Many young drivers today will attempt their driving test in a manually operated vehicle. Yet this is fast becoming old-fashioned technology, and there are more automatic cars on UK roads than ever before. With this in mind, you may be looking at automatic cars for sale and may want to know a lot more about how these vehicles run. You'll find that there are many different automatic gearbox types on the road today and that some are increasingly sophisticated. With even more inventions set to debut in the years to come, UK motorists have even more choice.
The inner workings of a car fitted with a manual gearbox are relatively easy to understand. You depress the clutch pedal, which activates the release bearing, pulling the clutch plate away from the engine flywheel, and disconnecting the drive. You can then connect the most appropriate gears using the selector (or stick) and then release the pressure with your left foot. The plate will then be pushed back along the input shaft to restore the drive.
Torque Convertor Automatic
For generations, most automatic cars had a gearbox with a torque converter. This system replaced the manual clutch and was a revolutionary invention in its day.
Inside the converter, hydraulic fluid pumps under pressure from one point to another through several individual components. First, a centrifugal pump turns at very high speed while pressurised fluid flows through a small aperture. As the pump increases speed and more fluid enters the chamber, a vacuum forms to draw more fluid through the system.
The fluid will turn the blades of a separate turbine that links to the transmission shaft. Other components manage the fluid flow and vary its pressure as needed to select the most appropriate gear for the moment.
In essence, the faster the engine crankshaft turns, the more the pressure builds up within the torque converter casing. This action translates into a buildup of torque (or driving force) that varies according to the impeller's speed and fluid flow.
Dual Clutch Automatic
Over the years, there have been many variations on the theme, and sometimes an entirely different approach to the original process.
For example, many of today's vehicles feature a dual-clutch automatic transmission, a technique that's undoubtedly hybrid and mainly electronic. Again, there is no foot pedal, but there are two separate clutch mechanisms and each one links to the on-board computer. Here, the ECU monitors the engine's speed and the driving condition while adjusting the different clutches.
Each clutch is connected to a different gear and, as such, can select the most appropriate gear without actually disconnecting the transmission from the engine itself. This type of setup tends to be far more efficient than the old-fashioned torque converter. As the engine power flow is constant, and gear selection instantaneous, any vehicle with this system will feel smoother and record better mileage at the pump. In fact, the driver may not even notice that the car is changing gear at all when on the road.
Semi Automatic Cars
Some designers use on-board electronics to change the gears of a conventional manual gearbox. This type of approach is sometimes known as "semi automatic," as the ECU changes the gears without any input from the driver at all. SEAT and other manufacturers use this technology, and the driver can use a single lever that they simply push forward if they want to change gear.
Constantly Variable Transmissions
Toyota and other manufacturers like to fit constantly variable transmissions to their new vehicles. These products are very fuel-efficient and offer a smoother alternative to the conventional geared approach.
In this case, there are two separate pulleys inside the transmission, connected by a steel belt. The computer will adjust each pulley's position in relation to each other to vary the amount of torque passed between the engine and the wheels. If the driver selects a low gear, the main (or drive) pulley from the engine widens, and this will narrow the diameter of the driven pulley, connected to the drive shaft.
The belt that connects the two pulleys (or cones) must maintain the same tension at all times, so the transmission speed always relates to the engine's speed in any given driving condition. This approach does away altogether with the concept of different gears as there is, in effect, just a single gear with infinite variability.
All-Electric and Hybrid
An increasing number of vehicles on UK roads are electric and feature a completely different approach to transmission. These vehicles do not need a clutch at all, as there is never a need to disconnect the transmission from a constantly spinning engine.
Remember, a gearbox is simply an interface and a way to effectively harness the engine's power, whether the vehicle is stationary or not. The slower the vehicle's speed, the higher the revolutions to produce the right amount of energy and torque for the moment.
On the other hand, electric motors produce all of their torque instantaneously and thus only need a single-speed transmission. The engineers determine the rate of acceleration and maximum speed potential during the design process and strike a good balance as a compromise.
Nevertheless, certain manufacturers have decided to introduce a variable speed electric driveline. In this case, the vehicle may have more than one gear to give the driver options and a better acceleration rate in certain circumstances. These more options add more complexity, which will typically add to the overall cost. As electric cars tend to be far more expensive than their traditional counterparts, most manufacturers opt for a more straightforward approach.
In case you're wondering, the electric motor fitted to a typical hybrid has just one gear, while its internal combustion engine will typically use a constantly variable transmission.
Automatic Cars for Sale
When you're on the lookout for a conventionally powered car, bear in mind that those fitted with an automatic gearbox tend to cost somewhat more than a manual version. Automatics may not be as frugal at the pump, either.