2. Fabrication

An overview of fabrication steps for building the gear box are as follows. 

1. Based on the speed settings desired, the number of gears needed and their respective diameters must be determined. Paper cutouts for each diameter size are made. 
2. The paper cutouts are used to trace circles on cardboard which are in turn cut out. For each gear, two cardboard circles are cut out and glued together to create a rigid gear body. 
3. Gear teeth are made from the internal mesh found inside cardboard. Thin strips are cut out from cardboard and one external surface is removed to reveal the internal mesh structure. 
4. The gear teeth strips are hot glued on the outer edge of the cardboard gear cutouts. This is done for each gear. In this project, the quantities for each gear diameter are as follows: 4cm (x1), 5cm (x2), 6cm (x6), 7cm (x2), 8cm (x1). 
5. A housing for the gear box is constructed. The three shafts will attach to this housing. Ideally, ball bearings should be used to interface between the housing and the input/output shafts. 
6. After all gears have been mounted and glued, the shafts can be installed as seen below. The input shaft will have a motor attached externally as well. Spacing for gears is critical as it will determine which gears come into contact at each speed setting. 
7. The intermediate shaft has its gears mounted on a paper sleeve that slides along the stationary dowel underneath. (As such, the intermediate shaft is not mounted on bearings interfacing with the gear box housing). 
8. Once all three shafts are correctly installed, the final touches can be added. A user interface is added on the top that guides the dowel handle for the sliding transmission. An electronics setup is shown to the right which includes the motor, a switch, and two 9V batteries. 

Images from the fabrication process are shown below.