5/29/20240 Comments
I have imported these into Carvewright Designer to compare with the originals, but I have not actually used the DXF files to build a clock. I have since redesigned to the same specifications using LibreCAD to generate DXF files. Step 7: Frame DesignĪs stated earlier, I designed all of the wood parts with Carvewright Designer software. The Radial Vector Generator was also used to design the ratchet wheel. You can use other software to generate the proper gears. Then I used LibreCAD to properly scale the DXF files. I did that, then used Inkscape to convert SVG to DXF. The program can create files in the proprietary Carvewright file format, but also can output in SVG format. There are several gear designer applications available, but I used the Radial Vector Generator program developed by one of the Carvewright users and can be found on the Carvewright User's Forum. I used a pinion of 8 teeth and a wheel of 32 teeth (32/8 = 4) and a pinion of 10 teeth and wheel of 30 teeth (30/10 = 3) to get the 12:1 reduction. The hour hand requires a reduction of 12:1. For this clock I used two sets of gears, one with a pinion of 12 teeth and a wheel of 72 teeth (72/12 = 6) and a pinion of 8 teeth and a wheel of 80 teeth (80/8 = 10) to get the 60:1 reduction. With our ratchet wheel moving at exactly 1 RPM, to get our minute hand to move at 1 revolution per hour we obviously need to reduce the rotation by a factor of 60. We do need to adjust it to get the period in the ballpark of 1 second after that, the electronics vary the swing angle to keep it accurate. The actual length is about 12", but the effective length is determined by the location of the round bob, which can be adjusted up and down on the pendulum. That means that the effective length of the pendulum is 9.78". The electronics adjusts the swing angle to keep timekeeping accurate.įor this clock I used a pendulum period of one second. The Mystery clock is designed to allow the swing angle to be variable and thus is able to compensate for environmental variation. If we vary the swing angle from about 15 degrees to about 25 degrees, we can adjust the period about 1/2%. The larger the swing angle, the longer the period of the pendulum. The period of a pendulum is primarily determined by its effective length, but the swing angle also plays a role. Is there a way to compensate for environmental variation? This little push keeps the pendulum moving.ĭue to variations in temperature and humidity, the period of a pendulum can also vary slightly, resulting in inaccurate timekeeping. The circuit then passes current into the coil, making it an electromagnet to repel the pendulum. This generates a current in the coil, which is detected by a circuit. A magnet in the pendulum swings past a hidden coil. In an electromagnetic pendulum clock the pendulum both regulates and drives the movement. In most pendulum clocks the pendulum regulates the timekeeping, but is driven by other means such as a spring or weights.
This clock uses an electromagnetic pendulum. 1/2" and 3/4" thick hardwoods - I used oak, maple, hickory, and pine.The intent is that you don't simply replicate my design, but perhaps also design your own clock. The Instructable covers not just the build but also the design. There are also a few STL files for carved parts. There are some small differences in the replicated design, so if you use the DXF files you will see some differences from the photos in this Instructable. I have since replicated the design using LibreCAD and InkScape to produce DXF files. I use a Carvewright machine, and used Carvewright Designer software to design the clock. A microcontroller drive circuit makes it very accurate.Īll of the wood parts can be made with a CNC machine. Wood gear clocks can be finicky to get and keep running accurately, but this one is quite robust. But you don’t have to tell your guests that – make then guess! I've actually had people believe that this is a perpetual motion machine! The secret is a magnet embedded in the bottom of the pendulum, and an electrical coil hidden in the base. The Mystery Clock is so named because even though the entire clock movement is visible, what keeps it going can be somewhat of a mystery to many.
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