Here are some of my design drawing for my mark 1 trailer;
Although the idea of a folding trailer and pannier rack could work, it was overly complicated for my project and the amount of moving parts weakened the trailer.
Here are some photos of the mark 1
For the axle and wheels, i used mountain board trucks, but they proved too small and the springs allowing the trucks to turn made the trailer unstable. The idea of the extendable arm worked well but my choice of material was poor, using solid douglas fir meant that the grain weakened the design especially on the pannier rack above.
Because of all these faults i chose to not to fully finish the trailer to give myself more time to start on a new design and i am currently making the mark 2 trailer now using steam bent ash.