Such a tricky and hard-to-pronounce word for a simple Russian person, like sequential, is derived from the English sequence, which in translation means: sequence. And the English name sequential manual gearbox in Russian sounds like a sequential gearbox. This is a device on cars of a certain class, allowing only sequential gear shifts from first to high and vice versa, without jumping.
traditional box
On traditional gearboxes installed on most domestic cars, the neutral position of the gearshift lever is set in the middle. In order to move off, we depress the clutch and shift into first gear. In the future, with a set of speeds, their sequential switching is recommended.
However, nothing prevents us from starting immediately at the second speed, if the road condition is normal and the engine is designed for such an action. Trying to start the engine with a dead battery, we, pushing the car, can immediately turn on the third, and even the fourth, to make it easier. Nothing prevents this. Decreasing the speed to perform a maneuver, we, having slowed down, from the fourth gear go immediately to the second or to the first. Having mixed up, you can turn on the wrong speed on the go, which is far from harmless for a car.
Automatic transmission
To simplify driving, an automatic transmission was invented, which freed the driver from the need to select a driving mode on a particular section of the road. The machine itself switches, while the driver, working with one foot, either increases speed or slows down. Driving a car with automatic transmission requires less skill, and it is not for nothing that the permit to operate such a vehicle is now highlighted in a separate category. 
But work on improving the mechanical transmission did not stop. As a result, a sequential transmission appeared, which also does not provide for the presence of a clutch pedal, but works on different principles. And its main feature is strictly sequential switching of speeds.
Sequential principle
Sequential gear changes can be noted, for example, on motorcycles, where they are switched on by foot. The neutral position there is most often located between first and second gear. The same mechanics are used on tractors, on big trucks. Sequential switching has received the greatest distribution in the boxes of sports cars, where every millisecond is precious and speed reduction when switching is unacceptable. The use of hydraulics allows you to further accelerate this process and reduce it to a minimum.
The sequential mechanism is based on a conventional manual gearbox, somewhat complicated in the process of modernization. The main feature is that with its help it is possible to switch from a lower to an increased gear without reducing the speed of the car, which invariably occurs when a traditional gearbox is operating. 
Cam or sequential
It must be said that a cam gearbox is installed on a number of racing cars. Although if the cam transmission is also made sequential, the already very high speed of switching modes will be even higher. And this is already applied on Formula 1 cars.
Unlike the helical gears on a traditional car gearbox, the cam gears are spur gears and long. This makes it related to the transmission of a sequential box. And it is this feature that allows both systems to switch without slowing down. At the same time, the device of the box itself is simpler - there are no synchronizers, but instead of many small teeth on the gear and clutch, there are end projections. Those same cams that directly engage with the gap. 
Peculiarities
On cars with a sequential gearbox, the shift lever is located on the steering wheel. Alternatively, buttons can be installed on the steering wheel. The desired button is marked with the letter "S". Both automatic and manual switching is provided. In this case, the box can operate in three modes:
- Standard mechanical.
- Mechanical sports.
- With automatic switching without driver intervention.
The advantages of this car of the future are the following points:
- A car with a sequential gearbox, like with an automatic transmission, does not have a clutch pedal - this is good for novice drivers.
- This box provides a choice between automatic and manual switching.
- High gearshift speed, which is reflected in the efficiency of the engine.
The disadvantage so far is the low wear resistance of the box mechanism.
The gearbox of a car is one of the most progressive parts of a vehicle.
During the production of cars, fundamentally new gearshift systems with different mechanisms were developed. One such device is the sequential gearbox.
Sequential gearbox: what is it
The concept of "sequential" comes from the English word sequence which means "sequence". Gears in such a box are switched sequentially, from lower to higher, and vice versa. This switching principle is used in motorcycles where the control is by foot. Indeed, by controlling the gear shift with the foot, it is difficult to perform complex manipulations. Therefore, we chose a simple algorithm: moving the lever up corresponds to an upshift, down to a downshift.
Video - clearly shows how quickly the gearshift occurs on a sequential gearbox:
There are still some vehicles where sequential checkpoints are traditionally used, military equipment (self-propelled artillery vehicles, tanks). They have their own specificity. First, they are driven by unskilled drivers. Secondly, a quick upshift is carried out with minimal “dips” in power during the shift. The second quality (practical absence of failures in power and speed) determines the use of sequential transmission in high-speed sports cars.
Video - what does a sequential gearbox mean on a Peugeot 208 racing car:
The principle of operation of a sequential gearbox
The design of a sequential gearbox in appearance differs little from a traditional manual gearbox.
If you take a closer look at the gear mechanism, you can immediately notice that the teeth are located strictly perpendicular to the side surface of the gear.
