06-07-2011, 11:49 AM
hai,
This is venkat reddy
i would like to know more about Semi automatic transmission
please send me this topic.
06-07-2011, 11:49 AM
hai, This is venkat reddy i would like to know more about Semi automatic transmission please send me this topic.
10-10-2012, 11:03 AM
Semi-Automatic Transmission Semi-Automatic.docx (Size: 441.99 KB / Downloads: 65) Abstract A semi-automatic transmission (also known as automated transmission, self-changing transmission, clutchless manual transmission, automated manual transmission, flappy-paddle gearbox, or paddle-shift gearbox) is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press a clutch pedal at the same time as changing gears. It uses electronic sensors, pneumatics, processors and actuators to execute gear shifts on the command of the driver or by a computer. This removes the need for a clutch pedal which the driver otherwise needs to depress before making a gear change, since the clutch itself is actuated by electronic equipment which can synchronise the timing and torque required to make quick, smooth gear shifts. The system was designed by automobile manufacturers to provide a better driving experience through fast overtaking maneuvers on highways. Comparison to other automated transmissions The automatic transmission is fully automatic and one does not need to change gears at all and it happens at the discretion of the computer in the car whereas in the semi-automatic transmission one can up-shift or down-shift without pressing the clutch. The gear can be engaged in manual mode wherein one can move it up and down to change the gears or one could operate the paddle shifters, just behind the steering wheel to perform the same operation. Many modern automated transmissions can also operate in the same manner as a conventional type of automatic transmission by allowing the transmission's computer to automatically change gear if, for example, the driver were redlining the engine. The ability to shift gears manually, often via paddle shifters, can also be found on certain automatic transmissions (manumatics such as Tiptronic) and continuous variable transmissions (CVTs) (such as Lineartronic). Other applications Racing According to the Car Crazy episode "Le Mans Museum of the Automobile", the paddle shifter interface could be found as early as 1912. The system used an inner steering wheel to select a gear level and can be seen on the "Bollée Type F Torpédo" of 1912, on show at the "Musée Automobile de la Sarthe" at the Le Mans race circuit. In Formula One, the first attempt at clutch-less gear changing was in the early 1970s, with the system being tested by the Lotus team. However, it would be much later that attention was turned back to the concept. In 1989, John Barnard and Harvey Postlethwaite, then-Ferrari engineers and designers, created a automated gearbox for use in the Ferrari 640 single-seater. Despite serious problems in testing, the car won its first race at the hands of Nigel Mansell. By 1994, the automated transmission was dominant in terms of gearbox technology, and the last F1 car fitted with a manual gearbox raced in 1995. After concerns that the technology allowed software engineers to pre-program the cars to automatically change to the optimum gear according to the position on the track, without any driver intervention, a standardized software system was mandated, ensuring the gears would only change up or down when instructed to by the driver. Buttons on the steering wheel, which go directly to a certain gear—rather than sequentially—are still permitted. ATVs Honda released automated electric shift ATVs starting in model year 1998 with the TRX450FE aka Foreman 450ES ESP (Electric Shift Program). Shifting is accomplished by pressing either one of the gear selector arrows on the left handlebar control. The current selected gear is indicated by a digital display. The primary components of the shifting mechanisms were the same on both the manual and electric shift models, but the major difference was the deletion of the shift pedal and the addition of an internal electric shift servo which actuated the components (clutch assy, shift drum, etc.)in one motion instead of the traditional foot lever. In the event of a malfunction, a supplied override lever can be placed on a shaft protruding from the crankcase in the traditional spot where the pedal would have been. This electric shift technology was later applied to their complete line of ATVs. Comparison to other automated transmissions The automatic transmission is fully automatic and one does not need to change gears at all and it happens at the discretion of the computer in the car whereas in the semi-automatic transmission one can up-shift or down-shift without pressing the clutch. The gear can be engaged in manual mode wherein one can move it up and down to change the gears or one could operate the paddle shifters, just behind the steering wheel to perform the same operation. Many modern automated transmissions can also operate in the same manner as a conventional type of automatic transmission by allowing the transmission's computer to automatically change gear if, for example, the driver were redlining the engine. The ability to shift gears manually, often via paddle shifters, can also be found on certain automatic transmissions (manumatics such as Tiptronic) and continuous variable transmissions (CVTs) (such as Lineartronic). Despite superficial similarity to other automated transmissions, automated transmissions differ significantly in internal operation and driver's "feel" from manumatics and CVTs. A manumatic, like a standard automatic transmission, uses a torque converter instead of clutch to manage the link between the transmission and the engine, while a CVT uses a belt instead of a fixed number of gears. A semi-automatic transmission offers a more direct connection between the engine and wheels than a manumatic and is preferred in high performance driving applications, while a manumatic is often preferred for street use because its fluid coupling makes it easier for the transmission to consistently perform smooth shifts,[1] and CVTs are generally found in gasoline-electric hybrid engine applications. |
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