chassis desgin univ 2 marks

8/12/2019 Chassis Desgin Univ 2 Marks

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AT 2352 – AUTOMOTIVE CHASSIS COMPONENTS DESIGN

UNIVERSITY TWO MARK QUESTIONS

May/June 2012

1. Discuss the various loads acting on a chassis frame

2. What is an energy-absorbing frame

3. A steering gearbox has a gear ratio of 16:1 and an efficiency of 85%. Assume the driver to

exert a force of 60 N at the rim of the steering wheel 0.4m diameter, determine the torque at

the drop arm shaft.

4. What are the functions of front axle?

5. Why is cone clutch more effective that plate clutch

6. What are the types of clutch operating mechanisms used in automobile?

7. What are the possible arrangements to achieve 12 speeds from a gear box?

8. What are the difference between a constant mesh gear box and sliding mesh gear box?

9. State the formula used to compute critical speed of a propeller shaft. Why it is so important?

10. What are the types of stress experienced by semi-floating axle?

Nov/Dec 2012

1. What are the loading situations the chassis generally experiences?

2. What are the factors considered while designing a torsion bar?

3. What type of sections are provided at the middle and at the ends of the front axle?

4. What are the causes of steering geometry errors with up and down wheel movement?

5. When is the torque capacity of the clutch greatest?

6. List out the various components of a clutch.

7. Why is geometric progression in gear ratios?

8. When is maximum vehicle speed attained?

9. Why is the propeller shaft critical speed important/

10. What are the types of stresses experienced by semi-floating axle shafts?

May/June 2013

1. Differentiate between horizontal lozenging and lateral bending in a ladder chassis.

2. Mention the different configurations of laminated leaf spring suspensions.

3. Classify the various axle-hubs employed in automobiles.

4. What is the difference between hydrostatic and hydrodynamic lubrication? Also mention the

kind of lubrication employed in dead axles.

5. What are the factors to be considered while designing an automotive friction clutch?6. With an example give any two material properties for designing a friction clutch.

7. Mention the merits and limitations of gear drives.

8. What is meant by dynamic and static tooth loading in gear drives? How it is calculated?

9. Give the expression for calculating speed of propeller shaft.

10. A hatch back vehicle engine develops 30kW at 1450 rpm and its bottom gear ratio is 3:1. If a

propeller shaft of 38 mm outside diameter is to be used, determine the inside diameter of

mild steel tube to be used, assuming a safe shear stress of 56 x 103 kPa for the mild steel.

Nov/Dec 2011

1. Name the stresses that act on frame member.



2. Compare leaf spring with torsion bar.

3. The wheel base of a vehicle is 2m and the distance between the points of front axles is 1.3 m.

while taking a turn, the outside lock makes an angle of 20o. Determine the inside lock angle

for correct steering.

4. With neat diagram show the various stresses acting on front axle.

5. In a single plate dry clutch, the ratio of mean radius to the face width is 4 and the mean radius

of the friction lining is 110 mm. determine face width of the friction lining.

6. Axial force on each friction surface is 1400 N, mean radius of friction lining is 90 mm, the co-

efficient of friction is 0.3 and the number of pairs of friction surface is 4. Determine the torque

transmitted through this clutch.

7. What is the purpose of transmission system in an automobile/

8. Compare spur gear and helical gear transmission in automobile.

9. Sketch and name the parts of a propeller shaft in heavy load trucks.

10. Write down the types of rear axle housing.

April/May 2011

1. What are the loads and stresses the frame has to withstand?

2. Why are shackles used along with leaf springs?3. What are the types of stresses encountered by front axle?

4. Why do the front wheels have toe out on turns?

5. What are the major limiting the clutch capacity?

6. Why is the multi-plate clutch of smaller diameter preferred for high performance cars?

7. How are intermediate gears decided?

8. At what condition the vehicle attains maximum speed?

9. What are the limits of maximum and minimum diameter of the propeller shaft?

10. How is fully floating axle is different from other two constructions?

Answers

May/June 2013

1. Differentiate between horizontal lozenging and lateral bending in a ladder chassis.

Horizontal lozenging - the conditions like pot-holes, road joints, surface bumps and curbs

cause the chassis frame to distort to a parallelogram shape.

