Choosing the WheelsSmall bicycle tires, such as 20-inch tires, would be ideal for a wheel chair. Larger tires (26-inch tires, for example), will get in the way of the arms and will not be comfortable to turn. An alternative is to use small motorcycle tires. The height of the tires needed is based on the height of the person using the wheelchair when he is sitting in it. The tires need to be at a height that is comfortable for pushing or pulling the wheelchair.
Making the AxleYou can join two tires together with a steel pipe that is threaded on both ends. The tires are then placed on either end of the pipe and a washer and nut is used to hold each tire on the pipe. The pipe should be fairly tight inside the tires, but slack enough so that the wheels turn. The length of the pipe is determined by what width the chair needs to be so the person sitting in it is comfortable.
Forming the Seat and Back of the ChairYou can make the seat from 3/4-inch plywood. Cut two pieces to the width and length that is comfortable for the user and screw them into a 2-by-4-inch piece of wood cut the same length as the two pieces of plywood. This would form the seat and the back portions of the chair. You would then screw two pieces of 2-by-4, cut the length of the seat, to the bottom of the seat, lining up the edges, with the 4-inch side extending downward.
Forming the BraceCut four pieces of 2-by-2-inch boards at a height that is comfortable for the user, bearing in mind to include the height of the pipe when the wheels are on the ground. These four pieces are then bolted on to each corner of the 2-by-4s on the bottom of the seat. Then bring the two 2-by-2s on either side of the seat together on the opposite ends with the pipe in the middle. Then bolt these ends to the pipe.
Armrests and Leg RestsYou can make an armrest by screwing two pieces of 1-by-4-inch boards together at right angles. The armrests should not interfere with the wheels turning. Screw them to each front corner of the bottom of the seat and the sides of the back.
For leg rests, screw a 12-inch long 1-by-4 board at right angles to a 2-by-2 board. The length of the 2-by-2 inch board is determined by what is comfortable for the user when sitting in the chair. For added foot rests, screw a 4-by-4-inch square piece of 1-by-4 lumber to the bottom of each leg rest.