My first aluminium welding project: A projector protector (by alaric)
The Scout group I help out with meets in a hall with a projector suspended from the ceiling, and because of that, we're not allowed to play ball games; the projector's pretty exposed, and one whack from a ball would probably finish it.
So, I offered to make a metal "cage" to go around it, and decided that this would be a good project to learn aluminium welding on. Aluminium doesn't corrode, and is light for its strength; light is important for a thing that will be suspended in the air above children.
Welding aluminium is a bit different to welding steel. It's much more conductive of heat, and has a lower melting point; so when you have the bit you're welding hot enough to melt, that molten puddle spreads quickly. You need a lot of heat as it's being rapidly conducted away from the actual weld, but if you linger, the entire thing you're working on will melt... So, the result is that aluminium welds tend to look rather larger and chunkier than welds in steel, and you need to work quickly!
My plan was to make a wireframe cuboid, out of 10mm aluminium square tubing. I made the top and bottom rectangles, then joined them with verticals. So my first welds were the outer corners of the box, and I quickly found that it was all too easy to melt the entire corner into a puddle - but thankfully, I could then just build the weld metal up again and use my belt sander to flatten the result back into a decent corner. So you can't really tell, but the corners are pretty much solid aluminium now...
I finished it, but then spent quite some time worrying how to actually fix it up there. In the end, I made some L-shaped brackets (with a diagonal brace inside the corner). We fixed these to the pillar supporting the projector with hose clamps, and the bottom of the vertical arms rested nicely on the plate at the bottom of the pillar so it can't possibly slide down. The long arms were then drilled, and holes drilled in the corners of the top rectangle of the cage, so they could be joined by M5 bolts. This arrangement gave us some scope to adjust it as we installed it, which was essential as I didn't have exact measurements for the pillar...
Here's the end result:
The yellowy string stuff is some paracord we added at the last minute, just in case a smaller ball manages to sneak in from the sides.
I grabbed a bit of video of myself and another leader (I was way too nervous to stand up on the wobbly scaffold platform!) figuring out how to attach the thing, but I need a more powerful computer to run Kdenlive so I can properly edit videos into a decent enough state to publish!
Alaric, Metalworking | alaric | 
Mon 5th Feb 2018 10:00 am
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