Solved GATE Questions on Gear Trains
Question 1. In a cam design, the rise motion is given by a simple harmonic (SHM) 
where h is the total rise, 
is cam shaft angle, 
is the total angle of the rise interval. The jerk given by
(A) 
(B) 
(C) 
(D) 
GATE-ME-2008
Hint 1. (Ans. *)
Jerk is given by
Question 2. An epicyclic gear train is shown schematically in the adjacent figure
The sun gear2 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 rpn ccw (ccw=counter-clockwise and cw =clockwise).
Then arm attached to the output shaft will rotate at
(A) 10 rpm ccw
(B) 10 rpm cw
(C) 12 rpm cw
(D) 12 rpm ccw
GATE-ME-2009
Hint 2. (Ans A)
|
Condition |
Arm |
Gear 2 |
Gear 3 |
Gear 4 |
| 1. Arm fixed-gear 2 rotates with |
0 |
+1 |
|
|
| 2. Arm fixed gear 2 rotates with +x rotations |
0 |
+x |
-x |
-x |
| 3. Adding +y rotations |
y |
y+x |
y-x |
y-x |
Solving (1) and (2), we get
Question 3. For the epicyclic gear arrangement shown in the figure, 
=100 rad/s clockwise (cw) and 
=80 rad/s counter clockwise (ccw). The angular velocity 
(in rad/s) is
(A) 0
(B) 70 cw
(C) 140 ccw
(D) 140 cw
GATE-ME-2010
Hint 3. (Ans C)
| Arm | 2 | 3 | 4 | 5 | |
| 1. Give +x rotation CW to gear 2 | 0 | +x |  |
 |
 |
| 2. Give y rotation CW to arm | y | y | y | y | y |
| Total | y | y+x |  |
 |
 |
Speed of gear 5,
Question 4. Tooth interference in an external involute spur gear pair can be reduced by
(A) Decreasing centre distance between gear pair
(B) Decreasing module
(C) Decreasing pressure angle
(D) Increasing number of gear teeth
GATE-ME-2010
Hint 4. (Ans D)
Question 5. 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 30
Gear II: pitch circle diameter in the plane of rotation 120 mm and helix angle 22.5
If the input speed is 1440 rpm. The output speed in rpm is
(A) 1200
(B) 900
(C) 875
(D) 720
GATE-ME-2012
Hint 5. (Ans B)
Gear 1 : 
Gear 2 : 
Question 6. A compound gear train with gears P, Q, R and S has number of teeth 20, 40, 15 and 20 respectively. Gear 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 gear R. if the module of the gear R is 2 mm, the centre distance in mm between gears P and S is
(A) 40
(B) 80
(C) 120
(D) 160
GATE-ME-2013
Hint 6. (Ans B)
Module of meshing gear pair are equal.
Answer keys
1. (*) 2. (A) 3. (C) 4.(D) 5. (B) 6.(B)