This is necessary to ensure that they move in a straight line during switching.
On the one hand, spur gears have less friction than oblique gears due to the full correspondence of the surfaces. On the other hand, helical gears in a mechanical box are designed to increase the torque that the gear train can withstand. Therefore, gears of increased width are installed in many sequential boxes. This enhances the design of the teeth and their strength.
The design of the sequential gearbox makes it quite easy to organize automatic switching modes. There are the following sequential gearboxes:
- with a conventional mechanical gear shift system;
- with sports switching system;
- with automated switching system.
Hydraulics are used to increase the switching speed. With the help of hydraulic servomotors, the switching time is minimal. During the activation of the shift to another gear, the accumulator is filled, which helps to create pressure in the hydraulic system. The shift time is a tenth of a second. This decisive fact determines the use of sequential gearboxes in sports cars. Often the gearbox controls are placed in the steering column area, which further simplifies the control of the modes.
How is it different from robotic
Many motorists mistakenly believe that the sequential gearbox is a close relative of the robotic one. Their fundamental difference lies in the use of a hydraulic system in a sequential gearbox when shifting gears. The robotic box uses an electric drive for this. Also in robotic boxes, a different gear shifting mode is used.
Video - shifting gears on a sequential gearbox of a racing car:
Their advantages and disadvantages
The main advantages of such boxes:
- minimum time for switching speed;
- minimal power losses of spur gears;
- fuel economy;
- the ability to switch from manual to automatic mode;
- the ability to control switching from the steering column;
- application of the system without using the clutch pedal.
Disadvantages of sequential gearbox:
- sequential gear shifting sometimes confuses the driver in terms of extreme driving styles, necessary gear changes, for example, during engine start “from the pusher”;
- relatively high weight of the gearbox with a similar power;
- reduced service life associated with the technical complexity of the mechanisms;
- high maintenance and repair costs.
In which cars can you find a sequential gearbox
Of the most common passenger cars, an example is a 1996 BMW with an SMG box. The SMG1 and SMG2 systems were installed on the BMW third series with the S index. Since 2004, this transmission has been installed on the BMW E60 M5. Also, a sequential gearbox was installed on certain models of Toyota Corolla, Mercedes S-class, BMW X5.
The layout of the sequential gearbox and its elements is shown in the figure:
In the figure: 1 - sequential gearbox control unit, 4 and 5 - indicator and mode switch, 7 - 6-speed gearbox, 12 - hydraulic unit, 10 - hydraulic drive, 11 - clutch.
Features of installing a sequential gearbox on VAZ cars
Many motorists, as an upgrade to their VAZ, purchase sequential gearboxes with a cam mechanism. Their appearance is about the same.
As for a significant effect, one cannot count on this, since the dynamics of the car, judging by the reviews of the owners, increases slightly, although these boxes are called "sports". In addition, the weight of such boxes is usually higher than traditional ones. Wide massive gears with a perpendicular arrangement of teeth are used there to compensate for their low load capacity.
In addition, spur teeth increase the noise level of the gearbox. The real service life of a handicraft sequential gearbox is short. Such a gearbox can be installed if the car is supposed to participate in sports competitions, but not for everyday city driving.
conclusions
Summing up, it can be noted that the development and introduction into serial production of sequential gearboxes has made a certain technical progress in the development of the automotive industry. Such checkpoints have not received wide distribution due to the presence of numerous shortcomings.
Thickness gauges for car body paintwork and have different operating principles.
Thanks to the evolution of a classic manual gearbox, new types of transmission have appeared, which in one way or another make driving a car easier and more comfortable. Automatic transmission has become a huge breakthrough in this area. Every year, it continued to be modified and improved, enabling the driver not to think about changing gears. At the same time, the manual transmission was not going to lag behind: it was also transformed, forming new, more advanced variations.
The sequential gearbox was one such innovation. It is strikingly different from others and allows you to change gears only in a strictly established sequence: down to go one lower, up - one higher.
Sequential gearbox: how it works
This type of gearbox is based on a conventional mechanical transmission. Among the main differences, it is worth noting the implementation of switching due to the hydraulic mechanism, the absence of a clutch pedal (the system is controlled by an electronic unit) and the change of helical gears to spur gears. These design features provide a significant reduction in shift speed, which is extremely important for racing and sports cars.
Where is used
Such a gearbox has become widespread in racing competitions. This was done with the expectation that during high-speed driving (when the car is exposed to vibration and heavy loads) it will be easier for the rider to shift gears sequentially than to try to get into a certain one.
