Machine Dynamics Multiple Choice Questions on “Tangent Cam with Reciprocating Roller Follower”.
1. When the flanks of the cam are straight and tangential to the base circle and nose circle, then the cam is known as a ____________
a) Tangent cam
b) Reciprocating cam
c) Roller cam
d) Radial cam
Answer: a
Clarification: When the flanks of the cam are straight and tangential to the base circle and nose circle, then the cam is known as a Tangent cam.
2. Tangent cam with reciprocating follower is an example of cams with specified contours.
a) True
b) False
Answer: a
Clarification: Tangent cams are symmetric about the center line of the cam shaft and hence they fall into a category of cams with specified contours.
3. Tangent cams are symmetric about __________
a) Centre line of cam shaft
b) Tangent line of cam shaft
c) Radial line of cam shaft
d) Along the roller
Answer: a
Clarification: Tangent cams are symmetrical about the center line of the cam shaft. Not in all cases the roller is radial to the cam and has an offset, in these cases the cam is not symmetric about the roller.
4. What is the use of tangent cams?
a) To operate inlet and exhaust valves of I C engines.
b) To operate the inlet valve of I C engines
c) To operate the exhaust valve of I C engines
d) To operate the crankshaft of an IC engine
Answer: a
Clarification: Cams are used to change or transfer one type of motion to another type, in internal combustion engines, Tangent cams are used to operate inlet and exhaust valves.
5. In the given figure, the cam has contact with _______
a) Nose
b) Straight flank
c) Arm
d) Shaft
Answer: a
Clarification: The line connecting the smaller circle to the bigger circle is known as the Straight flank, in the figure given above, the follower circle has contact with the straight flank.
6. If θ is the angle turned by the cam from the beginning of the roller displacement, then minimum acceleration pf the follower occurs at what value of θ in degrees?
a) 0
b) 30
c) 45
d) 60
Answer: a
Clarification: Acceleration of the follower is given by the equation:
ω2(r1+r2)(2-cos2θ)/cos3θ
This will occur at θ=0 degrees.
7. From the given data, calculate the acceleration of follower in m/s2 at the beginning of the lift for a symmetrical tangent cam operating a roller follower.
Least radius of the cam is 30 mm; Roller radius is 17.5 mm. The angle of ascent is 75° and the total lift is 17.5 mm. The speed of the cam shaft is 600 r.p.m.
a) 187.6
b) 185.5
c) 183.2
d) 190.1
Answer: a
Clarification: At the beginning of the lift the angle turned by the cam from the beginning of the roller displacement is 0, hence acceleration is minimum which is given by the equation
ω2(r1+r2).
8. Maximum acceleration of the follower is independent of the angle theta.
a) True
b) False
Answer: b
Clarification: The maximum acceleration of the follower is given by the equation
ω2(r1+r2)(2-cos2θ)/cos3θ
hence it is not independent of theta.
9. In the given figure, the cam has contact with _______
a) Base circle
b) Nose
c) Straight flank
d) Shaft
Answer: b
Clarification: In the given figure the cam has 2 circular parts. The circular part with a bigger radius is called the base circle and the one with the smaller radius is called the nose. Hence the roller has contact with the nose.
10. If θ is the angle turned by the cam from the beginning of the roller displacement, how the velocity changes with the change in theta?
a) Increases with increase in theta
b) Decreases with increase in theta
c) Increases with negative change in theta
d) Independent of theta
Answer: a
Clarification: The velocity of the follower is given by the equation
V = ω(r1+r2)(sinθ/cos2θ)
Hence with increasing theta the velocity increases.