I have two alum plates (45cm x 20cm x 1mm) that are hinged on the long side with two 30 x 80 hinges (30 x 40 each tang) in the middle, and "L" bracket / 20mm brace at the ends secured with a M4 loc nut and bolt. As you might imagine, however much you tighen the lock nut on the M4 mushroom bolt, it cannot keep the flap up due to the "mechanical advantage" of the plate weight. Or, if tighten to the nth degree to hold plate ... the latter cannot be repositioned!
I have looked at 'stays', but they will only 'lock' in the fully open state, (I need to hold the flap between -90 (closed) to +20 from horizontal)
My idea at present is to construct a stay using two flat alum bars constucted as a "V" with the outer points at around 4" on the unit and barn door, and the pivot at about 7" (ie pointing forwards) The pivot will have a fixed bolt / thumbwheel.
It's this latter part I seek advice on. Even though the surface area will be larger - and so I could use a M6 bolt - is there any action I can take to make the friction grip between the approx 1" diameter area on each bar stronger? (A fibre washer will reduce the contact area of metal, so that might not be an option)
In an ideal World, I'd opt for something like a plastic 'crown' gear fixed on each component. When loosened, you can turn the item to a new angle before re-engaging teeth again. (A system used on some cheap Chinese photo light fittings)