This clock has two unique features compared to my other clocks. First, it has no hands. The large outside gear is marked with the hours. It rotates and brings the hour markings to the top where there is a fixed pointer. There are also wooden dots to indicate the quarter hours. The second unique feature is in the battery operated remontoir system. In my other clocks, the rewind motor and batteries are hidden in the clock frame. In this clock the rewind mechanism is in the weight itself. When the weight gets to the bottom, the motor is turned on and the weight climbs up the chain. When it gets to the top, the motor turns off and the weight slowly descends for another 8 hours. The pulley at the bottom of the chain is there only to keep a bit of tension in the chain. The big gear is 30" in diameter and is made in 12 interlocking pieces. The frame, large gear, weight shell and a number of small bits are made out of black walnut. The large circular pendulum, Graham escapement and the remaining gears are made out of baltic birch. The clock has been running without problems since I built it 6 months ago. It keeps excellent time.
Since this video was uploaded there has been some interest in how the rewind system works...
I do not have a video devoted specifically to the auto rewind system that I use so I'll try to describe it in words. I have two different designs that I use. Clocks 6, 7 and 8 use a drive concealed in the clock frame and clock 9 uses a drive built into the weight. In the first arrangement I string the chain similar to the way Huygens did it in the 1600's. It is best seen in the video for clock #7. if you look closely you can see the chain is strung over two idler pulleys at the top. The chain between the pulleys drops down to the rewind drive sprocket. The chain on the other side of the idlers goes down to the weights. The weight on the right is the actual drive weight and the other one is much lighter and is used to keep tension in the chain. Both weights have a pulley on top. the chain between the weights is run up to the center of the clock gear cluster where there is another sprocket. This sprocket is the one that actually runs the clockworks. Going back to the rewind sprocket, the drive motor is buried in the clock frame directly behind the sprocket. The motor is a 6 volt gearmotor that runs at 10 rpm. There is a battery pack that is also concealed inside of the framework. I use 8 AA batteries in a series / parallel arrangement to yield the 6 volts. This motor / battery arrangement will run the clock for well over 1 year. In clock #7 you can see a wood bar near the bottom. This bar is pivoted in the center and operates a cam actuated switch also hidden inside of the clock frame. In operation, as the clock runs, the heavy weight on the right descends while driving the clockworks. At the same time the tension weight on the left rises until it engages the wood bar and actuates the rewind switch. The rewind motor turns on and through the chain arrangement raises the drive weight on the right until it engages the wood bar and shuts off the rewind motor. The motor speed, sprocket size and chain length are selected such that the clock will rewind itself twice a day. The rewind takes about 1 minute.
Clock #9 is the same basic concept except that the chain is a simple loop that runs over the sprocket that runs the clockworks. At the bottom of the loop there is a large weighted pulley that keeps tension on the chain. If you look closely, you can see that the chain runs through the center of the weight. The entire rewind mechanism including the gearmotor, 4 idler pulleys, switch and battery pack is inside of the weight. When the weight reaches the bottom of the chain loop, the switch inside of the weight turns on the rewind motor and the weight climbs up the chain until it gets to the top where the drive is turned off. Like the others, this process occurs about twice per day and takes about 1 minute.
In both methods, there is always tension on the drive side of the chain so there is no interruption in drive torque to the clockworks. The system used in #9 is the first prototype and the weight shell is a little larger than I would like. I have a new design with a different motor and gearing arrangement that will make the weight shell much smaller. I will be using the new design on my next wall clock.
I'm currently working on a mantle clock that will use a magnetically impulsed ratchet for the clockworks drive. This clock has an electronic circuit that employs a precise 1 second time base so the clock will be as accurate as any "quartz clock" and will not require adjustment like a pendulum clock does.
Stay tuned ......
Steve
