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 AFV rear; the latter open outwards. In each side of the hull there are three firing ports with periscopes. On either side of the forward hull, a cluster of four 76 mm smoke grenade dischargers is mounted. The vehicle is fully amphibious, a folding trim board stowed at the front of the hull needs to be raised, and the vehicle can then propel itself in the water using its tracks. Standard equipment includes an NBC system, a Type 889 radio, and a Type 803 intercom system. Type 90 AFV The Type 90 is an armoured fighting vehicle produced by Chinese company