Silver soldering zinc-coated steel

The manufacturer's figure is 15kg, which I assume is the nearest whole number. If so, the exact figure is somewhere between 14.5 and 15.5kg.

The video is fascinating, but perhaps my picture has misled you: the shelf is painted MDF, not melamine-faced, which presumably makes a difference to its strength. Another difference is that the test weights were centrally placed whereas the feet of the projector will be close to the rods supporting the shelf.

I suppose the best way to see if the construction will be strong enough is to rig up a test with the temporarily-assembled shelf slung below two battens and close above some suitably padded surface and (gingerly) put the projector itself in place. I might try that today.

Thanks again for your thoughts.

Following much sage advice here (many thanks to everyone who replied) this is the stage I've reached. The shelf is 18mm MDF and the supports are 10mm carriage bolts with the heads ground down to 2mm thick flat discs. The holes in the shelf are drilled out to take the square shanks on the bolts and also further drilled to allow the heads to sink below the surface for eventual filling and painting.

Following much sage advice here (many thanks to everyone who replied) this is the stage I've reached. The shelf is 18mm MDF and the supports are 10mm carriage bolts with the heads ground down to 2mm thick flat discs. The holes in the shelf are drilled out to take the square shanks on the bolts and also further drilled to allow the heads to sink below the surface for eventual filling and painting.

I've no idea why that final image appears so monochromatic. Strange.

Rather than the item itself I suggest some bricks or paving slabs and leave them in place for maybe a day. Worst case may be a creeping failure where the bolts pull through the MDF very slowly with a static load. You probably need to include a factor of safety by loading the shelf to perhaps 2x to 3x the weight of the projector especially as its likely to be living above your head in normal use.

Thanks for that. Presumably you haven't seen my post from earlier today, when I describe a test using the projector. I only left it in situ for a couple of hours, though thinking that was sufficient. I'll see about a longer test.

If you run a Histogram on it, at least here, the download-able picture has a lot of red, the green and blue have subdued histograms.

Yet, the picture does not look excessively red to the eye, so I don't know what that Histogram is telling me.

According to my tools here, the "profile" being used is the tool default, and it has not picked up a colour profile from the picture itself.

Maybe between your camera and your computer, some profile got used which has suppressed green and blue.

Paul

If so, I'm not sure how or when. The previous picture was uploaded from my phone to my PC at the same time as the mono-ish one and transferred to the online site simultaneously with it, and appears in full colour.

Bert

Paul, the strange appearance of the final image apart, do you consider that my test with the actual projector indicates that the design of the shelf, with the supporting bolts recessed, is sound?

Given that the load will be completely stationary and unchanging, is the MDF surrounding the bolts likely to deteriorate or otherwise change over time?

Bert

It looks flat to me, so no sign of stress.

I see what look like air intakes on the side.

Does heat from the projector, exit in the direction of the shelf ?

Or does any exiting hot air, go in a safe direction (out the back, out the top) ?

Paul

If you are worried about the integrity of the MDF you could put a sheet of metal on top of it. ISTM would not be visually intrusive given it doesn't need to extend to the edges of the MDF. I don't know of a "sagometer" to predict deflection in worse case scenario of the MDF disintegrating but gut feeling is not expensive: perhaps aluminium diamond plate?

It is dead flat, as tested against a known-to-be-tru straight edge and also a spirit level.

Those are fan-driven hot air vents on the front sides and there are matching ones at the back. The underside of the projector is solid and doesn't get warm at all in operation.

Bert

I wasn't worried at all before I posted about the idea here, but now...

That's a fascinating notion; thanks. With four holes in the metal no larger than necessary to clear the 10mm bolts, the MDF could vanish entirely and the projector still wouldn't fall.

Excellent suggestion. I'll investigate.

that wont do anything much. Put in on the bottom. MDF is pretty resistant to compression but will stretch..

Thanks. I suppose if the area of the shelf within the supports were to stretch and sag downwards to an enormous extent, that part might fall and take my projector with it. But is that really a likely probability?

What mainly concerns me is a situation where the 15mm thick MDF resting on the bolt heads might deteriorate to the extent that the heads would pass through it. Again though, is that likely?

Bert

No. I have considearble experience of MDF shelving and in general it can end up looking like it was made by Robin Tell long before it actually comes apart. The projector contact points will be near the supports which should reduce the bending moment a lot compared with centre loading it, though

Not unless it gets wet.

Robin Tell? Not a chap (or a lady) I'm familiar with, but I get the point.

I would never say "never" but in any situation where that might happen I suspect there would be greater and more pressing issues to deal with.

Thanks for the reassurance.

Bert

The son of the transgender Robin Hood and the Swiss, William Tell...

And presumably famed throughout history for his lack of constructional skill? Strange how that's passed me by.

Thanks for the explanation.

Bert