Metronome Engine

myminifactory

I was determined to create a test rig to verify some calculations I made for a compound pendulum, which were intended for a new wooden clock design that I had been working on. The rig's design was based on the engine used in a metronome, as it was the only mechanism I could find that actually utilized a compound pendulum. This turned out to be ideal for 3D printing. The rig is driven by a weight inside a steam engine-style boiler at the end of a stalk, which drives an escape wheel through a gravity ratchet and a couple of gears to provide approximately 2.5 minutes of running time. The compound pendulum controls the rate at which it tick-tocks. Moving the top weight upwards slows down the pendulum, while moving it downwards speeds it up. The top and bottom weights can also be changed out for larger or smaller weights to alter the rate. With all these possible variations, it was straightforward to fine-tune the results to achieve the right combination that could be scaled up for use in a larger wooden clock. This rig could also be modified to include a scale, allowing it to be used as a metronome. As it stands, it is actually a nice little gadget to create on your 3D printer. You will need one of each STL part, except for the following: Spacer 3 requires two parts, Pawl requires four parts, Wedge requires three parts, and Escapement requires two parts that must be solvent bonded back-to-back. To complete the build, you will also need some additional components: * Six roller bearings with diameters of Ø2mm x Ø6mm x 3mm * One piece of Ø1.5mm steel rod for the pendulum * One piece of Ø2mm steel rod for the pendulum pivot * Two pieces of Ø2mm steel rod for the gear shafts * Acetone to solvent bond the frame and other parts together * Ø9.5mm steel balls (catapult ammo) for the weight * Ø12mm brass rod for the weights or washers, weighing 8 grams for the top weight and 23 grams for the bottom weight * A magnet with a diameter of Ø5 x 5mm long to hold the top pendulum weight in position. The STL files for download are grouped into three categories: Blue, Red, and Orange. Use the drawing as a guide to determine where the components fit into the assembly. For more detail, visit http://www.3dprinterclocks.com/page19.html. You can also view a video of the working rig here: