# Automotive Engine Components Design Questions and Answers – IC Engine – Piston Skirt

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This set of Automotive Engine Components Design Multiple Choice Questions & Answers (MCQs) focuses on “IC Engine – Piston Skirt”.

1. Which portion of the piston is known as a skirt?
a) The portion above compression rings
b) The portion between compression and oil rings
c) The portion above the oil rings
d) The portion below oil rings

Explanation: Skirt is the cylindrical portion in the piston between the last oil scraper ring and the open end of the piston. Hence, Portion below oil rings is the correct answer.

2. Maximum side thrust is experienced during which stroke?
a) Intake stroke
b) Exhaust stroke
c) Expansion stroke
d) Suction stroke

Explanation: Side thrust is due to the sudden load on the piston and this is experienced during the downward moment of the piston i.e., during the expansion stroke.

3. Which of the mentioned below is the formula for calculating side thrust considering coefficient of friction?
a) Side thrust=PbD
b) Side thrust=PbDLs
c) Side thrust=μ$$(\frac{\pi D^2}{4})$$Pmax
d) Side thrust=$$(\frac{\pi D^2}{4})$$Pmax

Explanation: In the formula, we should concentrate on the Co-efficient of friction and it is present in the formula of Side thrust=μ$$(\frac{\pi D^2}{4})P$$Pmax.
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4. Which of the mentioned below is the formula for calculating side thrust considering stroke length?
a) Side thrust=PbDLs
b) Side thrust=PbD
c) Side thrust=μ$$(\frac{\pi D^2}{4})$$Pmax
d) Side thrust=μ$$(\frac{\pi D^2}{4})$$

Explanation: In the formula, we should concentrate on stroke length ls and the stroke length is present in the formula of Side thrust= PbDLs.

5. In the formula Side thrust=μ$$(\frac{\pi D^2}{4})$$Pmax what is the unit of Pmax?
a) N
b) N/mm2
c) N/m
d) N/mm

Explanation: In this formula of side thrust, µ is the coefficient of friction, D is the bore diameter and Pmax is the maximum bearing pressure and unit of pressure is always N/mm2.

6. In the formula Side thrust=PbDLs what is the unit of ls?
a) Cm
b) Km
c) mm
d) m

Explanation: In this formula for side thrust Pb is the allowable bearing pressure, D is the diameter whereas ls is the stroke length and it is always taken in mm.

7. Calculate the side thrust when μ=0.1, D=85mm and Pmax=4N/mm2?
a) 2269.8N/mm2
b) 100N/mm2
c) 3264N/mm2
d) 4563.4N/mm2

Explanation: Side thrust=μ$$(\frac{\pi D^2}{4})P_{max}$$
=0.1×$$(\frac{\pi\times 85^2}{4})\times 4$$
= 2269.8N/mm2

8. Calculate the stroke length when side thrust is 19634.95N/mm2, Pb=0.4N/mm2 and D=250mm?
a) 180.4mm
b) 143.4mm
c) 180.9mm
d) 196.3mm

Explanation: Side thrust= PbDLs
19634=0.4×250×Ls
Ls=196.3mm

9. Calculate the empirical relationship for the length of the skirt when D=80mm?
a) 20 to 40mm
b) 35 to 70mm
c) 52 to 64mm
d) 43 to 57mm

Explanation: ls= (0.65D) to (0.8D)
=0.65×80 to 0.8×80
= 52 to 64mm

10. Calculate the empirical relationship for the length of the piston when D=80mm?
a) 60 t0 90mm
b) 80 to 120mm
c) 70 to 100mm
d) 90 to 110mm

Explanation: L= D to 1.5D
= 80 to 1.5×80
= 80 to 120mm

Sanfoundry Global Education & Learning Series – Automotive Engine Components Design.

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