What does a clockwork machine do?

A set of gears through which the spring's energy is released. The gears control how quickly (or slowly) a clockwork machine can do things, but they also control how much force it can produce (for climbing inclines, perhaps). A mechanism the gears drive that makes the device do useful or interesting things.

How does a wind-up clock work?

Wind-up clocks utilize a spring for power. The spring is “wound-up” as a store of energy. The unwinding of the spring is what powers the clockworks. Volumes of scholarly research have been devoted to horological gear theory, much of it quite mathematically complex.

How does A Clockwork tank work?

Something like a clockwork tank would use gears the opposite way so it can climb over obstacles: in this case, the wheels (or tracks) would take power from the spring, step down the speed, and generate more climbing force at the same time (like the low gears you'd use on a bicycle or a car for climbing a hill).

Are clockwork toys any good?

Clockwork toys aren't anything like as well made (or as impressive) and if you get more than a minute or two's entertainment for your thirty seconds or so of winding you're doing well. Generally, more interesting clockwork devices that run for longer have bigger and sturdier springs capable of storing much more energy.

How do weight-driven clocks work?

Weight-driven clocks use the gravitational pull of a weight for power. A primary weight is lifted with a counter-weight as a store of energy. Then the gravitation pull on the primary weight powers the gears in the clock. Here’s a great video demonstration of their workings:

How did Clockwork become a standard technology?

Up to the 15th century, clockwork was driven by water, weights, or other roundabout, relatively primitive means, but in 1430 a clock was presented to Philip the Good, Duke of Burgundy, that was driven by a spring. This became a standard technology along with weight-driven movements.