In this third instalment on self build trailers I'll be simply listing all the links I can find with some thumbnail pictures thrown in to make it look pretty. Most plans seem to be for flatbeds so you'll have to use your imagination if you want something like a box trailer or a vending trailer.
The charity Practical Action raise funds to build trailers for Nepalese villagers to carry produce to market and have more recently built bicycle towed ambulance trailers to take the sick to hospitals which are remote from the villages. The plans for the trailers and some pictures are here. Please donate to this charity. An ambulance bike & trailer costs just £150.
http://www.instructables.com/id/bicycle-trailer./ is a great place to find plans and video's to help you DIY, but this boat trailer (pictured) is about the most whacky (and I thought a canoe trailer was nut's!).
Carry Freedom who build and sell the excellent Y frame trailers pictured in my previous post also have available free plans for the "Bamboo trailer". Once again this design was originally meant to fill a need in Nepal but the remit went further, the trailer had to be buildable and repairable by locals using locally understood tools and materials. Though you could make one in PVC pipe or even aluminium tube.
Talking of Ally-Tube,
http://www.appropedia.org/Backpack_frame_bike_trailer is a page that does exactly what the name suggests. The site is a US one so the costings aren't really valid in the UK but it provides some good ideas for a lightweight trailer.
The International Bicycle Fund Cargo Trailer is designed for Africa and written instructions are on the site. To get the photos and plans you'll have to send a donation (suggested $5) to the IBF.
I hope you've enjoyed the penultimate part of my self-build mini-series. In the final instalment I'll be looking at connections from bikes to trailers. I'd particularly like your solutions to the vexed question of strength, stability security and light-weight . The perfect solution does not seem to exist. Your comments and emails please.
My final offering for this post is the electric push trailer, a monowheel trailer which powers your bike along at up to 30MPH or 20 miles range, though probably not both. Plans for this one are here and I've embedded the YouTube video below.