GATE Questions & Answers of Gears and Gear Trains

What is Gears and Gear Trains ?

Gears are machine elements that transmit motion from one shaft to another shaft by means of successively engaging teeth. The gear teeth act like small levers. When two or more gears are mesh together to transmit power from one shaft to another then such combination is called gear trains. A gear train may consist of spur, bevel or spiral gears depends on shafts position and required velocity ratio.

What is the Weightage of Gears and Gear Trains in GATE Exam?

Total 21 Questions have been asked from Gears and Gear Trains topic of Theory of Machines subject in previous GATE papers. Average marks 1.71.

An epicyclic gear train is shown in the figure below. The number of teeth on the gears A, B and D are 20, 30 and 20, respectively. Gear C has 80 teeth on the inner surface and 100 teeth on the outer surface. If the carrier arm AB is fixed and the sun gear A rotates at 300 rpm in the clockwise direction, then the rpm of D in the clockwise direction is A frictionless gear train is shown in the figure. The leftmost 12-teeth gear is given a torque of 100 N-m. The output torque from the 60-teeth gear on the right in N-m is In an epicyclic gear train, shown in the figure, the outer ring gear is fixed, while the sun gear rotates counterclockwise at 100 rpm. Let the number of teeth on the sun, planet and outer gears to be 50, 25, and 100, respectively. The ratio of magnitudes of angular velocity of the planet gear to the angular velocity of the carrier arm is ____________. A gear train shown in the figure consist of gears P, Q, R and S. Gear Q and gear R are mounted on the same shaft. All the gears are mounted on parallel shaft and the number of teeth of P, Q, R and S are 24, 45, 30 and 80, respectively. Gear P is rotating at 400 rpm. The speed (in rpm) of the gear S is_________ In the gear train shown, gear 3 is carried on arm 5. Gear 3 meshes with gear 2 and gear 4. The number of teeth on gear 2, 3, and 4 are 60, 20, and 100, respectively. If gear 2 is fixed and gear 4 rotates with an angular velocity of 100 rpm in the counterclockwise direction, the angular speed of arm 5 (in rpm) is A gear train is made up of five spur gears as shown in the figure. Gear 2 is driver and gear 6 is driven member. N2, N3, N4, N5 and N6 represent number of teeth on gears 2,3,4,5, and 6 respectively, The gear(s) which act(s) as idler(s) is/ are A pair of spur gears with module 5 mm and a center distance of 450 mm is used for a speed reduction of 5:1. The number of teeth on pinion is _______

A spur pinion of pitch diameter 50 mm rotates at 200 rad/s and transmits 3 kW power. The pressure angle of the tooth of the pinion is 20°. Assuming that only one pair of the teeth is in contact, the total force (in newton) exerted by a tooth of the pinion on the tooth on a mating gear is _______

Gear 2 rotates at 1200 rpm in counter clockwise direction and engages with Gear 3. Gear 3 and Gear 4 are mounted on the same shaft. Gear 5 engages with Gear 4. The numbers of teeth on Gears 2, 3, 4 and 5 are 20, 40, 15 and 30, respectively. The angular speed of Gear 5 is Which one of the following is used to convert a rotational motion into a translational motion?

It is desired to avoid interference in a pair of spur gears having a 20° pressure angle. With increase in pinion to gear speed ratio, the minimum number of teeth on the pinion

A compound gear train with gears P, Q, R and S has number of teeth 20, 40, 15 and 20, respectively. Gears Q and R are mounted on the same shaft as shown in the figure below. The diameter of the gear Q is twice that of the gear R. If the module of the gear R is 2 mm, the center distance in mm between gears P and S is The following are the data for two crossed helical gears used for speed reduction:
Gear I : Pitch circle diameter in the plane of rotation 80 mm and helix angle 30º
Gear II : Pitch circle diameter in the plane of rotation 120 mm and helix angle 22.5º
If the input speed is 1440 rpm, the output speed in rpm is

Tooth interference in an external involute spur gear pair can be reduced by

For the epicyclic gear arrangement shown in the figure, ω2 =100rad / s clockwise (CW) and ωarm =80rad / s counter clockwise (CCW). The angular velocity ω5 (in rad/s) An epicyclic gear train is shown schematically in the adjacent figure. The sun gear 2 on the input shaft is a 20 teeth external gear. The planet gear 3 is a 40 teeth external gear. The ring gear 5 is a 100 teeth internal gear. The ring gear 5 is fixed and the gear 2 is rotating at 60 rpm ccw (ccw=counterclockwise and cw=clockwise).

The arm 4 attached to the output shaft will rotate at

Match the type of gears with their most appropriate description.

 Type of gear Description P Helical 1 Axes non parallel and non intersection Q Spiral Bevel 2 Axes parallel and teeth are inclined to the axis R Hypoid 3 Axes are parallel and teeth are parallel to the axis S Rack and pinion 4 Axes are perpendicular and intersecting, and teeth are inclined to the axis 5 Axes are perpendicular and used for large speed reduction 6 Axes parallel and one of the gears has infinite radius

One tooth of a gear having 4 module and 32 teeth is shown in the figure. Assume that the gear tooth and the corresponding tooth space make equal intercepts on the pitch circumference. The dimensions ‘a’ and ‘b’, respectively, are closed to A gear set has a pinion with 20 teeth and a gear with 40 teeth. The pinion runs at 30 rev/s and transmits a power of 20 kW. The teeth are on the 20° full – depth system and have a module of 5 mm. The length of the line of action is 19 mm.

The center distance for the above gear set in mm is

A gear set has a pinion with 20 teeth and a gear with 40 teeth. The pinion runs at 30 rev/s and transmits a power of 20 kW. The teeth are on the 20° full – depth system and have a module of 5 mm. The length of the line of action is 19 mm.

The contact ratio of the contacting tooth is