Lateral Bending – the chassis is exposed to lateral side force that may be due to the camber

of the road, side wind, centrifugal force while turning a corner, or collision with some object.

2. Mention the different configurations of laminated leaf spring suspensions.

Fully elliptic, three-quarter elliptic, half or semi elliptic, quarter elliptic, transverse mounted

semi elliptic and cantilever mounted semi elliptic.

3. Classify the various axle-hubs employed in automobiles.

Elliot type, reverse Elliot type, Lemoine type and reverse lemoine type

4. What is the difference between hydrostatic and hydrodynamic lubrication? Also mention

the kind of lubrication employed in dead axles.

Hydrodynamic lubrication is said to exist when the moving surfaces are separated by the

pressure of a continuous unbroken film or layer of lubrication. Hydrostatic lubrication is



essentially a form of hydrodynamic lubrication in which the metal surfaces are separated by a

complete film of oil, but instead of being self-generated, the separating pressure is supplied

by an external oil pump.

5. What are the factors to be considered while designing an automotive friction clutch?

a. Selection of proper type of clutch that is suitable for given application.

b. Selection of suitable material at the contacting surfaces.

c. Designing the clutch for sufficient torque capacity.

d. Engagement and disengagement should be without shock or jerk.

e. Provision for carrying away the heat generated at the rubbing surfaces

6. With an example give any two material properties for designing a friction clutch.

a. The two materials in contact must have a high coefficient of friction.

b. The materials in contact must resist wear effects, such as scoring, galling, and ablation

c. The materials should possess good thermal properties, high heat capacity, good thermal

conductivity, withstand high temperatures7. Mention the merits and limitations of gear drives.

Merits:

• No chain or belt to break

• High power transmission within compact space

Disadvantages:

• Noisy

• Cannot transmit power to longer distance.

8. What is meant by dynamic and static tooth loading in gear drives? How it is calculated?

Static gear loads are generated by statically loading the input shaft at the specified input torque, without

any motion being imparted to the gears. Dynamic load occurs when a pair of teeth is just coming into

mesh.

9. Give the expression for calculating critical speed of propeller shaft.

Critical speed Nc =1890000

* � (02 + 2

10. A hatch back vehicle engine develops 30kW at 1450 rpm and its bottom gear ratio is 3:1. If a

propeller shaft of 38 mm outside diameter is to be used, determine the inside diameter ofmild steel tube to be used, assuming a safe shear stress of 56 x 103 kPa for the mild steel.

Hint: Use formulas: P =2 60000 , kW

andTJ =

f sR

May/June 2012

1. Discuss the various loads acting on a chassis frame

Vertical bending



Longitudinal torsion

Lateral bending

Horizontal lozenging

2. What is an energy-absorbing frame

The modern vechile frames are made by constructing the front- and rear-end of the frame in

a manner so that it crumbles in a concertina manner during collision and absorb the main

shock of the impact.

3. A steering gearbox has a gear ratio of 16:1 and an efficiency of 85%. Assume the driver to

exert a force of 60 N at the rim of the steering wheel 0.4m diameter, determine the torque

at the drop arm shaft.

Refer notes on front axle and steering

4. What are the functions of front axle?

The front axle carries the weight of the front part of the automobile as well as facilitates

steering and absorbs shocks due to road surface variations.

5. Why is cone clutch more effective that plate clutch

Simple in construction

More area of frictional contact

6. What are the types of clutch operating mechanisms used in automobile?

Mechanical - Movement at the pedal pad is transferred through an operating mechanism, to the clutch

assembly on the rear of the flywheel.

Hydraulic - The pedal acts on a master cylinder, connected by a hydraulic pipe and flexible hose, to a

slave cylinder, mounted on the clutch housing.

7. What are the possible arrangements to achieve 12 speeds from a gear box?

Quick change gear box

8. What are the difference between a constant mesh gear box and sliding mesh gear box?

In sliding mesh gear box, the individual gear ratio is chosen by sliding the selected gearwheel

axially along the splined main output shaft, but in constant mesh gear box, the gears on the

lay shaft and the main shaft are always in a constant mesh, the gear ratio is selected by engage

the dog clutch.

9. State the formula used to compute critical speed of a propeller shaft. Why it is so important?

Critical speed Nc =1890000

* � (02 + 2

It is important to calculate the critical speed because, whirling may occur at certain critical

speed leading to failure of the material. So, the speed of operation of the propeller shaft should

be always lower than the critical speed.

