·        CPVC (Chlorinated Polyvinyl Chloride) ½” tubing (below left), 6 ½" per dynamometer.  Available at hardware stores, and is used for hot-water piping.  Note: ½” PVC tubing is a different size and won’t do.

·        ½” Black Nylon molybdenum filled rod (below right) 5/8" per dynamometer. Available from Small Parts Inc.  (part number O-ZRNY-8) or from McMaster-Carr (part number 8554K1).

·        ½” Delrin Rod (below center) 3/4" per dynamometer.  Available from Small Parts Inc. (part number O-ZRD-8) or from McMaster (part number 8572K55).

·        PVC ½” Threaded female coupling collar (below center); these come in a dual threaded female coupling form.  Available at hardware stores.

·        PVC ½” threaded male coupling (below left). Available at hardware stores.

·        8-32 x 5/8” stainless-steel (or brass) machine screw (below right).  Available at hardware stores or McMaster-Carr.

·        1” diameter Polypropylene balls (below left). Available from Small Parts Inc. (part number O-BPP) and from McMaster-Carr (part number 1974K24)

·        Wiffle Balls (practice golf balls).  Available at golf stores. (below right).

·        Epoxy glue (not 5-minute epoxy).

·        Multi-purpose PVC, CPVC, and ABS cement and purple primer for PVC and CPVC.  Available at hardware or plumbing stores.

·        Izorline 130 lbs test dacron fishing line (right).  Note:  It is our experience that monofilament or thin metal lines are not long-lasting enough for this purpose.

·        Extension springs (right) 0.36" diameter spring, 3.0" long, spring constant 2 N/mm, stainless steel.  Available from Associated Spring/Raymond (part number E03600583000S)

·        Sheet rubber (ours is scrounged from old truck innertubes) to be cut into small pieces (right).