NavList:

So not lego, Frank, but a tidal prediction machine made of javascript:
https://navlist.net/imgx/Tide-Machine-Animation-Chris-Johnson-2016.html

I used this in a talk to 12 and 13 year old kids recently on Fourier analysis.

Originally it was a java animation in an article on the American Maths Society web site.
https://www.ams.org/publicoutreach/feature-column/fcarc-tidesiii3
But Java doesn't usually work in browsers now, and a colleague Chris Johnson reimplemented it in javascript. You can type in your own coefficients if you have a basic knowledge of javascript.

What I love about this family of machines is the use of string to add mechanically. As it can reproduce any finite sum of sinusoidal components with rationally related periods ("trigonometric polynomials") I presume the same system could be used for other astronomical predictions. My limited understanding of the Antikythera mechanism is that it just has gears, so computes rational ratios. It could have done so much more with string! Well of course the string would have rotted so maybe it did.

Bill