TYPES OF DRIVE-IN AUTOMOBILES
From engine-rear wheel drive In this type of layout, the engine is fitted in front of the vehicle and drive to the wheels is to the rear as. The clutch and gearbox are fined in front and the drive to the rear axle is given with the help of a propeller shaft. The following are the advantages and disadvantages of this type of layout:
Advantages-
- The weight of the vehicle is well balanced on all the wheels.
- It provides enough space for the luggage
- It provides enough space for steering the front wheels.
- The efficiency of a cooling system is improved, as the radiator is provided in the front and gets a natural draft of air due to the forward movement of the vehicle.
- The clutch and gearbox are easily accessible for inspection, repair, and adjustment.
Disadvantages-
- Under heavy acceleration, oversteer and fish-tailing can occur.
- On snow, ice, and sand, rear-wheel-drive vehicles lose traction.
- Increased weight due to the addition of a long propeller shaft.
Front engine-front drive In this type of layout, the engine is fitted in the front of the vehicle, and the drive is also given to the front wheels.
Advantages
- It provides low flat floor since there is no propeller shaft and differential at the back, resulting in a lower center of gravity.
- The complete power train i.e. engine, clutch, gearbox, and differential are assembled and installed as a unit, thereby the cost is reduced.
- The vehicle has more adhesion on the straight roads as well as curves, placed on the driving wheels.
- The passenger and luggage compartment is spacious.
Disadvantages:
- On a gradient as well as while accelerating, the weight of the vehicle shifts to the rear wheel which reduces road adhesion, and thus the tractive effort is also reduced.
- On slippery gradients, understeer develops which is not desirable.
Rear engine - rear-wheel-drive In this type of layout, the engine is fitted in the rear of the vehicle and the drive is also given to the rear wheels. It may be noted that in this type of system, though long propeller shaft is eliminated but fixing up of controls such as gear shift lever, oil, and fuel gauges, accelerator, linkages are very complicated. Further, natural draft air due to the forward motion of the vehicle to the radiator is missing in this system.
Advantages
- It provides a low flat floor since there is no propeller shaft and small exhaust pipe, resulting in a lower centre of gravity.
- When the braking is done, some part of the weight of the vehicle is transferred to the front wheels, which helps in the quick stopping of the vehicle as more load is placed at the rear wheels.
- The vehicle has more adhesion on the roads specially when climbing hills, as more weight is placed on the driving wheels.
Disadvantages
- On a gradient, the weight of the vehicle moves to the rear, thereby reducing the weight on the front wheel, which reduces road adhesion, and thus the tractive effort is also reduced.
- To control the engine, clutch, gearbox, and differential, long linkages are required and the repair becomes difficult.
Four-wheel drive (4WD) In this type of layout, there is a transfer case that divides the engine torque to all four wheels of a vehicle. Since all the four wheels are getting driven, the whole of the vehicle weight is available for traction, thus it is advantageous for driving on slippery or unpaved roads and there are less chances of being stuck in the mud, sand, snow, etc. This type of system is provided on off-road vehicles but in recent years, however, 4WD systems are becoming popular to be used in all kinds of passenger vehicles.
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