To transport stuff around KÝbenhavn I build a trailer. It is not wholy finished, but good enough to move the bicycle parts from home to the place where I am building my python. The python project got some delay because of it, but OTOH, building the trailing gave me some experience I can use for the python. For example: the importance of jigs.
All of it is from recuperated bicycle parts. The rear fork is from a childrens bicycle. And is simply sticked into a frame tube to form the main carier tube. This is then welded to a head tube to allow me turning around corners. The angle of the head tube is about -80 degrees (didn't bother to actually think about the "optimal" angle, just took something that looked fine). To connect it to my recumbent I welded a shortened down fork onto the stem.
The trailer is really light (1mm tubing). But when loaded with a high load it is too flexible. So I will soon be adding more gramms to stiffen it up.
A quick release of the rear wheel is used but with to extra 10mm thick washers on between the trailer fork rests. The trailer is vertically turnable around these washers. This is the part that is not finished. At the moment one side of the washer is missing and the quick release simple presses on the trailer dropouts. Obviously, this is not a durable solution...
The next step is is to complete the washer, and simply to bind the trailer fork using a nylon rope. When that doesn't work then I will need to make two pins to hold the fork into place (just like is used with the bob trailer).