Shown here is the first iteration of the trailer. The trailer frame has bolt holes about 6 to 8 inches from the front and rear, so I figured I could just make support beams straight across and lay a flat bed over that. I found a decent, lightweight pallet made of pine (I think) down by the lumber yard in our neighborhood. After taking it apart, I figured out that I could make two 32 inch cross beams from the 2×4 base pieces, and up to six 34 inch slats† from the other boards – approx 1x4s.
The cross beams went in pretty well, I used a few washers on the outside, and a rubber washer inside between the frame and 2×4. They were pretty snug, and I secured them with 2.5 inch long deck screws. I screwed the top slats on with 1.25 inch long drywall screws.
I took the trailer on a 3 mile round trip test – riding on the street and concrete bike paths – and it seems to be working great. I plan to build side rails around the bed to create a stable box, and to keep loads from shifting into the wheels.
I need to test it to see how much weight it can actually carry, to see how it effects handling and all that. I’ve got a new hitch on the way too. As a work in progress, it will only become clear through usage whether the screws are sufficient to secure everything, or if I need to upgrade to carriage bolts or another solution.