The benefit of the pendulum in a clock was first discovered by the famous astronomer, Galileo. However, before he could put his theory to test, he died. Shortly thereafter, Huygens took Galileo's idea and executed it. The result was the clock pendulum, which would swing back and forth, thus helping the clock keep accurate time. As you can imagine, the clock pendulum is a critical component for this style of clock.
The pendulum clock actually consists of several things. Although we have seen changes in material and technology since the early grandfather clocks, it is important to understand the original design. For instance, the clock would have a face, featuring both minute and hour hand. Depending on the clockmaker, the grandfather clock might also feature a moon phase dial. Then, you have one or more weights and the actual pendulum.
If you were to look at wall pendulum clocks, you would see that the pendulum actually swings every second. However, some of the smaller cuckoo clocks that also feature a pendulum will swing two times per second. Now, when looking at the larger, antique grandfather clocks, the pendulum would swing once every two seconds. The function of all these components all work together to keep the clock running accurate.
The weights of the grandfather clock are also essential, working to make the pendulum swing. These weights work as energy stored up so the clock is capable of running long-term. The way in which the clocks are wound depends on the clock and age of the clock. For instance, a weight-driven clock would be wound by a cord being pulled on to help lift the weight. Now, early on, people tried to make the second hand work like a regular clock's second hand by attaching the weight's cord to a drum. Next, they would attach a second hand to the drum. The problem is that this caused the weights to be released, thus falling and breaking.
The next attempt included putting a friction device on the drum, kind of like a brake so to speak. However, if temperature and humidity were to change, the friction device would also change, meaning the second hand no longer kept good time. Because of the problems, people worked hard in the 1600s to find a way of solving the problem. It was at this time Christian Huygens worked to make the pendulum, the solution that worked.
What Huygens discovered was the length of the pendulum made a difference in how well it kept track due to the force of gravity. Because gravity, as seen on earth is constant, weight would not affect the precision of the pendulum, only the length.