1 What is machine design 2 Give a brief description of the t

1.      What is machine design?

2.      Give a brief description of the three basic gears?

3.      What is the purpose of gears ?

Solution

1) Machine Design is the process by which one form of energy is converted into useful mechanical form such that the output of the mechanism is in the useful form as per the need of the human beings.

2) Three basic types of gear are Spur, Helical and Bevel gear

Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially. Though the teeth are not straight-sided (but usually of special form to achieve a constant drive ratio, mainly involute but less commonly cycloidal), the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears mesh together correctly only if fitted to parallel shafts.No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds.

Helical or \"dry fixed\" gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle. Since the gear is curved, this angling makes the tooth shape a segment of a helix. Helical gears can be meshed in parallel or crossed orientations. It runs more smoothly and quietly.Helical gears are used in high speed applications, large power transmission, or where noise abatement is important

A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevel gears mesh, their imaginary vertices must occupy the same point. Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts. The angle between the shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and shaft axes at 90 degrees are called miter gears.

3)The main purpose of gears is to transmit power or torque or to change the rotational speed of an output shaft with respect to an input shaft. Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio.In Automobile gears are used to increase torque and in other application it is used to get the required RPM.