In support of a bicycle workshop I have decided with my friends to build a trailer to carry the tools around the city.
We were not skilled in welding iron frames, but that didn't stop us, and with some advice we succeeded in building a nice, strong, and effective trailer, which remembers me an ancient Roman "biga".
[first two pictures are created with pixlr express]
Step 1: The pieces
We started to cut an old and cheap mountain bike frame, so that we had different measures tubes. As wheels I found a pair of children bike forks, so to have an easy wheel connection and to use 20" wheels, not big as 26" but not as tiny as a cart. The green tube comes from another old bike frame, it has an elliptical section, and it matches very well with forks' heads.
Step 2: The project
As you see the project is quite simple. The forks are horizontal and connected by two little pipes. All this acts as a surface plane, where we will link the toolbox. The main problem in a frame like this is to avoid big leverages on the weld joints, and I planned to stiffen the structure with diagonal pipes for both longitudinal and cross direction. In this way the weak part is the middle section of the vertical pipe, but it proved to be strong enough.