I was lucky to find some 25mm aluminium, square hollow section, and was able to welded it up into a chassis.
Then the base came into my possession part of an old shop sign, 100% waterproof and with a bit of butt jointing I had enough for the base.
Surfing the internet, I found a heavy duty basket about the right size and about half the cost of buying enough material to make one, although I had to travel to get it. This was attached to the floor of the trailer with J bolts, making it east to remove, if required.
There are two ways you can attach the trailer to the bike, (One) at the rear axle – (two) at the seat post, I like the seat post idea for it gives you a handle to push it around with when not on the bike, like a barrow, also there was a lot of fixings and fittings at this point (at the drop outs) on the bike already, mudguards, rear carrier and the axle itself. I also want it to be interchangeable between my bike and my tricycle, and there are no rear drop-outs on a tricycle. One problem I will have to overcome. I had have all this equipment on top of the rear rack, stopped me using the seat post. But I’m sure I can work something out.
I bought a universal joint bracket made to go around the seat post that could be adapted to do the job. Making a handle was a different kettle of fish. If made from metal it would have to be put though rollers, that would mean a visit to a fabricator, the cost of having one made would outweigh the cost of building a DIY trailer, a manufactured trailer from China are very reasonable these days. However I was literally sitting on the answer. I had rescued the chair from a skip, it just so happened to had a lovely curved leg, that flowed into an armrest. Made from wood, so easy to work with, and more importantly, too hand.
Here is how it all ended up, OK a proper manufactured trailer would have looked better, but where is the fun in that? If I don’t count my time it was cheap enough to build since I had the pair of wheels, from some long forgotten project that never made if off the drawing board, and it was good to know I still possess some of my old welding and metalwork skills.
Keep well and safe.