Suspended shelf construction

or a basic torsion box design - a cut 1/2" ply or softwood timber slats to the required length (say 4 - two for the sides, and two internal braces). Glue them to some 6mm ply. Cust some more for the ends, and some for internal if you need it really stiff on both axis. e.g:

There are a considerable range of projector mounts available - some verging on the industrial and very strong! (e.g. a Chief VCM101B rated for 113kg!)

Some projector manufacturers also recommend certain mounts. Do you have a make/model number for yours, I can look to see if there are any recommended ones.

M12 threaded rod from an electrical wholesaler is very cost effective source IME:

That would certainly solve any possible rigidity problems but I do like the open plan look of my previous effort. And ventilation, or the lack of it, would be troublesome: those projectors generate a fair bit of heat and need a good air flow around them.

That's a neat idea, thanks. It's constructions like that which make me wish I had the workshop facilities that American DIYers appear to take for granted: not only a startlingly full range of saws and shapers all sorts and sizes but also a large free flat space for assemblies.

Drill some largish holes through the torsion box underneath the air grills. However I am sure they are designed to be stood on solid surfaces so airflow should not be an issue

Sorry if I was not very clear, I was actually suggesting the box was just the lower panel (i.e. the strong light weight replacement for a large sheet of ply/mdf etc) - not the whole assembly.

(I drew it "open" so you could see what was inside!)

Torsion box style panels etc are very easy to make from the point of view of tools - anything can cut battens to length, and thin ply.

You do make a good point about having something flat to build on though.

(Although I expect for something in the order of a square meter or so, it won't be that critical)

Serious question, is weight really an issue?

The ceiling joists I dare say will be more than strong enough and a good solid bit of timber wouldn’t look amiss.

Tim

You were perfectly clear. I was simply somewhat stupid.

Bert

You must not have seen my previous answer to that: when you're working on your own and have to hold something up to the ceiling while simultaneously securing it to the joists, weight is most definitely an issue.

Bert

Then perhaps it's just me but I certainly can't produce accurate cuts across battens or dead straight lines in sheet material, at least not to match machine tools. I no longer have a chop saw and I've never owned a table saw, alas.

Bert

You're quite right about the solid surface underneath the unit but air circulation around and above it can be critical.

Bert

No one handy who can help?

Tim

Why a shelf? Why not simply bolt it to the ceiling and give yourself more headroom? A friend has done this, it came with a plate for fine adjustment etc, built in. Brian

Well there are still ways to improve your accuracy. A quick and easy one would be to get (or make) a simple mitre box - basically a U channel of wood with reference cuts in it to guide your saw.

Another technique is the knife wall method. Marking out your cut using a knife rather than a pencil, then using a chisel to pare relief cuts into the waste part of the wood. This creates a very nice "step" you can saw against. Easier to see it done than describe:

Yup, but sometimes simple stuff like a length of rope to hold a free end of something, or a dead man prop[1] can help. Also a board across a couple of step ladders as a temporary staging etc.

Also building stuff so that you can fix a light part, and then hook the heavy bit on after while fixing.

John, thanks for the link and the earlier advice. Over the years I've cobbled together many and various gizmos to compensate for my solitary DIY efforts, most of them at least moderately if temporarily successful, even if I do say so myself.

But when it comes to accurately cutting and shaping, though I've tried almost every hint, tip, and helping aide known to man, I still remain a disgrace to the DIY world.

Thanks for those links, John. Whatever size I end up using I wish I could remember how I attached the bottom shelf in the earlier version with nothing visible on the underside. I suppose I could have used a nut, perhaps with a washer, rebated into the MDF or whatever it was, and then filled the hole flush, but the board looks too thin for that.