Reddit Enhancement SuiteThere are two main forces that you have to deal with to make this clock work:

1. The moment of inertia, aka the Angular Momentum of the sprocket and chain system. Normal clock hands weigh only a few grams, and while they are fairly long (which increases the moment arm) their minimal weight means the clock does not have to exert much force to turn them. They are also typically balanced with the center of gravity being at the axis, which means the force need to turn them does not vary much with the time of day. Our setup is going to weigh significantly more, and have a much higher moment of inertia, requiring significantly more torque to accelerate and decelerate the sprocket for each tick of the clock. This causes the clock to run slow, decreases battery life and potentially increases wear and tear on the delicate parts in the mechanism over time. My plan counteracts this in two ways, first by using a high torque mechanism, designed for large, heavy clock arms. Secondly, I went with a continuous drive version, rather than one which visibly "ticks", which reduces the force required to only that needed to overcome friction, since it is not accelerating and decelerating the sprocket during each tick.

2. Vertical force, perpendicular to the axis, applied downwards at the gear. Here's a diagram I threw together. The Black box is the mechanism, and it is anchored to the large yellow block (the mounting structure of the clock - in this case I'm using wood). As you can see there are three lines extending from the mechanism; these represent the coaxial shafts of the clock - red (hours), green (minutes) and blue (seconds) which normally would have hands fixed to them. For this clock the only one we will be using is the green minute axis, which makes one full rotation each hour. The pink shape is the gear, which is attached to this axis. The part extending above and below represents the teeth, from which the chain will hang. This presents a problem, because the clock was never designed to handle this amount of mass suspended from it. This weight pushes the green minute tube against inside wall of the hour tube (causing friction), and puts a lopsided downward force on the gears within the mechanism, which are only designed to apply rotational force to the axis. The bearing (Grey, around the green minute tube) is there to counteract this force, by supporting the green tube in such a way that it can still rotate freely while holding up the extra weight of the sprocket and chain. Without it, the force caused by these weights would be placed on the clock mechanism and axis, rather than on the surrounding support structure.

Does this make sense?

Furthermore, we do not care about the red and blue hour and second hands, but we need to allow them to rotate freely as well, since they are all geared together within the mechanism. I'm still waiting for my high torque mechanism to arrive, and i'll put it all together at that point. I initially tried just attaching the sprocket to the minute hand of my first mechanism (very cheap, flimsy one made for a wall clock), but the forces described above easily overwhelmed it.