This set of Automotive Engine Design Questions and Answers for Entrance exams focuses on “Valve Timing Technologies – Engine Bearings”.
1. What is the thickness in mm of the overlay which is provided on the bearings?
Explanation: The thickness of the overlay or the third layer of Babbit is used on top of the copper-lead and aluminum bearings. Due to overlay, which is 0.01-0.02 mm thick, such bearings are expensive.
2. How is one of the bearings made to prevent the crankshaft from moving to and fro in the endwise direction?
a) Magnetic bearing
b) Fluid bearing
d) Thrust bearing
Explanation: To prevent the crankshaft from moving to and fro in the endwise direction, one of the bearings is made a thrust bearing. It is provided with flanges on both sides, which fit accurately with the sides of the crank web on which it is installed.
3. Which of the following is provided to cushion the journal and to increase the life of the bearing?
a) Direction control valve
c) Position control valve
Explanation: A overlay or third layer of Babbit is used on top of the copper-lead and aluminum bearings. Due to the overlay, which is 0.01-0.02 mm thick, such bearings are expensive. However the overlay cushions the journal during the running-in period and thus increases the life of bearing as well as journal.
4. Which is the bearing material which is being used in the modern engine?
b) Cast iron
Explanation: The bearing material used in modern engines is aluminum with small quantities of tin and copper, aluminum bearings are used for high load and speed conditions. However, it is more expensive due to which they are sometimes used with cheaper materials.
5. Which of the following helps the engine bearing by supporting the operating loads with minimum friction?
a) Good fuel-air ratio for combustion
b) Vibration dampers
Explanation: The engine bearing has main requirements like the engine bearing should support the operating loads with minimum friction using lubricant. Whereas the fuel-air ratio, vibration-dampers, and clutch do not affect the engine bearings.
6. Which one of the following is not an engine bearing requirement?
a) Corrosion resistance
b) Long life
c) Should multiple the variation of the shafts
d) Should have score resistance
Explanation: The engine bearing requirements are: they should have a long life, the bearing should have score resistance that prevents the bearing material from seizing to the shaft, corrosion resistance. Whereas the bearing has to have the ability to flow slightly to match the small variations in the shaft and not to multiply the variations.
7. Which are the types of material used in Babbit type bearing material?
a) Lead with a small quantity of copper and antimony
b) Steal with a small quantity of zinc and tin
c) Zinc with a small quantity of lead and copper
d) Silver with a small quantity of brass and aluminum
Explanation: Babbit is made by either lead or tin-based and contains a small quantity of copper and antimony. It is the oldest bearing material for automobile engines and is still used in application where soft material shaft under the moderate loads and speeds is employed.
8. Which of the following material is usually used in the backing to provide support against the shaft load?
Explanation: A modern engine bearing consists of bearing proper and a backing. The.backing is usually of steel which provides support against the shaft load acting on the shaft. There are three types of bearing material they are Babbit,copper-lead, and aluminum.
9. Which of the following more when compared to others in a medium-duty sealed powder bearings?
d) Fatigue strength
Explanation: In a medium-duty sealed powder bearing copper alloy lining with steel back. Copper-based alloys are harder and have higher fatigue strength but less conformability, embeddability, and corrosion resistance.
10. What is the value of antimony present in a Babbit metal?
Explanation: The Babbit metal are either antimony-tin or antimony-lead alloys. They have a very good conformability, embeddability, and corrosion resistance but a low fatigue strength. It has 7.5% of antimony, 0.2% lead, 0.1% arsenic, 3.0% copper and tin remainder.
11. Why are the holes provided in a main bearing as shown below?
a) To look attractive
b) For lubrication
c) Release the pressure
d) Vibration damping
Explanation: The oil holes are drilled from the main bearing to the crankpins through crank webs to provide lubrication of bug end bearing. Main bearings are lubricated from oil galleries in the cylinder block.
12. What is the value of silicon and copper in an extra heavy-duty type sealed power bearing?
a) 11% silicon and 1% copper
b) 1% silicon and 11% copper
c) 5% silicon and 10% copper
d) 10% silicon and 5% copper
Explanation: The extra heavy-duty sealed power bearing is made up of tin flash plate, Babbit over plate, aluminum alloy lobbying, and steel back. This contains 11% silicon, 1% copper, and the remainder aluminum. These alloys do not suffer corrosion as it is copper-based alloy.
13. Which of the following when decreased reduces the bearing clearance?
a) Number of shims
b) Number of valves
c) Displacement of the piston
d) Number of spark plugs
Explanation: Several shims are present on each side of the bearing, within it and the cap are also provided in the cast type for adjustment of clearance. Taking out several shims leads to a reduction in the bearing clearance.
Sanfoundry Global Education & Learning Series – Automotive Engine Auxiliary Systems.
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