Sequential Gearboxes

Running Head: SEQUENTIAL GEARBOXES

Abstract

This paper will discuss the technology of sequential gearboxes. Relatively new technology, the sequential gearbox has been applied mostly in ATV's, motorcycles, and the automobile racing industry. Recently this technology has begun to reach passenger cars. There are three main points of discussion; the workings of a manual transmission, how a sequential gearbox works and the advantages of them, and the applications of it today. The sequential gearbox is extremely revolutionary and is only used in high-end passenger cars, but maybe one day it will be a luxury the majority of the population will be able to experience.

Sequential Gearboxes

The sequential gearbox is a very interesting twist on a manual transmission. It dates back to the early 20th century; used mostly on motorcycles and other off road equipment during the World Wars (Italia, 1993). Since then this transmission has exploded into not only the racing world but also the passenger car world (Immell, 1994). Sequential gearboxes have numerous advantages over a standard manual transmission. To further understand the concept of a sequential gearbox one must know the basics of how a transmission works, and then can fully understand the advantages of a sequential gearbox.

Manual Transmission Basics

Cars or motorcycles need transmissions because of the physics of the gasoline engine. First of all any engine has a redline. A red line is the maximum rpm value above which the engine cannot go without blowing up and sending parts flying everywhere. Transmissions use gears and gear ratios to keep the engine running under its redline. Secondly, transmissions are needed in order to keep the engine in its maximum torque range. Without a transmission the engine would not be efficient at all, because it would never stay in the rpm range with the most power (Brain, n.d.). The whole philosophy behind shifting gears is to keep the engine in its best possible working range. When talking about transmissions there are essentially two different types of them; automatic and manual. A manual transmission simply means that the driver has to shift his or her own gears. An automatic transmission selects the appropriate gear itself based on road speed, engine speed and other technical factors. Sequential gearbox manual transmissions are an advanced type of transmission.

How Sequential Gearboxes Work

In a regular manual transmission there are three forks controlled by three rods that are engaged by the shift lever by the driver. The normal "H" pattern that the driver sees on top of the shifter enables him or her to move the shift lever between the control rods for the three forks and thus moving the rods back and forth. When all of these aspects are combined a successful shift is accomplished.

Transmissions on ATV's or motorcycles using sequential gearboxes have a set of gear selection forks that move collars, which engage the gears just like on regular manual transmissions. The gearshift lever is moved up and down by the foot and the transmission is moved from gear to gear. When the gearshift lever is moved by the foot, a ratcheting drum is rotated. This ratcheting drum has grooves cut into the side of it. The grooves on the ratcheting drum will direct the control rods when the drum is away from the transmission's gears. Moving the gear selector fork is the most common use of the grooves. With this in mind, whenever the lever is moved up or down, the drum is rotated one increment. The rotation of the drum allows for movement of the rods or forks as set by the grooves in the drum and the gears are then changed (Brain, n.d.). The gear shifting sequence can only be done in order; this means that no gears can be skipped, because of the rotation of the drum is the only thing that allows the gears to change. The shifting order must be correct whether shifting the gears from a higher gear to a lower or from a lower gear to a higher gear.

With a sequential shift approach in automobiles or racecars, the drum is rotated manually or by electronically solenoids, pneumatics, or hydraulics. A rotating cam located on the shift lever, which operates "dogs", accomplishes sequential shifts. These dogs, found on two counter-rotating shafts, carry the gears. The final drive mechanism is geared by one shaft and the other shaft is geared to the clutch. When the shift lever is moved, individual gears on one shaft intersect with matching gears on the other shaft. These two shafts are always meshed together, with neutral being the exception, and spin at a speed almost at the next higher or lower gear ratio (Brejcha, 1993). Therefore, engagement is easier and less intrusive.

There are distinct advantages to this type of transmission. These advantages are that it is much quicker when shifting. The shift is always consistent; it is the same motion for every gear, an up or down or back and forth. The location of the foot or hand is consistent, meaning that the shift lever is always in the same place, ready for the next shift. And, another advantage to a sequential gearbox is that there are no surprises. There is no chance of blowing up a transmission by mis-shifting; the transmission must be shifted in sequence (Brain, n.d.). This type of system virtually eliminates shifting mistakes. The last advantage to this transmission is that it takes up less space, which can be important in a vehicle such as a racecar where there is limited room.

Where Are They Today?

Sequential gearboxes for automobile applications first showed up in the racing industry. They got their start in the Formula One series. Formula One, being the leader in motor sport technology, needed a way to harness the massive amounts of horsepower produced by their engines, while still being able to shift quickly and efficiently. Today they use paddle shifters located behind the steering wheel. Every time the drive presses one of the paddles a shift change is electronically induced. The Indy Racing League, Champ Car Series, American Le Mans, and most other major racing leagues employ this technology.

Recently automobile manufacturers have begun to integrate some of their racing technology into their passenger cars. One of the first to do this was Ferrari. Ferrari introduced