How to make a cargo trailer?
I've made several and documented at least some of them:


2 wheel trailer 1.6x1m: http://www.moz.geek.nz/mozbike/build/megatrailer





2 wheel trailer 0.8x0.4m: http://www.moz.geek.nz/mozbike/build/shoptrailer





12 more of the above with a better design


 


a four wheel, inertia braked trailer


 




2 wheel, single sided wheel mount trailer with telescoping drawbar


I much favour the mass produced design because it's easy to weld or braze together and quite robust. The chain-in-spring hitch is reliable and durable and very hard to break (the chain links eventually wear though but that takes years).