Building the Marimba - page 6

Support bracket for natural bass resonators.

Support bracket for C#2 and D#2 resonators.

Parts for resonator stoppers (244 pieces). There are two plywood discs, one steel disc, and one latex tubing gasket for each stopper. Discs were cut on a drill press with an adjustable hole cutter. A high speed steel with 2% cobalt tool bit was used to cut the steel discs (even so, the tool required frequent sharpening). All discs were painted with chrome-colored paint.

Parts for a resonator stopper and assembled stopper. The ends of the latex tubing are joined with white electrical tape. Parts are assembled with a 1/4 inch bolt (tapered Phillips head). A1/4 inch stop nut (not visible in photo) holds the steel disc, latex tubing gasket and wood disc together. The stop nut is used to squeeze latex tubing between the discs, and can be adjusted for tight fit in resonator. A light coating of silicone grease is applied to the gasket prior to inserting in the resonator. The grease helps to insure an airtight fit. The remaining wood disc is attached flush to the bottom end of the resonator tube with three screws. A 1/4 inch wing nut ( not visible in photo) is positioned outboard on the bolt and is used to adjust the position of the stopper in the resonator. This stopper design allows for tuning of the resonator. The resonators must be tuned each time there is a change in air temperature (see the physics page for more on this).

Adjustable resonator stoppers installed in resonator tubes.


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