Before there were smartphones and electronic digital clocks, people used gravity as the basis for telling time. The gravity clock relies upon a swinging pendulum to keep time. A pendulum swings at a rate that depends upon its weight, as well as the length of the pole, string or chain holding the weight. Building a gravity clock requires some specialized clock parts, but you can create a gravity clock that is either very simple or quite complex.
Cut a rectangular block of wood. The size of the wood is not necessarily that important, but a block that is at least 2 inches thick, 12 inches tall and 6 to 8 inches wide should suffice.
Drill one hole in the center of the board and another about 1 inch from the top corner of the block, if the block were standing upright. Don't drill the holes all the way through; go about halfway into the wood.
Insert a dowel rod about 1 1/2 inches long into the center hole and another about 3 inches long into the top hole. Ensure that these fit snugly and will not fall out. If necessary, insert some wood glue into the hole first.
Insert 24 small screws into the top of a blank music CD. Do this as carefully as possible so that you don't crack the CD. The screws should go around the perimeter of the CD at an equal distance from each other. Think of the first screw at the top as 12 o'clock and each successive screw as a 30-minute increment.
Tie a string with a washer attached to the end of it. Place a small bobbin on the small dowel rod located in the center of the wooden block. It should turn freely. Place your CD or clock face on the end of the dowel rod in front of the bobbin so that the screws face outward.
Wind up the string holding the washer around the bobbin behind the CD. Hold this in place and don't allow it to fall.
Attach a clock escapement used in pendulum clocks over the upper right hand dowel rod. The escapement should hang down so that the one of the pointed ends can be aligned with the screws in the CD. Place a straw or a tightened rubber band around the end of both dowel rods to keep the escapement and the CD from coming off the end of the dowel rod.
Pull the escapement to one side and allow it rock while also letting go of the washer. The escapement should rock from side to side with the side closest to the CD catching the screws as it turns. Time how long it takes your washer to reach the bottom. This will be the increment of time that your clock provides. Label the screws on your CD to appropriately match the time interval.