From Rob Snyder:
Kent, I recently made a Coroplast handlebar box based on your design and want to share it with you, maybe you would share it on your blog.
Sorry that the narrative below is so long, I am trying to describe the construction in enough detail that someone could build it without pictures.
The main difference between mine and yours is I turned it around, inspired by Emily O’Brien’s Dill Pickle handlebar bag (www.dillpicklegear.com). This gives me more room for my hands and a nice place to put the bike number. There are also some differences in the construction details which I will try to describe here.
I fastened the pieces with Mr. McGroovy’s box rivets(mrmcgroovys.com). Mr. McGroovy also sold me a couple of handy tools, one for cutting the length of the flutes and one for taking the rivets apart.
The overall dimensions are 8” tall (34 flutes) 12” wide and 6” front to back. I was using a large sign so I was able to make the box in 2 pieces but my first attempt was 3 pieces. I started by cutting the bowed piece leaving it longer than the needed 20” and a couple of extra flutes wider so I got a nice smooth bend. I have a roll of printer paper that is about 10” diameter which makes a great form but I think you could just roll it around air. I used a couple of lashing straps to hold it in the roll for a couple of days so it took a set.
For the front, top & bottom I cut an hourglass shape where the top & bottom have a bit of excess and the front (middle of the hourglass) is net at 8x12. The flutes are running across the front so that the bends are with the grain.
A few words about basic techniques. I have a special cutter that follows the flutes, cutting only one face of the material at a time. For cutting across the flutes a utility knife will cut through 1 face and partially through the flutes allowing you to snap the Coroplast. I use the special cutter to then cut the remaining face. Curves are more difficult and I find it helps to have a pattern or at least a steel ruler to use as a guide. Draw the curve you want with a Sharpie, place the ruler on the good side of the line so if you slip, the knife goes into the waste, and make a series of short cuts. The knife will want to follow the flutes so it is best to make light cuts. On concave curves you might even try perforations first.
For holes you can use something as simple as a nail. I tried a leather punch which worked pretty well but I think the Coroplast dulled it. A nail set or similar punch works pretty well but my favorite tool is a soldering iron.
WARNING: I do not know if the fumes from melting the Coroplast are toxic, so use caution. The soldering iron I have is a little small for the rivets but it is easy to enlarge the holes.
Back to building the box. Take the straps off the bent hoop of Coroplast. I now trim the edges so that it is 8” wide (34 flutes) and trim the ends square so that the total length is 20”. Now using a straight edge and a dull tool, crush the Coroplast (across the flutes) 1” in from each end and bend it inward. This 1” flange is where you attach the hoop to the front. I punched the holes through the flange then temporarily held the front to the flange with double-stick tape so I could match the holes into the front. I now temporarily fasten the 2 pieces together. The rivets are difficult to unfasten so you may want to use screws or such. Tape may not be strong enough because the hoop wants to spring out. With the front and hoop attached, fold the top and bottom over.
For the TOP, trace around the outside of the box and cut to the line. You can do this with sturdy shears like tin snips or the utility knife but most household scissors will not do it or will be dulled.
For the BOTTOM, trace around the inside of the box and the layout a parallel curve about 1.25” outside of that. This band will be bent up to attach the bottom of the box to the inside of the hoop. You will need to cut notches to make tabs to fasten. I made a trapezoid template to mark the tabs. 2.5” on the base 1” on the top and 1.25” tall. Leave about .25” from the hinge and trace the template. Starting from both ends and making the center tab a little wider or narrower will make a neater looking job.
Punch holes in the center of the tabs, fold them up and mark the inside of the box. It is hard to punch the box from the inside so I disassembled it and punched the holes where I had marked them. Now you are ready to permanently assemble the box. Once it is assembled, all that is left is to add some straps to attach it to your bike and a bungie to hold the lid closed.
My bike has bullhorn style bars so this method may not work if you have cables coming out of the brake levers (classic non-aero or early brifters). I used a small side release buckle and 2 single bar slides which attach to the box through slots and go over the bars & under the stem. I made the slots by punching a couple of holes and slitting between them and then widened and cleaned up the slot with the soldering iron. The slots are just a single flute wide. The front of the box is supported by a cord on either side which goes through a hole and loops around the handlebars. (On a drop bar bike it would go over the brake levers) the cords are adjusted with a simple toggle grip. Seattle Fabrics on Aurora Ave N. is a great place for buying the webbing & hardware but I think REI and other outdoor stores or sewing shops should have it.
To keep the lid shut I use some elastic cord and loop it around a rivet in the center of the hoop. I attached my cords through holes in the front, near the bottom and secure them inside the box with a knot. I can use the elastic cord to hold a cue sheet on the top and a bike number on the front.
The box is not waterproof so I throw most of the stuff into a stuff sack or plastic bag before putting it in the box. Since the bottom is not waterproof any water that gets in drains out. I drove from Seattle to Everett via I-5 with the bike on the back and the bike sat out in the rain for a couple of hours before driving back. My stuff sack is just an old sleeping bag sack and things were damp but not soaked and most importantly still in the box & on the bike. I have only used it on a couple of rides including Chilly Hilly and it did quite well. (that was the first box which had the lid as a 3rd piece)