Thursday 31 October 2019

"Falling asleep" - Map of gravitational field made from plywood

I've seen some plywood sculptures before and loved the aesthetics. I always wondered why people don't take further advantage of the layering to create visuals like a topographic map (Spoiler: because it's a pain in the ass).  I've needed a bed for a while anyway, and I thought a map would make for a cool headboard. And what's the coolest place of all to map? Outer space, obviously.

Specifically, I wanted to map some gravity wells/equipotential fields. The sun-earth-moon system above would be too difficult to do to scale, not to mention far beyond my physics knowledge to model. I settled on only the earth and the moon, admittedly also very much beyond my physics knowledge.
Before I started any woodworking I had to do some math. I needed to calculate the curve of the well (i.e. how gravitational force would change with distance) in order to know how deep to cut into the headboard. To accomplish this, I made what look like some pretty impressive calculations.

While they may look impressive, all the math above is wrong and I'm not actually smart enough to figure out the solution. So I just made a plot of a pretty curve in Excel and wrote down the line of best fit equation.
Empowered by this equation, I grabbed 4 sheets of cabinet grade plywood to make the headboard. Lowes/HD plywood had too many voids and delaminations, plus cabinet grade has more layers/inch thickness.

These sheets had to be glued into one 3" thick 300 lb behemoth. I didn't have a way to apply enough clamping pressure to laminate such a large area, so I decided to fasten them with screws.

I knew how deep the gravity wells will be at any given radius, so by subtracting that from the total thickness of the boards, I calculated the maximum depth I could sink the screws from the back at each radius without going through the board.

This . . . . did not work so great. But more on that later.

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