Chains and Gears 199
dharm
d:\N-Design\Des13-1.pm5
THEORY QUESTIONS
13.1 What is a gear and what is its function?
13.2 How are gears classified? Give their applications.
13.3 Define the following terms, as applicable to spur gearing:
(a) pitch circle diameter, (b) addendum, (c) dedendum,
(d) pitch point, and (e) pressure angle.
13.4 Why a gear drive is called a positive drive?
13.5 What are the commonly used tooth profiles and which one is the most extensively used?
13.6 Define an involute curve.
13.7 Which will run faster; the larger or smaller of the two meshing gears?
13.8 What is a rack and what is its purpose?
13.9 What is the difference between a rack and a pinion?13.10 Distinguish between:
(a) spur and helical gear,
(b) single helical gear and double helical gear,
(c) spur and bevel gear,
(d) gear and gearing,
(e) pinion and gear wheel, and
(f) worm and worm gear.DRAWING EXERCISES
13.1 A gear has 30 teeth of involute profile, pitch circle diameter of 180mm and pressure angle of 20°.
Draw the profile of four complete teeth for the gear. Also, draw the profile by approximate con-
struction method.
13.2 Sketch (a) sectional view from the front and (b) view from the side of a spur gear with a web.
13.3 Sketch the views of two gears, a pinion and gear in mesh. Indicate the required parameters.
13.4 Sketch a helical gearing, following the conventional representation.
13.5 Sketch a bevel gear, indicating the various terms and parameters.
13.6 Sketch (a) sectional view from the front and (b) view from the side of a bevel gearing. Indicate
the required parameters.
13.7 Through the necessary views, sketch a worm and worm gear separately; indicating the impor-
tant parameters.
13.8 Sketch the two views of a worm gearing; indicating the necessary parameters.