# Automotive Engine Components Design Questions and Answers – IC Engine – Big End Cap and Bolts

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

1. Which force is experienced by the connecting rod cap?
a) Gravity force
b) Magnetic force
c) Axial force
d) Inertia force

Explanation: The maximum force experienced by the connecting rod cap and bolts consists only of inertia force at the top dead Centre on the exhaust stroke. Hence, the inertia force is experienced by the connecting rod cap.

2. At which position of the piston, connecting rod cap experience inertia force?
a) Center

Explanation: The maximum force experienced by the connecting rod cap and bolts consists only of inertia force at the top dead center on the exhaust stroke. Hence, connecting rod cap experience inertia force at the top dead center.

3. Inertia force acting on the connecting rod cap is given by?
a) Pi=mrω2 r(θ+$$\frac{cos2\theta}{n_1})$$
b) Pi=mrω2 r(cosθ+$$\frac{sin2\theta}{n_1})$$
c) Pi=mrω2 r(cosθ+$$\frac{cos2\theta}{n_1})$$
d) Pi=mrω2 r(secθ+$$\frac{cos2\theta}{n_1})$$

Explanation: Pi=mrω2 r(cosθ+$$\frac{cos2\theta}{n_1})$$is the right answer where Pi is the inertia force, mr is the mass of reciprocating parts, ω is the angular velocity of the crank, r is the crank radius, n1 is the ratio of L/r and θ is the angle of inclination.

4. Calculate the mass of reciprocating parts when the mass of piston assembly is 0.6Kg and mass of the connecting rod is 0.4Kg?
a) 0.73Kg
b) 0.85Kg
c) 0.6Kg
d) 0.43Kg

Explanation: mr= mass of piston assembly+ $$\frac{1}{3}$$mass of connecting rod
= 0.6+$$\frac{1}{3}$$ (0.4)
= 0.73Kg

5. Find the crank radius when the length of the stroke is 80mm?
a) 10mm
b) 40mm
c) 30mm
d) 50mm

Explanation: Crank radius r=$$\frac{l}{2}$$ =$$\frac{80}{2}$$ =40mm
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6. Find the angular velocity of the crank rotating at 1200RPM?

Explanation: ω=$$\frac{2\times \pi\times N}{60}$$
=$$\frac{2\times \pi\times 1200}{60}$$

7. In the formula (Pi)max=mrω2r(1+$$\frac{1}{n_1})$$ what is mr?
a) Mass of reciprocating parts
b) Mass of all parts
c) Mass of cylinder
d) Mass of crankshaft

Explanation: In this formula, (Pi)max is the maximum inertia force, mr is the mass of reciprocating parts, ω is the angular velocity of the crank, r is the crank radius, n1 is the ratio of L/r.

8. Calculate the inertia force where the diameter of bolts is 10mm and σt=35N/mm2?
a) 5555.5N
b) 6107.8N
c) 6478.6N
d) 5497.7N

Explanation: (Pi)max=2($$\frac{\pi\times d_c^2}{4})$$σt
=2$$(\frac{\pi\times 10^2}{4})$$× 35
=5497.7N

9. Calculate the bending moment on the cap when (Pi)max=400N and span length is 80mm.
a) 3567.9N-mm
b) 4789N-mm
c) 5333.3N-mm
d) 6893.89N-mm

Explanation: Mb=$$\frac{(P_i)_{max}l}{6}$$
=$$\frac{400×800}{6}$$
=5333.3N-mm

10. Calculate the thickness of cap when σb=100N/mm2, Mb=90853.95N-mm, y=$$\frac{t_c}{2}$$ and I=6.25tc3?
a) 7.65mm
b) 8.53mm
c) 9.7mm
d) 6.23mm

Explanation: σb=$$\frac{M_b \times y}{I}$$
100=$$\frac{90853.95\times \frac{t}{2}}{6.25t^3}$$
tc=8.53mm

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