Category Archives: 3D
My second attempt at building a gear system.
Individual gears are 1mm pitch, 4mm thick gears, and the whole mechanism steps down from 6 rpm down to 1 revolution per day (with the 80-tooth gear I purchased off of SparkFun). (Without that gear, the last gear in the chain revolves 4 times per day.) This means the last gear in the chain actually is a pinion with a 1mm pitch gear connected to a 32p (32 teeth/diametrical inch pitch) tooth gear.
Things I learned:
I think 3mm is probably the thinnest practical gear I can print. (I’m sure I can print smaller.) Also, my height calculations are not dead on correct; I need to sort out why I have what appears to be about a 1 mm gap. (Though I suspect it’s the washers I’m using between layers; the washers measure only 0.5mm thick, and were advertised as 0.7mm. Five of those puppies with a 0.2mm error gives 1mm.
Meaning “depthing” is something I’m just going to have to do, no matter how well I think everything is measured.
I also need to sort out how I’m going to disengage the gear train for adjusting the time. (Small battery-powered clocks seem to do the trick by overpowering the motor. OTOH, watches appear to use a mechanism which engages or disengages a clutch which then allows the time to be set by rotating the watch stem.) I’m inclined to use something simple, such as a pin which pulls up a set of gears and allows them to rotate freely. (I did a prototype of this here, though it’s poorly executed.)
Purchased one of these synchronous motors which rotate at 6 RPM. (A synchronized motor synchronizes against the line current, which is kept at an accurate 60hz rate to allow its use to synchronize against time keeping devices.)
Built my first gear machine using my gear generation software.
This attaches to the synchronous motor using a specially designed 12 tooth 1mm pitch gear that attaches to the synchronous motor, and uses single-tooth counting gears to step down the rotation rate, so the last gear rotates at 1 revolution per day.
First attempt at designing a gear chain for a clock.
This helped me to resolve a number of bugs with the gear generation software, including bugs with the generation of certain gear shapes, and the generation of the STL files for the spacers that are used to hold the gears in place.