Figure 55 is an exploded line drawing of the gearbox from the food mixer in Figure 51. The gearbox has been pulled apart in a vertical direction and the parts are shown arranged on four levels. I shall now describe the contents of each level starting at the top level and working down to the bottom level. The top level depicts the top casing of the gear box. It is a fairly complex three-dimensional shape. The second level depicts the internal components of the gearbox. There are a total of eight gears arranged on four vertical shafts. Each shaft supports a pair of gears that are connected together and hence rotate at the same rate. One gear has a greater diameter and more teeth than the one its paired with. Two of the shafts are integral with the lower casing of the gear box and hence do not rotate. The gear pairs on these shafts are free to rotate whilst the shafts remain stationary. The gear pairs on the other shafts cause their shafts to rotate at the same rate as the gear pairs. One of these shafts will be rotated by a drive motor and the other will be used to drive a mixer tool. On this latter shaft, one of the gears is bevelled and this meshes with a ninth gear and shaft that rotates in a horizontal tubular hole in the top casing. The third level down depicts the lower casing of the gearbox. It is a fairly complex three-dimensional shape. It is thick enough to also form the sides of the gearbox. four circular cavities are visible to accommodate the gears and two of these cavities contain the integral shafts for their gears. The underneath of the lower casing is not entirely visible but it appears to have an additional circular protrusion to accommodate the parts at the next level down. The fourth level down depicts part of the mechanism that is required to cause the spinning tool to move in a circular path within the mixer bowl. There is a tool support that holds the tool drive shaft at a distance from the axis of rotation hence causing the tool to move in a circular path. A planet gear wheel is highlighted which is fixed to one end of the tool drive shaft. This planet gear would mesh with a fixed ring gear and this would cause the tool drive shaft to rotate as the shaft was being moved in a circular path. The ring gear is not visible but would be integral with the circular protrusion on the underneath of the lower casing of the gearbox.

 4.2 Manufacturing processes: making things