For the Migration model shown on the home page, the repeat time is 45 seconds.  Over the course of that 45 seconds, the topmost of the twelve elements swings 58 times; the next one down swings 57 times, the next 56 times, and so on down to the bottommost 47 times.The elements are made from aluminum angle by cutting, grinding, pressing, grinding, and polishing.    If the elements are made of brass or steel, they lose amplitude more slowly because of their higher mass, ergo kinetic energy. 
 The strings in the Migration model shown are 0.004” nylon monofilament.  I more commonly use 0.008” polyester.   The strings are attached to both the elements and the frame with UV cured cyanoacrylate.

The most tedious part of making a pendulum wave is in tuning it, i.e., in adjusting the string lengths so that the swinging elements realign after each repeat interval.  For the Migration model, this means the strings need to be adjusted within 0.02 inches to get one good repeat, 0.01 inches for two good repeats. 0.005 inches for three good repeats, and so on.  This assumes that what looks like a good repeat to the eye means the elements are within one tenth of a cycle at the repeat time, e.g., if the target frequency is 57 cycles in 45 seconds, the acceptable range is between 56.95 and 57.05 cycles. Expressed alternatively, if the target time is 45 seconds, the acceptable range is between 44.96 and 45.04  seconds. This agrees with experience.