The fan provides resistance for your pedaling by moving air the faster it spins the more air it moves and the more resistance is created. The fan is designed to be completely enclosed except for the side where it draws air in. So far the fan is about half enclosed and we need to make a cover for the top of the fan. This is accomplished with some left over aluminum flashing.
1. Cut a piece of flashing to a rough size larger than you need my fan required a piece 7" wide by 15" long
2. You will need to bend the edges at both ends to a 90 degree angle bending sheet metal is easy as long as you support the edge you want to bend with a metal brake or two pieces of wood and a couple of clamps. Just line up the strips of wood with the mark where you want to make the bend and clamp the wood like a sandwich around the metal. You can use your hands to bend soft or thin metal like aluminum.
3. Start with one end and work your way to the other. Ben one end and hold or clamp it in place while bending the metal around to the other mark it a little over length and cut it off. Then bend it over again and mark your second 90 degree bend at the other end. Using the wood blocks make the bend.
4. Line the aluminum up and mark the cutout to go around the upright support. Cut this out and make sure it fits snug. Once satisfied with the fit nail the flashing down with some short ring nails beginning with one end and moving to the other. Finally go around the edges with a hammer to flatten the edges over making it safe to handle without cutting yourself.
With the flashing in place the fan will now intake air from the side and expel the air at the front under the top of the base.