similar hose connector into the bushing and the muffler is ready for use. If one "borrows" the paint roller from scenic art, the cost of the muffler will be pennies compared to commercial mufflers costing $15 to $75. PARTS LIST 14″ PVC pipe $3.39 (enough for a dozen mufflers) Coupler .51 Bushing: 14″ to 1″ .57 Bushing: 1″ to 2″ pipe thread .32 Bushing: 2″ pipe to 4″ pipe .87 (brass as built-could be plastic) Pipe cap .58 Paint roller 2.97 (pack of two) Total Cost per muffler $9.21 $4.68 TD & T S U M M E R 2 0 0 1 45