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).
<p><a href="http://fy.chalmers.se/%7Ef7xiz/TIF080/pendulum.pdf." rel="nofollow">http://fy.chalmers.se/~f7xiz/TIF080/pendulum.pdf.</a></p><p>it's not available anymore???</p>
<p>I love your top view design! How unique! Have you seen this giant version made by the STEAM Carnival &amp; Two Bit Circus? <iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/YbGev0--ryk" width="500"></iframe>I bet a life-size version of yours would be AMAZING!</p>
<p>How much would you charge to make one of these. my fianc&eacute; loves it. Otherwise I'll make a run to hobby lobby and break out the tools.</p>
Very cool release mechanism. I must say though, all that math is making that sponge thing in my head throb.
Thanks for the feedback! Yes, I was a little worried about posting the math... In hindsight, it might not have been a bad idea to have the last page an appendix of sorts, dedicated solely to math for those interested. I know it's a lot to wade through. <br> <br>Btw, you can always skip directly to the end for the bill of materials :)
And whos says science isn't fun!
Wow! That is amazing! You must be a genius or something with all of that math stuff, but I think I'll just follow your dimensions. This is a great instructable.
Ha, thanks! The dimensions should get you through. If you wait a couple months, I should have another instructable up detailing construction. However, go ahead and give it a try if you want. Feel free to ask if you have any questions!
Beautiful! That's a great science-on-the-beach exhibit :-)
Why thank you! <br> <br>Sand might result in a less-than-best viewing surface, however. ;)