How can I hold an adjustable angle between two load-bearing plates?

Question

I have two wooden plates with the same dimensions (5 cm thick, 50 cm long and 35 cm wide).

The distance between plates must be at least 10 cm. Plate P₁ is fixed but P₂ rotates about the y-axis. Angle alpha can go from 0 degrees (when the plates are parallel) to at least 90 degrees.

How can I realize this design in practice? Which mechanical elements should I use? It must be strong, there will be load of max. 30 kg hanging on plate P₂. There must be some mechanism that will connect these two plates and enable P₂ to rotate but when one sets a desired angle between plates, the mechanism must hold the angle constant.

Answer 1

My First thought is to use a standard hinge, with the hinge itself on the intersecting lines. The plates can mounted with an offset to create your desired gap. Secondly, you need a positioning mechanism. You can use a rotary detent mechanism, for example two disks with radial grooves that interlock in each other when bolted together and can rotate when the bolt is loosened up.

I would not choose a friction mechanism at the rotation axis. The load is large, which creates a strong moment.

Answer 2

I think that easiest way to solve the problem of rotating of plate P₂ will be using a mechanism like this:

To use it, join plate P₁ to an additional plate with length of 10 cm (height and width depends on the dimensions of mechanism) like this:

After join of "unknown element" with P1 and after placing P2 on "unknown element", construction will look like this:

I still need to find way to prevent plate P₂ from falling, I don't think that screws will be enough to attach this mechanism to the plates.