Measure the seat and down tubes and the center and left side of your crank spindle. Start with a 6 x 15 inch blank of 1/2 inch birch plywood. Mark a line dividing the 15 inch dimension in half. Hold the marked side of the blank against the left side of a standard men's frame bicycle. Align the mark with the bottom bracket so the blank is evenly positioned on the seat and down tubes. Move the blank towards or away from the bottom bracket along the line so that the edges of the seat and down tubes hit the corners of the blank. Mark lines from the corners of the blank along the seat and down tubes. Remove the blank from the bicycle. Mark a circled D on the down tube line and a circled S on the seat tube line. Measure the down and seat tubes. Lay out the down and seat tube sizes centered on the S and D lines. Compute the variation in distance required to make the drive chain with the 8 tooth pinion and the chain wheel matching your right side largest chain wheel vary by two links or one inch. Use the equation 2 in Section 7 of Industrial Antiquity - Line Shaft Pulleys and Belting, at http://old-engine.com/belts.htm or another Internet resource. Or use 9/16 inch, which I figured for a center to center distance of 7 inches, and a 48 tooth chain wheel. Lay out half the play along a line parallel to the play from each side of the down and seat tube lines. This is parallel to the first line drawn on the board. Lay out lines through the play allowance parallel to the S and D lines. Lay out an additional ten percent to the side of each line. Cut along the outer lines, mitering the ends of the board. Lay out two slots along the innermost lines 1/2 an inch in from the upper edges. Lay out lines perpendicular to the innermost lines passing through the lower corners. Lay out two slots 1/4 inch from the laid out intersections adjacent the innermost lines. Make a drill jig from thin steel. Lay out five 3/32 holes in a 1/2 inch line. Drill all five holes. Make sure they are spaced evenly and are in a straight line. Tape the drill jig on the board adjacent the innermost lines. Drill the five holes through to make a slot. Break the webs with a jigsaw blade. Lower the 3/32 inch bit slowly and use it as a milling cutter to clean out the slots as you move the board by hand. Drill the other three slots the same way. Drill a few lashing holes along the top edge of the board. Lay out a point in the center of the board. Lay out the four motor mounting holes in a centered cross. Drill four 1/4 inch holes as laid out. Center punch the center hole. Predrill the center hole to 3/32 inch. Cut a 4 1/2 inch hole on the center hole laid out using a hole saw. Plane crooked edges, rasp, file, and sand burrs. Use a tack rag to clean the board. Varnish the board on the unmarked side and decoupage the logo in place. Lay out the center of the cap end. Cut a large center hole in the cap to clear the cog. Using the drill jig, drill four 1/4 inch holes. Put a 1/4 inch screw through each hole as it is drilled. Drill four 9/32 or 7.2mm motor mounting holes. These are the radius of the thumb screw shank plus the radius of the bearing head. This allows the motor to mount freely without any holes being uncovered. Measure the distance from the down and seat tubes to the outside of the left side chainwheel and average the two, or use the given spindle and tube dimensions in combination with the tandem crank chain wheel offset to determine this distance. Subtract half the chainwheel thickness. Add one millimeter, which is half the thickness of the pinion cog. Subtract the distance from the face of the motor to the outer face of the pinion cog. Add the thickness of the cap end. Mark and cut the cap, and file it flat to the resulting dimension, square to a the cap axis. Sand the cut cap surface flat. Deburr it. Drill nail holes in the cap 1/4 inch from the end. Use three or four or six or eight holes. Put the board on waxed paper with the marked side down. Glue the cap into the hole by rotating it very slowly while applying a slow drying glue like Welbond white glue. Watch the glue come out the nail holes and along the waxed paper. Position the four motor mount holes in a cross with one hole nearest the lower edge, making the cross square with the long sides of the board. Allow the joint to dry. Nail the cap to the board using the nail holes. Mount the board and cap to the bicycle with four hose clamps. Trim the protruding ends of the hose clamps. Remove the hose clamps from the down tube. Mark the hose clamps D with a letter stamp or engraver. Remove the hose clamps from the seat tube. Mark the hose clamps S with a letter stamp or engraver. File the ends of the hose clamps smooth with rounded corners. Loosely remount the board and cap using the clamps marked S and D on the seat and down tubes, respectively. Mount the motor with the thumb screws. Make a loop of chain to fit the chain wheel and cog. Adjust the position of the board so the chain is tight. Use the lashing holes and strings over the top tube. Rotate the cranks and make sure the chain doesn't bind. Tighten the hose clamps a bit. Connect the motor. Run the motor backwards and adjust the board for minimum drag. Use the lashing holes. Use a rubber hammer. Tighten the hose clamps. Connect the motor to an inverter, a battery, or other load or source of power with a switch.