How Motorcycles Work
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Motorcycle Transmission
A simple transmission
A motorcycle engine can create an enormous amount of power, which must be delivered to the wheels of the vehicle in a controllable way. The motorcycle transmission delivers power to the rear wheel through a series of structures that include the gearset, theclutch and the drive system.
Gearset
A gearset is a set of gears that enable a rider to move from a complete stop to a cruising speed. Transmissions on motorcycles typically have four to six gears, although small bikes may have as few as two. The gears are engaged by shifting a lever, which moves shifting forks inside the transmission.
A gearset is a set of gears that enable a rider to move from a complete stop to a cruising speed. Transmissions on motorcycles typically have four to six gears, although small bikes may have as few as two. The gears are engaged by shifting a lever, which moves shifting forks inside the transmission.
Clutch
The job of a clutch is to engage and disengage power from the engine crankshaft to the transmission. Without the clutch, the only way to stop the wheels from turning would be to turn off the engine -- an impractical solution in any kind of motorized vehicle. The clutch is a series of spring-loaded plates that, when pressed together, connect the transmission to the crankshaft. When a rider wants to shift gears, he uses the clutch to disconnect the transmission from the crankshaft. Once the new gear is selected, he uses the clutch to reestablish the connection.
The job of a clutch is to engage and disengage power from the engine crankshaft to the transmission. Without the clutch, the only way to stop the wheels from turning would be to turn off the engine -- an impractical solution in any kind of motorized vehicle. The clutch is a series of spring-loaded plates that, when pressed together, connect the transmission to the crankshaft. When a rider wants to shift gears, he uses the clutch to disconnect the transmission from the crankshaft. Once the new gear is selected, he uses the clutch to reestablish the connection.
The belt drive on a Buell Lightning
Drive Systems
There are three basic ways to transmit engine power to the rear wheel of a motorcycle: chain, belt or shaft. Chain final-drive systems are by far the most common. In this system, a sprocket mounted to the output shaft (i.e., the shaft in the transmission) is connected to a sprocket attached to the rear wheel of the motorcycle by a metal chain. When the transmission turns the smaller front sprocket, power is transmitted along the chain to the larger rear sprocket, which then turns the rear wheel. This type of system must be lubricated and adjusted, and the chain stretches and the sprockets wear, requiring periodic replacements.
There are three basic ways to transmit engine power to the rear wheel of a motorcycle: chain, belt or shaft. Chain final-drive systems are by far the most common. In this system, a sprocket mounted to the output shaft (i.e., the shaft in the transmission) is connected to a sprocket attached to the rear wheel of the motorcycle by a metal chain. When the transmission turns the smaller front sprocket, power is transmitted along the chain to the larger rear sprocket, which then turns the rear wheel. This type of system must be lubricated and adjusted, and the chain stretches and the sprockets wear, requiring periodic replacements.
The Friction Drive The friction drive is another transmission found in some motorcycles. A friction drive is a type ofcontinuously variable transmission, or CVT, in which the variation in gear ratios comes about as a disc connected to the engine (the driving disc) rotates across the face of a second disc connected to the rear wheel (the driven disc). By varying the radius of the contact point between the two disc surfaces, different gears can be achieved. Continuously variable transmissions have a long history of use in motorized vehicles, with variable friction transmissions appearing in motorcycles in the early 1900s. |
Belt drives are an alternative to chain drives. Early motorcycles often used leather belts, which could be tensioned to give traction using a spring-loaded pulley and hand lever. Leather belts often slipped, especially in wet weather, so they were abandoned for other materials and designs. By the 1980s, advances in materials made belt final-drive systems viable again. Today's belts are made of cogged rubber and operate much the same way as metal chains. Unlike metal chains, they don't require lubrication or cleaning solvents.
Shaft final-drives are sometimes used. This system transmits power to the rear wheel via a drive shaft. Shaft drives are popular because they are convenient and don't require as much maintenance as chain-based systems. However, shaft drives are heavier and sometimes cause unwanted motion, called shaft jacking, in the rear of the motorcycle.
The other components that make a motorcycle a motorcycle are part of the chassis.
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How Sequential Gearboxes Work
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5-speed synchro box, ZF transaxle model 5DS-25-2 This gearbox has a custom-made sequential shifting mechanism that is pneumatically operated and computer controlled. See more images of transmissions.
Photo courtesy Derek Smith, Gruppe/5 Automotive
If you have read the HowStuffWorks article How Manual Transmissions Work, then you understand the inner workings of a typical manual transmission, and you know why manual transmissions use the standard "H" pattern in the shifter.
If you have ever ridden a motorcycle, you know that the manual transmission in a motorcycle is nothing like this. On a motorcycle, you shift gears by clicking a lever up or down with your toe. It is a much faster way to shift. This type of transmission is called a sequential gearbox or asequential manual transmission.
It turns out that most race cars use sequential gearboxes as well. A sequential gearbox gives the driver several important advantages that are very useful in a race car. We will discuss these advantages later in this article.
In this article, you will learn how a sequential manual transmission works and why this type of transmission is now appearing on so many high-performance vehicles.
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