Cylindrical gear is a common type of gear

The gear has straight teeth and is parallel to the axis of the wheel. Cylindrical gear is a common type of gear. The advantages of spur gears are simple design, economical manufacture and maintenance, and no end thrust. They apply radial loads to the bearings. Gears are called slow gears. If noise is not a serious design problem, gears can be used at speed.

These gears are usually considered to be high speed gears. Compared with spur gears of similar size, the load of helical gears is less. The movement of helical gear is more stable and quiet than that of spur gear. Single helical gear applies radial load and thrust load on its bearing, so thrust bearing is needed. The helix angle of the gear and the gear should be the same in size but opposite in direction, that is, the right-hand pinion is meshed with the left-hand gear. The intersecting but coplanar shafts connected by gears are called bevel gears. This arrangement is called helical gear drive. Straight bevel gears can be used on shafts at any angle, but right angles are common. Bevel gears have tapered blanks. The tooth thickness and height of straight bevel gear are conical. A rack is a rack or rod, which can be considered as a sector gear with a radius of curvature. By meshing the rack with the pinion, the torque can be converted into linear force: the pinion rotates; The rack moves in a straight line. This kind of mechanism is used in the automobile to convert the rotation of the steering wheel into the left-right movement of the pull rod. The rack also has a theory of gear geometry, where, for example, it can be the profile of a gear set with interchangeable racks, from which the profile of a gear with a specific actual radius can be derived. The rack and pinion type is used for rack rail.