The inspiration for this DIY project is the wonderful Burley Travoy, an urban bike trailer that doubles as a hand truck -- very useful for example when you are out shopping.
I wanted something similar, but at a sub-50 USD cost. (The Travoy retails at 250 USD and up.)
I used the following, all of which are likely available at most hardware stores:
- a lightweight, foldable hand truck (rated to carry up to 60 lbs)
- a castor wheel assembly
- a bunch of nuts and bolts
- a bike chain, or carabiner, or padlock
The bike I use has a rear rack -- this was where I mounted the trailer hitch.
- the trailer is lightweight and foldable (I can even strap it onto the bike rack when it is not being used)
- the hitching process is quite quick and easy
- the trailer is quite stable when loaded and when on reasonably maintained streets
- because of its lightness, and because of the small wheels and relatively narrow base, the trailer is not so stable when not carrying anything and when on bumpy roads
- may not be so visible to cars because of its low profile -- a visibility hack may be in order
Step 1: Trailer Hitch
I wanted the hitch to handle well, taking into consideration the bike's characteristics. Since the bike leans into turns, I wanted the hitch to be able to swivel, in such a way that the handle of the trailer/hand truck remains parallel to the ground throughout the ride.
I used a castor wheel assembly to serve as the hitch. I removed the wheel, and replaced the stainless steel nuts and bolt that had served as the axle. The cargo trailer would hitch onto the bolt.
To mount the hitch onto the rack, I "sandwiched" the rack in between the castor wheel assembly and another surface. The "bread" were connected by a system of nuts and bolts. (See picture)
Initially I had connected the hitch where the rack had mounting points for reflectors. However, I decided that the weld connecting that mounting area to the rest of the rack had looked a bit flimsy, so I just mounted the hitch to the rack itself.
Step 2: Connecting Facility on the Handlebar of the Cargo Trailer/Hand Truck
First, I used a bike chain. I just wrapped the chain around both the handlebar of the trailer and the hitch. It worked well enough, but I decided that it was too bulky, and I was concerned about having inopportune slacks especially when pulling something in the heavy side.
Next, I used a carabiner. I just connected the carabiner onto the bar, and whenever I would need to attach the trailer to the bike, all I have to do is hook the carabiner onto the hitch.
Now, I'm using a padlock. It works similar to the carabiner, but is less likely to open unintentionally.