Instructables

Step 7: Designing the Frame

Below is the frame design I chose for the pendulum wave. We now have all the geometry that we need in terms of driven dimensions to design the frame. This is 3rd grade math (addition, subtraction).




From the figure, we see that Leg Height must be

Leg Height = L + c + D/2 + t/2 - W/2 + B/2 - W

or 

Leg Height = L + c + D/2 + t/2 - 1.5*W + B/2

where

D is the diameter of the pendulum bob,
t is the arm/rotor/stator thickness,
W is the thickness of the Leg/Width frame supports, and
B is the block height.

For my pendulum wave, I chose the frame beams to have 1"x1" cross sections, so W was 1". I chose each block (B) to be 1.5" in height. This results in:

Leg Height = L + c + D/2 + t/2 - 0.75

For the shorter of the two legs, L is obviously the shortest pendulum length (pendulum #18). For the longer, L corresponds to the longest pendulum (#1).

No explanation needed for the base width:

Base Width = 2*(S+J+t/2+0.5) = 2*(S+J) + t + 1

I chose to use a series of eighteen 0.5"x1"x1.5" blocks to support the pendulums. The nice thing about this is that during construction, each block can be manually adjusted to its required position before being secured. It's a more forgiving approach than trying to cut the entire beam from wood, and looks cooler than using a horizontal beam. With 1"x1" cross-sectional beams, this results in the entire pendulum wave being exactly 20" long, with each short and long leg pair being connected by 18" long beams (1/2"x1"x18" and 1"x1"x18"). The thinner of the two beams backs the release mechanism.

For the pendulums, I chose 1/2" diameter steel balls, giving a 1/2" gap between each pendulum (plenty of clearance).