Building the Wing Assemblies
Each of the tip-up wings have wing supports (pieces 7) that pivot out from the cart on continuous hinges (pieces 9). Cut and sand these support panels, and grab a hacksaw to cut lengths of hinges to suit them. I laid out my hinge cuts first to make sure the endmost holes in the hinge leaves were evenly spaced from both ends. Fasten a hinge to one edge of each support, driving short screws into every hole; orient the knuckles of the hinges flush with the face of the plywood.
Notice in the photos that the lever knob hardware holding the extendable braces up or down mounts on the aluminum T-track (pieces 8). Mark two strips of T-track to length. You can cut it quickly and accurately at the miter saw or table saw, but be sure to wear eye protection to protect against metal shavings. Ease the sharp corners of the tracks with a file, then screw them to the other long edges of the supports. You’re ready to mount the supports to the carcass at this point. Just center the supports front to back on the side panels and flush with the top and bottom edges. Screw them in place. You can face the hinge knuckles forward or backward, depending on how you want the supports to fold up; either way works fine, but arrange both supports to fold in the same direction for convenience.
I made both braces (pieces 10) from a wide piece of scrap maple. Use a dado blade to trim a centered tongue along both edges of the workpiece to fit into the T-track channels. These tongues need only be about 1/16″ long — any longer, and the T-bolts won’t tighten properly inside the tracks. Adjust the width of the tongues a tad narrower than necessary so the braces will slide smoothly up and down in the track channels. Rip both braces free and cut them to final length. Now head to the drill press to bore a 5/16″ centered hole through each brace, 7-1⁄2″ from one end, for the T-bolts. Step to your router table to knock off the long edges and bottom corners of the braces with a 1/8″ roundover bit, and sand them smooth. Install the bolt hardware, and slide the braces into place on the support tracks.
The two wings (pieces 13) start out as square-cornered panels, but I rounded the two outside corners with 1″ radii to make them more “leg friendly” on the final project. Here again, the wings pivot on long hinges (pieces 14), hacksawed to length. I fastened those in place with the wings clamped flat on my bench and the hinges folded open to an “L” shape, with the knuckles facing inward. It kept the hinge hardware flat and aligned, while providing me good backup support when drilling pilot holes and driving all of those little screws! When it comes to hanging the wings, those fancy new pivoting supports and braces won’t help you yet. Fold them out of the way. Instead, you’ll need to ask a helper to hold the wing hinge leaves against the top panel edges while you drive a screw at each end and one in the center. Check to make sure the wings will be flush with the top panel when tipped up. Once these first few screws are driven, you can fasten it the rest of the way on your own.