Also, the sequential gearbox has long been actively used on conventional production cars and has managed to gain great popularity. Among motorists, she received the name of the manual transmission mode.
Clutch
Despite the lack of a corresponding pedal, the sequential gearbox has a clutch controlled by a specially designed electronic unit. It receives a signal from a sensor that determines the force of pressure on the gas pedal, and includes the necessary gear.
The electronic unit sends a command to the checkpoint to special sensors. After receiving the command, they transmit a signal to the progressive block, which contains the speed data. This device is the last element responsible for changing the operation of the engine. It receives commands from various sensors, from the included air conditioning system and the force on the pedals. The speed limit is calculated and corrected based on this information.
Classification
The sequential gearbox is divided into a servo gearbox (with or without automatic) and a direct-acting gearbox, mainly common on motorcycles. The principle of operation of the latter is as follows: the transition to one upper gear is made by the corresponding movement of the lever. The reverse algorithm is used to transfer to the bottom. There is a shutdown between the second and first gears, the inclusion is carried out with the help of an incomplete retraction of the lever.
The gears on cars are controlled by a lever used as a switch, as well as a mode selector. It is possible to use "petals" or buttons located on the steering wheel itself. The duplicated principle (lever + pedal) is used on tractors.
Advantages
The strengths of the gearbox include the absence of the clutch pedal itself, which makes novice drivers feel much more comfortable. Another indisputable advantage is the increased shifting speed compared to an automatic transmission or a standard mechanical one (after all, in terms of speed, the cam box occupies a leading position).
Makes switching approximately 150 ms. Such a short time interval is achieved due to the presence of a hydraulically based servo and electronic control of the system. The sequential automatic transmission is a game-changer in motorsport. Also, the car gets better grip with the road surface, since vibration and shaking are practically absent. The driver does not have to press the gas pedal all the way down to reach the required number of revolutions before an upshift is made.
The next advantage is the ability to select the switching mode. It can be automatic or manual control. There are generally three modes:
- fully automated;
- sports mechanical;
- standard mechanical.
The automatic adaptive sequential transmission is characterized by the presence of buttons on the steering wheel itself, so that the driver can control the gears without distraction. Also, the fuel consumption of the car is significantly reduced due to a well-organized transmission.
Weak sides
In the design of the transmission lies the disadvantages of this type. Difficulties lie in the low wear resistance of the hydraulic mechanism, which is subject to rapid wear during high-speed driving, which is why it often fails. The owners of racing cars have to sort out the entire structure very often.
The sequential gearbox on the VAZ and other production cars does not experience heavy loads and goes much longer without repair. Nevertheless, you need to properly operate the mechanism, be able to feel the time of the necessary downshift or upshift in mechanical mode. Otherwise, any part of the transmission, for example, the hydraulic drive, may suffer, which will result in a costly and time-consuming repair.
Sequential gearbox(from English. sequence - sequence, eng. sequential manual gearbox ) - a gearbox that allows only their sequential switching. It differs from the classic type gearbox by the principle of operation of the gear shift mechanism. Sequential shifting is useful when the control is actuated by the foot (for example, on a motorcycle), when fast shifting is required (for example, on a sports car), or when there are a large number of gears that are difficult to select using the traditional way of moving the lever (on tractors, trucks). Usually switching is carried out by shifting the control from the neutral position.
The shift mechanism can be either direct acting, such as on motorcycles, or servo-driven (automated or non-automated).
On motorcycles, the following gearbox control scheme is adopted:
- moving the lever up - shifting to a gear up;
- moving the lever down - shifting to gear down;
- neutral (shift off) is usually located between first and second gears, and is not engaged by the full travel of the lever.
On cars, it is usually controlled by a lever that simultaneously acts as a mode selector and gear shift, but can be controlled by buttons located on the steering wheel. On tractors, the sequential gearbox control can be duplicated: a lever and a pedal.
The sequential mode is designated by the Latin letter "S".
The sequential gearbox is based on a conventional mechanical transmission, only slightly modernized and "complicated". The gearshift process takes place using hydraulics, this is the main difference between this box and a robotic one. Also, switching occurs sequentially, that is, without skipping speeds.
The use of hydraulics reduces the shift time of the sequential gearbox to 150 milliseconds. It also allows you to protect the box from "rough" handling.
Gearshift levers are usually located on the steering wheel. There is both automatic switching and manual switching. Usually there are three modes:
1) standard mechanical;
2) sports mechanical;
3) automatic gear shifting by a sequential gearbox without driver intervention.
For example, in models M 3 stamps bmw shift speed dropped to 80 milliseconds. This is achieved through the use of aerospace technology, technology used in the "Formula 1". Also, sequential boxes have many modes that make life easier for the driver. This is the uphill mode, the snow track and many others.
