by jasonbeyers » Thu Jan 21, 2021 2:03 am
I would strongly caution against hanging a projector from only drywall/sheetrock -- especially if people may be standing below them. Ceiling drywall is not designed to hold weight like that, and I'd say the max safe weight supported by ceiling drywall alone is *zero*. Even mounting that weight to a wall (with drywall only) is questionable.
There will be ceiling joists spaced 16" or 24" apart (spacing may be different outside of US) and you'll want to mount the projectors to those, as they are solid wood or possibly metal. Use a stud finder to locate the joists hidden behind the drywall, and use screws long enough to reach them. You'll only be able to affix two of the projector mount holes to these, since the joists aren't very wide, but you could use drywall anchors for the other holes if you wish. But the real strength will come from the screws in the joists.
You can also mount a safety line/wire to the same joist for extra security. Depending on your locale there may be laws requiring these safety wires anyway, if this is a public venue.
I've also seen plates of plywood attached to the ceiling, spanning multiple joists, and projectors can then be mounted anywhere on that plywood. You could paint the plywood to match the ceiling paint for aesthetics. This same strategy is used to mount really heavy TVs to walls.
Hope that helps!