As the ideas for the garden coalesce and become cemented, it becomes time for actual planning. That means drawings, measurements and maths. I’m lucky, I love maths (and drawing).
I’ve gone through fourteen pages of sketches, starting off with sixteen planks for the grass with an additional two on either end for the larger flowers, and eventually settling on eight 12″x12″ plywood planks (keeping the two stationary 6″x24″ ones on the end). The paring down is in consideration of size and complexity.
A 30″ height of the base is the same height as an average desk, which seems a good starting point. The grass and flowers will extend another 18″ above that, making it easy to interact with.
There’ll be three plywood sheets for stability and fifteen stacks of 4x4s to hold it up. I won’t go into the nitty gritty details, but you can get the idea from the pictures. The plywood sheets will be given curved sides so that paperboard can be nailed to them and hold the curve.
I’ll use DC motors (servo motors, although precise, are also really noisy). Because of the structure’s supports, there won’t be an excess of room to work with between the upper plywood and the planks. I do some trigonometry, knowing that I want the edges of the boards to rise about 2.5″. I have to play with a couple variables to find out an ideal configuration that gives a reasonable length of arm and a reasonable size of motor horn.
I find that an arm of length 3.75″ and a horn with a radius of 1.2″ centred 0.98″ from the middle of the plank will give the desired lift and still fit under the structure.
The final component to figure out is the base that people will approach on. There’ll be a couple of load cells to sense the force of people standing on top of the base. It has to be big enough for a few people so it will extend 2.5′ on either side of the structure, making the entire thing a grand 7’x 5.67′. I’ll use some thick plywood for the top of the base and 2x6s for the edge. In the middle I’ll use 2x4s so that there’s some clearance between the load cell and the wood, until people step on it. Since wood is quite soft, there’ll need to be steel plates on the wood where it touches the load cell. Sounds solid.
Now it’s on to testing some of these ideas…