I was lusting after a bike trailer (https://goo.gl/foNUyH) for my transportation needs and I could not justify buying it or trying to import it since it was not sold where I live. So here is the solution that I found. Not quite as cool but caries the same amount of weight, looks about the same design wise and uses materials available to me. I have used this for years now and it gets me to the market and back (10 kilometers) nearly every Sunday, I have loaded it with all sorts of things and I have been mostly successful in getting stuff home. I recently had to replace the trailer because the old one had started to fail structurally after 5 years of service.
Step 1: Materials Needed:
To make this happen you will need four things:
A bike cargo rack attached to your bike like this : https://goo.gl/ZPKtc9
This was not a problem for me since I already had one to try to help out with carrying things on my commute.
A shopping trolley like this: https://goo.gl/mzmZzA
Where I live these are everywhere and you don´t need to buy them online, they can be had for less than 10 dollars in the market I go to for the fresh produce. I put a link to amazon version that is more expensive but looks the same. An important issue with the wheels is that the one I have and the the amazon one have a foam wheel, not a hard plastic one. This is important for absorbing small shocks and the ability to follow your bike up on curbs. The Burley Travoy has inflatable wheels and would probably be better . . . but that is not what this instructable is about.
A old inner tube:
available for free nearly everywhere. seriously if you don´t know how to get one run over some nails with your bike and replace the tube with a new one and bam, you have a old inner tube. The tube is flexible enough that it allows the trailer to follow the bike around curves and when wrapped several times if has the strength to pull the trailer. I´m sure other, better systems could be engineered to do the same thing but this is easy and simple and I don't have a 3d printer, a laser cutter or a CNC. Did I mention lightweight?
String to weave a support in the base of the trolley.
I used string cut from a PET bottle using a method like this: https://www.instructables.com/id/PET-Bottle-String-Maker/
Step 2: Making It Happen:
So I had to throw my old trailer away as it was past the point of repair. I went to the market armed with only the bike inner tube and bought a shopping trolley and filled it with lots of fruit and vegetables. I then tied the trolley to the back of the cargo rack with the inner tube, done. Simple instructable really.
Step 3: Final Thoughts
Curbs: If you go slow the trailer will follow you. I usually hop the curb with the front wheel and, stop pedaling and lift the back wheel with my foot on the ground, wait til I feel the trailer hit the curb and pull it over the curb. This method works with heavily laden trailers. I try to keep to the streets when I can though.
Avoid top heavy loads: they want to tip when you go around corners or when you are on a slope.
The string I use to support the base is something I did after heavy loads with a small surface area wanted to go through the bottom frame and drag the bag on the ground. This is not necessary for all loads you can use the trailer for but is a good upgrade.
My new trolley has two different height handles, I use the shorter one to reduce the force applied to the frame of the trolley, they are cheaply made and if you put too much force on them they will bend and once a tube is bent . .. it will never be strong again. I try to get the trolley as vertical as possible without hitting the wheel for this reason.
This is not a child trailer, not even if you put a helmet on them.