Bevel gear ordinary gear is the shape of a cylinder. The pitch angle of a gear is the angle between the face of the pitch surface and the axis. The most familiar kinds of bevel gears have pitch angles of less than 90 degrees and therefore are cone-shaped. This type of bevel gear is called external because the gear teeth point outward. The pitch surfaces of meshed external bevel gears are coaxial with the gear shafts; the apexes of the two surfaces are at the point of intersection of the shaft axes. Bevel gears that have pitch angles of greater than ninety
Type 90 Kyū-maru to the left of the main gun. The profile of the Type 90 is similar to the German Leopard 2A4 and it uses modular ceramic and steel composite armor, common in contemporary tank designs. The adoption of modular composite armor design facilitates the upgrading and exchange of the armor, and its frontal turret armor is rated at 380mm of effective thickness against kinetic energy penetrators, while the upper frontal hull armor is rated at 320mm of effective thickness against kinetic penetrators. The Type 90 is smaller than most main battle tanks with a height of , a width of ,