In conventional gearboxes, in the process of switching speeds, the drive rod is pulled up, turned, pressed, and the gear we need is "selected". In the sequential box, pressure is created in the hydraulic unit and the hydraulic accumulator is filled. Then, through the operation of the hydraulic system, the gear shifting process takes place.
For example, in sequential checkpoint. There are two ways to change gears: using the steering wheel paddles, or using the shift lever in the center console, which allows you to instantly change from one gear to another without reducing speed or engine power or resorting to the clutch. The Launch Control system, which uses the optimal rev range for automatic gear changes, ensures the fastest possible acceleration. There is no need to take your foot off the accelerator pedal. It is also permissible to start moving in second gear (for example, on ice).
The sequential gearbox is based on a conventional manual gearbox. Among the most important innovations is the use of two switches located on the steering wheel, in addition to the conventional selector lever. The driver can shift gears without taking his hands off the steering wheel. Gear shifting is strictly sequential - none can be missed. The sequential gearbox reduces the risk of sloppy shifting and gear overload.
Information from Wikipedia, bmw.ru, autoclub36.ru and cars-area.ru was used to compile the publication.
As we know, the evolution of "boxes" in cars led the world to the invention of an automatic transmission, but the engineering mind did not stand still, and the mechanical transmission was not "put away" either - the engineers modernized the gear shift mechanism and created a variant of the sequential gearbox. In it, the gears were switched only sequentially up or down.
Sequence - sequence
The principle of operation of this gearbox is simple as in conventional mechanics, but it differs from the usual transmission we are used to, with spur gears that are installed instead of helical gears, and the role of the clutch pedal is performed by a hydraulic mechanism. This mechanism allows you to reduce the time of gear changes, which is so important in motorsport. In addition to shifting speed, such a box allows you to clearly shift gears at a time when the car is subject to vibrations and the use of a familiar gearbox is difficult. Also, one of the features of the device of a sequential gearbox is that the primary and secondary shafts in such a transmission are type-setting, that is, it consists of several intermediate interconnected elements. This feature allows mechanics to quickly change gears on sports cars right during the race in order to find the optimal gear ratios for gears under current competition conditions. However, not only sports cars can boast of such a "box" - and on your "automatic" you can move the selector position to the side and get a sequential gearbox. You usually call it "manual" mode.
Such a transmission has 3 possible options for working in a car:
- conventional mechanical
- mechanical sports
- fully automatic
And how to live with it?
As we know, any gearbox can cause a lot of controversy, have allies and opponents. This did not bypass the sequential transmission. But let's go in order: if you decide on a car with such a transmission, you will be pleased with the lack of a clutch pedal and the speed of the “box”, in addition, like any “mechanics”, a sequential transmission will save you fuel compared to automatic transmission. The second undoubted plus is the ability to drive in several modes, which we described above. Complementing our range of pluses is shifting gears directly on the steering wheel, in the presence of petals.
However, as we all understand, there are no perfect mechanisms, so even such a seemingly perfect box has problems. Since there is no clutch, as such, the hydraulic switching mechanism suffers, because it wears out more than usual due to increased loads. Look at the competitions in motorsport, for example in drifting, where after almost a couple of races the mechanics are already ready to repair the gearbox. Stock cars, of course, let you enjoy the ride a little longer, because if you do not play sports driver on the road, your gearbox will live happily ever after, but if you decide to play race car, get ready for the fact that repairing such gearboxes is very and very expensive, and replacing with a new one is even more expensive.
Myths and legends
It seems that they tried to figure out the technical and financial parts, and now let's go through the stereotypes associated with such boxes:
- "Sequential is a robot." But no! Although the principles of operation of such transmissions are similar, however, the robotic transmission has electric servos, against hydraulic ones in sequential ones.
- "Sequential and automatic are inseparable."- again not guessed. If it wasn't for the ubiquity of sport modes on today's automatic transmissions, you wouldn't even know about the sequential gearbox. Therefore, in civilian versions, a mixture of options is possible, but I have not seen sports cars with automatic transmission.
- "Only for sports cars, only for cars, only with a cam gearbox."- no, of course, if you use them in pairs, your advantage will be cosmic, but on production cars such transmissions have been excellent for more than a decade.
Not scared away?
If the enumeration of all the pros and cons did not scare away the desire to take possession of this type of transmission, I can only say one thing. This is the most promising type of “mechanics” that is relevant for powerful cars, and if we also deal with such a box, refine it and improve it, we will be able to return to that ideal world in which cars with a mechanical transmission have a place in everyday use, and in most models from manufacturers.
