Growing up, I would often visit my grandparents in Dinkytown, the southeast Minneapolis neighborhood near the University of Minnesota that was named after the freshman cap worn there a century ago. I remember seeing students on ten-speeds carrying their stuff in milk crates that they strapped to the rear rack with bungee cords.
Inspired by that image, I wanted something better and more secure. Car drivers can lock things up while running errands, so why should cyclists have to carry everything around with them?
So I designed this sheet metal bike trunk. I sized it to hold two 1-gallon jugs of milk with a little room to spare. Its top angles away from the seat like a saddle does, so nothing rubs against the rider. And its 2 latches will accept 2 padlocks to secure the contents against casual theft.
NOTE: If you like, you can prototype the project in cardboard before going to metal. For more advice on working with sheet metal, see my Retro Racer project (MAKE Volume 11, page 97) and Mister Jalopy’s “Q&D: Holes, Rivets, and Bent Metal” (MAKE Volume 05, page 110).
Download the project templates (PDFs), and print them at full size. Cut them out, and tape them onto the sheet metal using double-sided tape, or else cut holes in the templates and stick masking tape over the holes.
Trace around the edge of each template with a fine permanent marker, and use tinsnips to cut out pieces A1/A2, B1, C1/C2, and D1. Don’t cut apart A1 and A2 or C1 and C2 yet. After cutting, pound flat any uneven edges with a hammer and wood block, and file smooth the sharp edges.
I used shiny aluminum for the “chrome” tail ornament E1, but stainless would also work. I’ve found that aluminum doesn’t pound back flat well, so I cut it out with a Dremel and cutting wheel.
For the base piece (not shown on the templates) cut a 14"x7-1/4" rectangle out of thicker aluminum.
Drill 1/8" holes around the perimeter of body piece A1/A2 as shown on the template. For the 8 oval cutouts in E1, drill holes inside each, then work the shapes out with a file.
Temporarily assemble end caps B1 and C1/C2 to the body A1/A2, clamping them together at the bottom. Fit them at the top and re-drill through one 1/8" hole on each bend plane in A1/A2. Pop-rivet through these holes to hold the pieces in place temporarily, then drill through all the remaining holes.
Drill out the pop-rivets using the same 1/8" bit, pull everything apart, and file down any burrs.