10. What are the types of stress experienced by semi-floating axle?Driving torque as well as both vertical and horizontal loads. Vertical load produces shearing

force and bending moment. The horizontal force due to tilting of the vehicle, cornering

centrifugal force or side wind gives rise to both side thrust and a bending moment.



Nov/Dec 2012

1. What are the loading situations the chassis generally experiences?

Vertical bending

Longitudinal torsion

Lateral bending


2. What are the factors considered while designing a torsion bar?Torsion bar should be designed under maximum dynamic load (bump road) considerations

and the corresponding allowable stress.

3. What types of sections are provided at the middle and at the ends of the front axle?

At the center “ I” section is provided to withstand vertical bending and at the ends circular or

oval cross-section is provided to withstand torsional load.

4. What are the causes of steering geometry errors with up and down wheel movement?

Toe-in and toe-out and camber of the wheel

5. When is the torque capacity of the clutch greatest?

At minimum or zero slip, the torque capacity of the clutch is greatest.

6. List out the various components of a clutch.

Driving member – pressure plate assembly and fly wheel

Driven member – disc or plate assembly and the clutch shaft.

7. Why is geometric progression in gear ratios?

For heavy commercial vehicles, the gear ratios are usually arranged in geometric progression.The basis for this is to have the engine operating within the same speed range in each gear.

This would ensure that in each gear, the operating fuel economy is similar.

8. When is maximum vehicle speed attained?

The maximum vehicle speed is attained when the gear is set in top and the throttle is held

fully open.

9. Why is the propeller shaft critical speed important?

It is the speed at which the propeller shaft rotates violently lending to failure of the propeller

shaft. This should be avoided. The length of the propeller shaft governs the critical speed ofthe propeller shaft.

10. What are the types of stresses experienced by semi-floating axle shafts?

Driving torque as well as both vertical and horizontal loads. Vertical load produces shearing

force and bending moment. The horizontal force due to tilting of the vehicle, cornering

centrifugal force or side wind gives rise to both side thrust and a bending moment.

Nov/Dec 2011

1. Name the stresses that act on frame member.

Vertical bending stress

Longitudinal torsion shear stress



Lateral bending stress


2. Compare leaf spring with torsion bar.

3. The wheel base of a vehicle is 2m and the distance between the points of front axles is 1.3

m. while taking a turn, the outside lock makes an angle of 20o. Determine the inside lock

angle for correct steering.

Hint: use the formula cot φ – cot θ =

4. With neat diagram show the various stresses acting on front axle.

5. Axial force on each friction surface is 1400 N, mean radius of friction lining is 90 mm, the co-

efficient of friction is 0.3 and the number of pairs of friction surface is 4. Determine the

torque transmitted through this clutch.

Hint: Use the formula T = n µ W R to find the torque transmitted by the clutch

6. What is the purpose of transmission system in an automobile?

Transmission is the mechanism which is used to transfer the power developed by engine to

the wheels of an automobile. The transmission system of an automobile includes clutch, gear

box, propeller shaft axle and wheels, etc. The main function of the transmission is to provide

the necessary variation to the torque applied by the engine to the wheels. This is achieved by

changing the gearing ratio between the engine and the drive shaft.

7. Compare spur gear and helical gear transmission in automobile.In a spur gear the teeth are straight-cut and the edge of the teeth is parallel to the axis of

rotation. In a helical gear the teeth are cut at an angle and the edge of the teeth is non parallel

to the axis of rotation. Helical gears operate quietly compared to spur gears. Spur gear can be

used only in a transmission involving parallel orientation; the gears can be meshed correctly

only if they are perfectly parallel to each other. A helical gear on the other hand can be meshed

in parallel or cross orientation.

8. Sketch and name the parts of a propeller shaft in heavy load trucks.

9. Write down the types of rear axle housing.

Semi floating axle housing

Three-quarter floating axle housing

Full floating axle housing



10. In a single plate dry clutch, the ratio of mean radius to the face width is 4 and the mean

radius of the friction lining is 110 mm. determine face width of the friction lining.

Hint : use the formula R / b = 4.

chassis desgin univ 2 marks

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