Automatic vs. Manual Transmission

Automatic vs. manual transmission is a question relating to two kinds of engine control systems. A transmission is a complex system of gears and shafts that transmits and regulates the power of an engine. Transmissions are most commonly used in gasoline-powered vehicles. Two main types of transmissions are automatic and manual. Manual transmissions require the vehicle operator to change gears using a handle and pedal while driving. Automatic transmissions allow computerized sensors to determine and select the optimal gear without any input from the driver. Many drivers and manufacturers prefer automatic transmissions for their ease of use. However, manual transmissions may be easier to maintain, allow more human control of a vehicle, and add some benefits to vehicle performance.

Background

Gasoline-powered engines were invented in the late 1800s. The first models were fairly primitive, with few features, limited power, and little control. In the coming years, gasoline engines developed into highly sophisticated machines. They also became common in automobiles around the world. Modern engines offer tremendous strength and precise control. Much of the control is due to the complex structure of the modern engine.

The modern gasoline engine and its related components contain several main parts. Three of the most important ones are the engine itself, the clutch and flywheel, and the gearbox. The engine produces power and converts the power into motion of pistons, cylinders that move up and down rapidly. The reciprocating (up and down) motion of the pistons then converts into a rotary (turning) motion of a long bar called a crankshaft.

The crankshaft turns a notched wheel called a flywheel. In traditional designs, the flywheel is attached to the clutch. When a vehicle operator presses the clutch pedal, hydraulic pressure moves against the flywheel and causes the power from the engine to be disconnected from the rest of the vehicle. When the operator releases the clutch, the engine's power is reconnected.

With the clutch released and the flywheel turning, the engine's power moves along a rotating shaft into a new area known as the gearbox. The gearbox contains the gears and the various mechanisms used to shift between them, known collectively as the car's transmission system. Transmissions may be manual or automatic. In either case, they are necessary for safe and efficient vehicle operation.

Overview

The transmission system of a vehicle is necessary to transmit the power produced by the engine to the wheels to make the automobile move. The transmission does not just transmit the power directly, however. It allows the vehicle operator to regulate the amount of power that reaches the wheels, thus regulating the speed and performance of the vehicle. To do this, the transmission uses a series of different-sized gears (large notched rings).

The two main types of transmissions are manual and automatic. Manual transmissions allow the vehicle operator to switch between gears by hand (manually). Automatic transmissions are controlled by computerized sensors that select the best gear automatically, requiring no input from the human operator. Other than that, both systems operate along the same general principles.

The most crucial parts of automatic and manual transmissions are contained within the gearbox. The gearbox is a complex structure involving shafts (bars) and gears attached to the shafts. Manual transmissions have two shafts, a main shaft and a layshaft. Automatic transmissions have a single shaft with gears organized in a concentric pattern, often called a "planetary" arrangement.

The engine's power turns the shafts and the connected gears. Each gear represents a different level of power and performance for the vehicle. Engines may vary in their number of gears. Many engines, for instance, have six gears: first gear, second gear, third gear, fourth gear, fifth gear, and reverse.

The gears are sized differently to provide variations in speed and torque (rotational power). The first gear has the largest diameter, which makes it take longer to make a full rotation and thus provides a slower speed but higher torque. Each successive gear is smaller in diameter, leading to progressively faster speeds and lower torques. The reverse gear is the smallest gear, and it has a special secondary gear that causes it to turn in the opposite direction.

The entire gearbox assembly is connected to a selector mechanism. In manual transmission vehicles, the selector mechanism is usually a handled bar located under the dashboard that the vehicle operator moves by hand. The operator must first press on the clutch to disconnect the engine's power and then adjust the bar to the correct gear setting. Releasing the clutch will reconnect the engine's power at the chosen gear. Automatic transmission vehicles do not require a gear-selection bar because computer sensors handle the work of selecting gears.

When first gear is selected, a toothed ring called a "dog clutch" shifts to engage with the first gear on the shaft. The dog clutch teeth connect with the spinning gear and lock tight, transmitting that gear's power to the rest of the vehicle. Similarly, the operator or sensors may select other gears, causing the appropriate dog clutches to connect with the other gears of the shaft. Then, the regulated level of engine power is transferred along, ultimately reaching the vehicle's road wheels.

Although manual and automatic transmissions perform essentially the same task, most modern drivers prefer automatic transmissions. For that reason, automatic transmissions have become a standard in most new vehicles. The main reason for their popularity is their simplicity of use. Rather than having to constantly monitor speeds and make adjustments using the clutch and gear shifter, the vehicle operator can simply drive and allow computerized sensors to select the most efficient gear.

Some vehicle operators and manufacturers still prefer manual transmissions, however. Manual transmissions are more challenging to learn and use. Some drivers prefer to have this added control over their vehicle's operation, however. In addition, they prefer the relative simplicity of the manual system, which can be fixed with pure mechanics instead of relying on computer programs and sensors. Some studies have shown that manual transmissions may also slightly improve fuel economy and quicken acceleration.

Bibliography

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