DIY Bike Cargo Trailer

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(Click on any pic to view full size) 

Overview: I wanted a semi-secure, waterproof trailer to carry my photo/video gear that I could also easily convert to a flatbed for hauling when security was not an issue. I couldn’t find anything for sale that quite fit, so after looking on the web at various designs I decided build one myself. The box is secured at the inside corners with bolts and wingnuts, making it easy to attach and remove without any tools.


Time to build: Roughly 24 hrs.


Total cost: This is a little difficult to calculate as I used a fair bit of materials that my dad had lying around his shop. Some materials were salvaged and the rest were purchased for roughly $65.


Main components:


The hitch, arm and metal frame: These were salvaged from an old Burley kids trailer that was pretty mangled. We cut the metal tubing of the wrecked trailer about 8” back from where the arm connects to the frame (enough to secure it to the plywood bed). 


The flatbed: This was cut out of 3/8” plywood and reinforced with a second layer around the edges, wheel wells and where the metal frame connects.



The wheels and wheel stays: The wheels were salvaged from old kids bikes (20”) and the wheel stays came from the wrecked Burley trailer.

The box: The box is constructed from 3/8” plywood with angled aluminum at the edges. The top has a rim (.5”X1.5”) and opens on 4 small latches hidden between the lip and the body of the box. The lid locks with two latches and small padlocks.





The Flatbed:  We began by cutting the usable section off the wrecked Burley trailer (hitch, arm and enough of the body to secure to the flatbed). We then cut the main piece of plywood (3/8”) to fit the section of salvaged trailer, knowing the box would eventually sit between the wheels. The full dimensions of the flatbed are 34” (w) X54” (l).  


Next we cut the holes for the wheels out of the plywood. Out of left-over plywood we cut the reinforcement layer and glued it down. Knowing it would take a fair bit of bouncing around, we secured this piece with short screws. We attached the salvaged wheel wells with nuts and bolts and inserted the wheels to make sure they fit properly.


We then secured the salvaged trailer piece to the bottom of the flatbed with short pieces of plumbers strapping and screws. After a quick test ride we rounded the corners (both outside and in the wheel wells) with a small saber saw.





The Box:  We first cut the sides (3/8” plywood) to fit inside the wheels and reach to the front and back edges of the flatbed. Next we secured the corners with 1” angled aluminum and small nuts and bolts. The outer dimensions of the box are 22.75” (w) X 54’ (l) X 18.5” (h).


We then cut the top leaving enough room around the edges to be able to attach the lip (1” X 1.5”) all the way around and still have enough room to easily open and close the lid. The lip is attached with small screws, which we set deep enough to later hide with wood filler and paint.


Next we attached the 4 hinges to the side of the box and then attached the lid to the other end of the hinges. After checking to makes sure it opened and closed easily we attached the latches. 


Next came the hinges at the sides to hold the box top up when open. These were supposed to be able to be set to easily open and close while still holding the lid in the open position but they were difficult to get right so we replaced the small Philips-head screws in the pressure part of the hinge with thumb-screws that can be easily loosened and tightened by hand.


 The final hardware to add were the 4 triangular pieces of wood at the bottom inner corners where the box is secured (long bolts and wingnuts) to the flatbed.

The finishing touches included sanding, puttying up holes and blemishes, painting (one coat of primer and two coats exterior paint) and attaching the reflectors and hooks. 


Final thoughts:  


It’s probably a bit on the heavy side but it rides smooth and gets the job done. I haven’t tried it out yet fully packed but I think it’ll do fine. I have a solid chain that I put through the wheel wells when I need to leave it unattended. I like the overall look but if I were to do it over again I’d probably make it a little smaller and a little less coffin-shaped. At least I didn’t paint it black.


Happy trailer building, Gabe