This project was made for under 30 dollars using mostly found objects. If i had to buy everything i used it would cost around 60.
Step 1: Wheel Base
I have to confess i did not build mine. I got it from Dan who scavenged it from an broken trailer.
This instructable uses a firewood cart, i'm sure you can find other wheel bases to scavenge from.
Step 2: Making the platform Part 1
3 - 30" 2x4s
6 long screws
Drill bits made for drilling metal.
Once you get those, drill holes into the wheel base, making about 6 holes to mount the 2x4s.
Step 3: Making the Platform Part 2
Once you have the holes drilled, mount the 2x4s onto the base making a nice platform.
Step 4: Trailer Hitch Part 1
To build the part that connects to your bicycle take a look at this instructable: No Weld Bike Trailer Hitch
For this step i used:
1 10ft x 1/2" conduit tubing
1 Air hose coupling
6 inches of webbed tubing.
2 hose clamps