Which arrangement carries the drive to the rear wheels in a front engine car?
Answer: A
The propeller shaft runs from the gearbox to the final drive, with universal joints at each end to accommodate the angular movement as the axle rises and falls. A sliding spline accommodates the change in length. Long shafts are divided into two sections with a centre bearing to avoid whirling at high speed.
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Which problem does a long single piece propeller shaft suffer from?
Answer: B
A shaft has a critical speed at which it becomes dynamically unstable and bows outward, and that speed falls as the square of the length increases. Dividing the shaft into two supported sections raises the critical speed above the operating range. The problem is one of dynamics rather than of strength, since the shaft is amply strong in torsion. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.
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Which component supports the joint between two propeller shaft sections?
Answer: C
A rubber mounted centre bearing carries the shaft at the junction, supporting the weight while allowing the small movements that the suspension imposes. The rubber also isolates vibration from the body. Failure of the mounting is a common source of vibration and noise on high mileage rear wheel drive vehicles.
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Which joint type is used at the ends of a front wheel drive driveshaft?
Answer: D
A simple universal joint produces a cyclic speed variation when operating at an angle, which would be intolerable at the large steering angles a front wheel drive car requires. Constant velocity joints transmit uniform angular velocity regardless of angle. The outer joint is usually a Rzeppa ball type and the inner a tripod that also permits plunge. A single measurement chosen to respond to the one asymmetry beats several that respond to shared behaviour.
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Which fault does a worn constant velocity joint produce?
Answer: A
Wear in the outer joint produces a characteristic rhythmic clicking on full lock under power, usually caused by a split boot admitting dirt and losing grease. Rumbling suggests a wheel bearing and a braking vibration a warped disc. Recognising the noise and the condition that provokes it is the basis of a quick diagnosis.
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Which component protects a constant velocity joint?
Answer: B
The boot retains the special molybdenum grease and excludes water and grit, and a split boot leads rapidly to joint failure. Inspecting the boots is a standard service item for exactly this reason. Replacing a split boot promptly is far cheaper than replacing the joint once contamination has occurred, which is why the check is worth taking seriously at every routine service interval. Framing the question as which quantity the change acts upon makes the answer follow without calculation.
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Assertion (A): A ladder frame has poor torsional stiffness.
Reason (R): Its side rails are open channel sections that twist readily.
Select the correct answer from the options below.
Answer: C
An open section cannot sustain the circulating shear flow that resists torsion, so it twists far more readily than a closed box of the same weight. The reason therefore explains the assertion completely. Boxing the rails is the standard remedy and improves the torsional rigidity by an order of magnitude while adding relatively little weight.
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Assertion (A): A crumple zone reduces the energy absorbed in a collision.
Reason (R): A crumple zone extends the distance over which the vehicle decelerates.
Select the correct answer from the options below.
Answer: D
The reason is correct but the energy to be absorbed is fixed by the mass and the impact speed and cannot be reduced by the structure. What the crumple zone does is spread the absorption over a greater distance and therefore a longer time, reducing the peak force and deceleration. The assertion confuses energy with force, which is the commonest misunderstanding of crashworthiness.
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Statement I: Unitary construction is lighter than body on frame for the same stiffness.
Statement II: Body on frame construction is easier to build in many body variants.
In the light of the above statements, choose the correct answer.
Answer: A
Both statements are correct and together they explain why passenger cars use unitary construction while trucks retain a separate frame. The unitary body integrates structure and enclosure and avoids duplication, while the separate frame allows a common chassis to carry a pickup bed, a van body or a cab and chassis for a specialist conversion. Each construction suits a different set of commercial requirements.
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Consider the following statements about vehicle layouts.
1. Front wheel drive frees interior space.
2. Mid engine placement minimises the polar moment of inertia.
3. Rear engine placement gives poor traction under acceleration.
Which of the statements given above is or are correct?
Answer: B
The first two statements are correct, but a rear engine gives excellent traction under acceleration because the weight is already over the driven wheels and transfers further onto them. Its weakness is handling balance rather than traction. Each layout trades a different set of advantages, which is why several survive despite the dominance of front wheel drive. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.
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