I was looking to make a cargo bike trailer on the cheep. All the items I used are found items except for the $6 box of screws that I needed to buy to complete the project.
Step 1: Gather Up Your Parts
For this project I used two front wheels off of kids bikes.
Metal tubing from three different broken lawn chairs.
Right angel aluminum.
Left over wood.
Step 2: Building the Frame.
This part of the project will take the most time. It will take sometime to come up with a good layout for your frame. It will depend on the size of the wheels that your going to use and the size of bike that you intend to use with your trailer. The size and shape of your found material will also be a big factor in your design. Layout all your tubing and attach with self tapping metal screws. I used some smaller tubing that you don't see, its slipped inside some other the larger tubing for support.
Step 3: Making the Wheel Mounts, and Trailer Mount
I used some right angle aluminum. I cut the pieces down to size. I drilled three holes, one for the wheel and two holes for mounting. I mounted the wheels with self tapping metal screws.
The trailer mount is a right angle piece of aluminum bolted to the bike wheel, I drilled one hole into the aluminum to accept a half loop from the extended part of the from. The half loop allows the trailer to bend when the bike moves.
Step 4: Making the Box.
I cut a piece of plywood to the shape of the bottom of the frame. I made a basic box using some leftover wood. I used two 2x2 pieces of wood for support on the inside of the box. I then painted the box. I added three bike reflectors. I added some hardware so that I could hook some bungee cords to the box.