# Automotive Engine Components Design Questions and Answers – IC Engine – Big and Small End Bearings

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This set of Automotive Engine Components Design Multiple Choice Questions & Answers (MCQs) focuses on “ IC Engine – Big and Small End Bearings”.

1. Which material is used in piston pin bearing?
a) Nickel-chromium
b) Silver
c) Iron
d) Phosphor bronze

Explanation: The piston pin bearing is usually a phosphor bronze of 3 mm thickness and it is an alloy of copper; it has good strength and corrosion resistance.

2. Using which process piston pin bearing is manufactured?
a) Forming
b) Forging
c) Casting
d) Machining

Explanation: It is a solid one-piece bush, made by casting and then finished by grinding and reaming operations. Grinding is done to reduce the friction and gives a shiny surface. Hence, casting is the right answer.

3. What is the l/d ratio for the crank pin?
a) 1 to 2.5
b) 1.5 to 1.9
c) 1.25 to 1.5
d) 1.67 to 1.9

Explanation: The allowable bearing pressure for the crankpin bush is usually taken from 5 to 10MPa, for this value the l/d ratio of crankpin is from 1.25 to 1.5.

4. In the formula Pc=dplp(pb)p what is dp?
a) Inner Diameter of the bush
b) Outer Diameter of the bush
c) Inner Diameter of the bore
d) Outer Diameter of the bore

Explanation: In the formula, Pc is the force acting on the piston pin, dpis the diameter of the piston pin, lp is the length of piston pin, (pb)p is the allowable bearing pressure.

5. Calculate the diameter of the piston pin when Pc=42951.46, lp=1.8dp, and (pb)p=14?
a) 35.88mm
b) 41.28mm
c) 45.89mm
d) 39.33mm

Explanation: By the formula Pc=dplp(pb)p
42951.46=dp×1.8dp×14
dp=41.28mm

6. In the formula Pc=dclc(pb)c, what is the unit of lc?
a) m
b) km
c) mm
d) N-mm

Explanation: In the formula, dc is the diameter of the piston pin, (pb)c is the allowable bearing pressure, lc is the length of piston pin, and is taken in mm.

7. Calculate the diameter of crankpin when Pc=42951.46, lc=1.1dp and (pb)c=8.5?
a) 67.78mm
b) 77.65mm
c) 57.23mm
d) 47.54mm

Explanation: By the formulaPc=dclc(pb)c
42951.46=dc×1.1dp×8.5
dc=67.78mm

8. In low-speed engines, L/r ratio varies from?
a) 2
b) 5 to 7
c) 3
d) 4 to 5

Explanation: In low-speed engines, connecting rods havea circular cross-section, this section can withstand the force when L/r ratio is 4 to 5.

9. Most connecting rods in high-speed engines have which cross-section?
a) T-section
b) Square
c) I-section
d) C- section

Explanation: I-sections are efficient in terms of material usage, it can bear high loads and can reduce the deflections. High-speed engines are with V-configuration and more than 4 cylinders. Hence, I-section is used.

10. Low-speed engines have which cross-section?
a) Rectangular-section
b) Circular-section
c) Square-section
d) Triangular-section 