Some day (when I'm rich and famous) I'd like to build a clock from scratch. One question that is bugging me is how the length of the crutch is determined. In a way, the crutch sets the swing distance of the pendulum and also limits the length of the pendulum rod. For example: Too short a crutch and a long rod means no impulse strength (unless you use a lot of power). So, how do you figure the length of the crutch?