This set of Automotive Engine Components Design Multiple Choice Questions & Answers (MCQs) focuses on “IC Engine – Side Crankshaft at TDC Position”.

1. Which type of crankshaft is supported by two bearings?

a) Top crankshaft

b) Bottom crankshaft

c) Side crankshaft

d) Center crankshaft

View Answer

Explanation: The forces acting on the center crankshaft at the top dead centre position are two principal forces and to withstand this, the crankshaft is supported by two bearings.

2. In the design of side crankshaft at TDC position, the driven belt is assumed to be in which direction?

a) Vertical

b) Angled

c) Horizontal

d) Perpendicular

View Answer

Explanation: A crankshaft is subjected to bending and torsional moments due to the following two forces. Hence, In the design of centre crankshaft at the TDC position, the driven belt is assumed to be in a horizontal direction.

3. In the design of side crankshaft at TDC position, the crank alone is at which position?

a) BDC position

b) ODC position

c) TDC position

d) HDF position

View Answer

Explanation: A crankshaft is subjected to bending and torsional moments due to the following three forces. Hence, In the design of side crankshaft at the TDC position, the crank alone is at the TDC position.

4. In the design of side crankshaft at the TDC position, the engine is placed in which position?

a) Vertical

b) Horizontal

c) Parallel

d) Perpendicular

View Answer

Explanation: A crankshaft is subjected to bending and torsional moments due to the following two forces. Hence, In the design of side crankshaft at the TDC position, the engine is placed in a vertical position.

5. The reactions at the bearing 1 and 2 are due to which part of the engine?

a) Weight of camshaft

b) Weight of connecting rod

c) Weight of flywheel

d) Weight of the gears

View Answer

Explanation: The reactions at the bearing 1 and 2 are due to the weight of the flywheel(W) and the sum of their belt tensions(P

_{1}+P

_{2}) and reaction forces denoted by R

_{1}and R

_{2}.

6. Calculate the length of the bearing when the diameter of crankpin is 50mm?

a) 35 to 55mm

b) 87 to 90mm

c) 75 to 100mm

d) 91 to 109mm

View Answer

Explanation: l

_{1}=1.5d

_{c}to 2d

_{c}

=1.5×50 to 2×50

=75 to 100mm

7. In the formula P_{b}=\(\frac{R_1}{d_1l_1}\), what is P_{b}?

a) Bearing pressure

b) Torsional moment

c) Force

d) Shear force

View Answer

Explanation: In the formula P

_{b}=\(\frac{R_1}{d_1l_1}\), P

_{b}is the bearing pressure, R

_{1}is the reaction force at bearing 1, d

_{1}and l

_{1}are the diameter and length of bearing 1.

8. Calculate the bearing pressure when the reaction at 1 is 176700N and the length and diameter of crankpin are 120mm and 150mm.

a) 8.15N/mm^{2}

b) 7.89N/mm^{2}

c) 5.67N/mm^{2}

d) 9.81N/mm^{2}

View Answer

Explanation: P

_{b}=\(\frac{R_1}{d_1l_1}\)

P

_{b}=176700/(120×150)

=9.81N/mm

^{2}

9. Calculate the bending moment when load is 176700N, length of bearing is 265mm, thickness is 90mm and length of crank pin is 120mm?

a) 8.738×10^{6}N-mm

b) 89.3×10^{6}N-m

c) 55.21×10_{6}N-mm

d) 45.89×10^{6}N-m

View Answer

Explanation: M

_{b}=P

_{p}[0.75lc+t+0.5l

_{1}]

=176700[0.75×120+90+0.5×265]

=55.21×10

^{6}N-mm

10. In the formula M_{b}=P_{p}[0.75l_{c}+t+0.5l_{1}], what is l_{1}?

a) Length of shaft

b) Length of bearing

c) Length of connecting rod

d) Length of crank

View Answer

Explanation: In the formula M

_{b}=P

_{p}[0.75l

_{c}+t+0.5l

_{1}], M

_{b}is the bending moment, l

_{c}is the length of the crankpin, t is the thickness, l

_{1}is the length of the bearing 1.

11. Does the crank pin act as a which beam inside crankshaft?

a) Simply supported

b) Cantilever

c) Overhanging

d) Roller supported

View Answer

Explanation: The crankpin acts as a cantilever beam inside crankshaft and subjected to maximum bending moment on the crankshaft.

12. When the crank web is subjected to stresses, bending stress acts on which plane?

a) Horizontal

b) Both horizontal and vertical

c) Vertical

d) normal

View Answer

Explanation: When the crank web is subjected to stresses, bending stress acts on Both horizontal and vertical planes. This bending stress is equally divided on both the planes.

13. In the formula M_{t}=P_{t}×r, what is P_{t}?

a) Vertical component

b) Tangential component

c) Horizontal component

d) Normal component

View Answer

Explanation: In the formula M

_{t}=P

_{t}×r, P

_{t}is the tangential component, M

_{t}is the torsional moment and r is the crank radius. To avoida torsional moment, torsional rigidity should be good.

14. What is the thickness of the crankweb when the diameter of the crankpin is 50mm?

a) 12.5 to 77.5mm

b) 22.5 to 37.5mm

c) 28.7 to 48.5mm

d) 31.9 to 34.0mm

View Answer

Explanation: Thickness of the crank web is given by t=0.45d

_{c}to 0.75d

_{c}

t=0.45×50 to 0.75×50

=22.5 to 37.5mm.

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