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Sunday, August 21, 2011

More Progress on the Homemade Clock

This was another busy week for me and I didn't get as much done on the clock as I would have liked to but... I did get some things done. In case you are not familiar with what I am doing you can read these posts HERE and HERE and HERE to get an idea. The short description is that I am making a clock that has a stationary hour hand pointing straight up. The face of the clock turns counterclockwise to line the correct and current time up with the hour hand and the minute hand rotates clockwise to indicate the minutes. HERE is a video that I made of the CAD model for this clock running and it shows pretty much how it's going to work. Seems simple enough!
What I got done this week is I made the small discs that the numbers will be attached to by cutting slices of 1-1/4" oak dowel. Obviously I made 12 good ones and a bunch of bad ones that were either too thick or too thin. You can see there in the blue tote bin in the picture below. You can also see in the picture that each disc has a Woodruff key glued to it. The idea is the the Woodruff key will add some weight and keep the numbers on the face of the clock upright because the discs will be allowed to spin relative to the clock face.
Clock Parts, Oak discs with Woodruff keys glued to them
Also in the above picture right below the blue tote is a gearbox and a motor. It's to the left of the wood gear on the back plate for the clock. That is another Tamiya gearbox that I got and used in another clock that I built some time ago. Check out THIS post for details of the gearbox. I picked up several of these gearboxes at a hobby shop that was going out of business so I got them at half price and figured that I would use them at some point. You can never have enough gearboxes I always say!

This is the gearbox and motor that I am going to use to run this clock. I thought that it would be neat to make a gear train for the motor to turn the wood gears that I made but to do that would take a lot of gears. For the motor to have any decent speed control and torque it has to spin at a decent RPM and to drive the wood gears that I made I need to go slow... really slow. Less than one revolution per hour for the minute hand remembering that in this clock the minute hand and the numbers rotate different directions. So the minute hand is rotating slower than a conventional clock.
The Tamiya gearbox is a worm drive gearbox with a 336:1 gear ratio and I'm going to add two more gears to get it to drive the minute hand in the clock so the final ratio will be even higher. The wood gears of course at that point will then drive the face of the clock if everything works right.
The other thing that I also got done this week was I drilled the 12 holes for the numbered discs and glued in some nylon shoulder bushings.
Clock face with some bushings installed
Above is a picture of the face of the clock with a few of the bushings installed and others rolling around on the face. I haven't decided yet how I'm going to attach the numbered discs to the face of the clock but I am sure that the nylon bushings will be needed because I glued them in! Somehow I'm planning on attaching shafts to the numbered discs and letting them turn in the bushings.
When I figure that out I'll write more about it. This clock is a fun project but I will be happy when it's dome and I can move on to other stuff.

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