At this point, if the walls of the velomobile are already built up, the trike may be permanently attached to the shell. Use zip ties to attach the boom support, and use #10 screws (or equivalent) to attach the seat supports to the anti-sag bars.







With these supports in place, the trike can actually be ridden! Go ahead; I know you want to!

At this point it's time to drop the trike into its new shell, and see how it fits! You may want someone to help you with this - It can be done by yourself (I should know, I did it over a dozen times) but it sure is awkward. Since the hood sections are not yet attached, the walls spread open nicely, allowing the trike to be dropped in.There are a few different supports that will be needed. The Anti-Sag bars, boom supports and seat supports may be measured out before the sides of the velomobile are installed, which will save you a lot of awkward bending over.The "ribs" on the bottom of the shell are strong, but not strong enough to support the weight of the entire shell without sagging! Two aluminum bars are needed to add a bit of extra strength. These bars span the width of the shell, and are placed along the ribs in front and behind the front wheels.Grab the L-shaped aluminum bars and cut them to length, so they fit in the space inside the shell. Note that the bars will not be same length - mine were about 39" and about 37". Since the actual width of your shell might be a bit different from mine, be sure to measure before cutting.The aluminum bars are fastened to the shell using zip ties. Along the length of each bar, on both faces, drill pairs of holes spaced 1" apart at about 3" intervals. I used a drill press for this task, using a 3/16" drill bit. Clean up the holes with a knife if there are any burrs left on the metal.Remove the trike if it's still in the shell, and lay the bars in place. Using an old soldering iron or a handheld drill, punch a hole through each hole in the bar and through the coroplast. In this way, the holes will be perfectly aligned. Then, loop a zip tie through each pair of holes and tighten. With both sets of L-shaped bars installed, the shell will no longer sag.The boom support is made of a piece of scrap coroplast (there should be enough left from cutting out the pieces). It stretches between the boom of the trike and a section of "rib" that runs down the center of the shell. If you're building your velomobile around a Catrike Expedition, you can use the design in the attached file. Otherwise, you'll need to fashion your own in a similar style.First, prop the velo shell off the ground about 2.25" (I used a few pieces of scrap wood) - this is how far off the ground the shell will be. Then center the trike in the shell. The frame should follow the center rib, and the wheels should be centered in the wheel wells. The distance between the boom and the center rib is the space the support needs to be customized for. Aim for about 6" of material wrapped around the boom, and flare it outwards at the bottom.With a drill or hot soldering iron, make holes for the zip ties to pass through. Don't attach anything yet, however.The seat supports are made of short pieces of flat aluminum bar that connect the seat frame to the anti-sag bar. These pieces should be about 4" long. Drill a hole at either end to accept a #10 (or equivalent) machine screw.Start by clamping a 1" inside diameter rubber-lined P-clamp to the seat supports closest to the ground. Use a flat washer, lock washer and plain nut. Place the trike inside the shell again, and center as precisely as possible. Place the supports between the P-clamp and the anti-sag bar, and determine where an appropriate hole should be drilled in the anti-sag bar. Drill the hole with a hand drill. Note, you may need to remove a zip tie if it is in the way. This is OK, since the screw will hold the coroplast to the bar instead.These four supports must be installed after the tailbox bezel has been glued in place (see the next step). The reason for this is that the spacing between the seat and sides of the shell must first be set. So, go ahead and do that now.These supports are a hybrid of coroplast and aluminum. They look like over-engineered flyswatters. Cut out eight trapezoid shapes from some scrap coroplast. I cut four from black (for the rear axle supports) and four from transluscent (for the upper seat supports). Drill holes as marked using a drill or hot soldering iron. Now, cut out four lengths of flat aluminum bar. Two at about 7", and two at about 9". At one end of each bar, drill holes that correspond to the holes in the coroplast pieces. Then fasten the coroplast pieces to the bars as shown using zip ties.The rear axle supports attach to the rear triangle of the trike close to the rear axle (thus the name), using 1.25" rubber-lined P-clamps. Ensure the rear of the trike is centered with the rear of the shell, and dry-fit the support between the rib along the bottom edge of the shell and the P-clamp. The coroplast end should be pushed onto the rib as far as possible. With a drill or hot soldering iron, transfer the positions of the holes onto the rib. Then, mark where the hole needs to be drilled in the aluminum bar to align with the P-clamp. If the bar ends up being too long, cut off any excess. Do this for both supports.Remove the support and drill the hole in the P-clamp end. Then reinstall the support into the shell, by first threading in the zip ties (this is tricky) and then bolting the P-clamp onto the support. These two supports carry the weight of the rear of the shell, and prevent it from "fish tailing."The upper seat supports are done in a similar manner. This time, the support stretches between a 1" diameter P-clamp mounted on the upper-most part of the seat frame, and a rib that runs along the side of the shell. As with the rear axle supports, center the trike, dry-fit the supports, mark the mounting locations, drill then, and mount with screws and zip ties. The upper seat supports prevent the shell from shifting too far left or right.