automatic gearbox

An automatic gearbox is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually. Most automatic transmissions have a defined set of gear ranges, often with a parking pawl feature that locks the output shaft of the transmission.

Similar but larger devices are also used for heavy-duty commercial and industrial vehicles and equipment. Some machines with limited speed ranges or fixed engine speeds, such as some forklifts and lawn mowers, only use a torque converter to provide a variable gearing of the engine to the wheels.

Besides automatics, there are also other types of automated transmissions such as continuous variable transmissions (CVTs) and semi-automatic transmissions, that free the driver from having to shift gears manually, by using the transmission's computer to change gear, if for example the driver were redlining the engine. Despite superficial similarity to other automated transmissions, automatic transmissions differ significantly in internal operation and driver's feel from semi-automatics and CVTs. An automatic uses a torque converter instead of clutch to manage the connection between the transmission gearing and the engine. In contrast, a CVT uses a belt or other torque transmission schema to allow an "infinite" number of gear ratios instead of a fixed number of gear ratios. A semi-automatic retains a clutch like a manual transmission, but controls the clutch through electrohydraulic means.

A conventional manual transmission is frequently the base equipment in a car, with the option being an automated transmission such as a conventional automatic, semi-automatic, or CVT. The ability to shift gears manually, often via paddle shifters, can also be found on certain automated transmissions (manumatics such as Tiptronic), semi-automatics (BMW SMG), and continuous variable transmissions (CVTs) (such as Lineartronic).



Automatic transmission modes

Conventionally, in order to select the transmission operating mode, the driver moves a selection lever located either on the steering column or on the floor (as with a manual on the floor, except that most automatic selectors on the floor don't move in the same type of pattern as a manual lever; most automatic levers only move vertically). In order to select modes, or to manually select specific gear ratios, the driver must push a button in (called the shift lock button) or pull the handle (only on column mounted shifters) out. Some vehicles position selector buttons for each mode on the cockpit instead, freeing up space on the central console. Vehicles conforming to US Government standards must have the modes ordered P-R-N-D-L (left to right, top to bottom, or clockwise). Prior to this, quadrant-selected automatic transmissions often used a P-N-D-L-R layout, or similar. Such a pattern led to a number of deaths and injuries owing to unintentional gear selection, as well as the danger of having a selector (when worn) jump into Reverse from Low gear during engine braking maneuvers.

Automatic transmissions have various modes depending on the model and make of the transmission. Some of the common modes include

Park (P)
This selection mechanically locks the output shaft of transmission, restricting the vehicle from moving in any direction. A parking pawl prevents the transmission from rotating, and therefore the vehicle from moving, although the vehicle's non-driven roadwheels may still rotate freely. For this reason, it is recommended to use the hand brake (or parking brake) because this actually locks (in most cases) the rear wheels and prevents them from moving. This also increases the life of the transmission and the park pin mechanism, because parking on an incline with the transmission in park without the parking brake engaged will cause undue stress on the parking pin. An efficiently-adjusted hand brake should also prevent the car from moving if a worn selector accidentally drops into reverse gear during early morning fast-idle engine warm-ups[citation needed]. It should be noted that locking the transmission output shaft does not positively lock the driving wheels. If one driving wheel slips while the transmission is in park, the other will roll freely as the slipping wheel rotates in the opposite direction. Only a (properly adjusted) parking brake can be relied upon to positively lock both of the parking-braked wheels. (This is not the case with certain 1950's Chrysler products that carried their parking brake on the transmission tailshaft, a defect compounded by the provision of a bumper jack). It is typical of front-wheel-drive vehicles for the parking brake to be on the rear (non-driving) wheels, so use of both the parking brake and the transmission park lock provides the greatest security against unintended movement on slopes. Unfortunately, the rear of most front-wheel-drive vehicles has only about half the weight on the rear wheel as is on the front wheels, greatly reducing the security provided by the parking brake as compared to either rear-wheel-drive vehicles with parking brake on the rear wheels (which generally have near half of the total vehicle weight on the rear wheels, except for empty pickup and open-bed trucks) or to front-wheel-drive vehicles with the parking brake on the front wheels, which generally have about two-thirds of the vehicle's weight (unloaded) on the front wheels.

A car should be allowed to come to a complete stop before setting the transmission into park to prevent damage. Usually, Park (P) is one of only two selections in which the car's engine can be started, the other being Neutral (N). In many modern cars and trucks, the driver must have the foot brake applied before the transmission can be taken out of park. The Park position is omitted on buses/coaches with automatic transmission (on which a parking pawl is not practical), which must be placed in neutral with the parking brakes set. Advice is given in some owner's manuals [example: 1997 Oldsmobile Cutlass Supreme owner's manual] that if the vehicle is parked on a steep slope using the park lock only, it may not be possible to release the park lock (move the selector lever out of "P"). Another vehicle may be required to push the stuck vehicle uphill slightly to remove the loading on the park lock pawl.

Most automobiles require P or N to be set on the selector lever before the internal combustion engine can be started. This is typically achieved via a normally open inhibitor switch, which is wired in series with the starter motor engagement circuit, and is only closed when P or N is selected, thus completing the circuit (when the key is turned to the start position)

Reverse (R)
This engages reverse gear within the transmission, giving the ability for the vehicle to drive backwards. In order for the driver to select reverse in modern transmissions, they must come to a complete stop, push the shift lock button in (or pull the shift lever forward in the case of a column shifter) and select reverse. Not coming to a complete stop can cause severe damage to the transmission[citation needed]. Many modern automatic transmissions have a safety mechanism in place, which does to some extent prevent (but does not completely avoid) inadvertently putting the car in reverse when the vehicle is moving forwards. This mechanism usually consists of a solenoid-controlled physical barrier on either side of the Reverse position, which is electronically engaged by a switch on the brake pedal. Therefore, the brake pedal needs to be depressed in order to allow the selection of reverse. Some electronic transmissions prevent or delay engagement of reverse gear altogether while the car is moving.

Some shifters with a shift button allow the driver to freely move the shifter from R to N or D, or simply moving the shifter to N or D without actually depressing the button. However, the driver cannot put back the shifter to R without depressing the shift button to prevent accidental shifting, especially at high speeds, which could damage the transmission.

Neutral/No gear (N)
This disengages all gear trains within the transmission, effectively disconnecting the transmission from the driven roadwheels, so the vehicle is able to move freely under its own weight and gain momentum without the motive force from the engine (engine braking). This is the only other selection in which the vehicle's engine can be started.

Drive (D)
This position allows the transmission to engage the full range of available forward gear trains, and therefore allows the vehicle to move forward and accelerate through its range of gears. The number of gear ratios a transmission has depends on the model, but they initially ranged from three (predominant before the 1990s), to four and five speeds (losing popularity to six-speed autos, though still favored by Chrysler and Honda/Acura)[citation needed]. Six-speed automatic transmissions are now probably the most common offering Toyota Camry V6 models, the Chevrolet Malibu LTZ, Corvette, GM trucks, Pontiac G8, Ford Falcon BF 2005-2007 and Falcon FG 2008 - current in Australia with 6 speed ZF, and most newer model Ford/Lincoln/Mercury vehicles). However, seven-speed autos are becoming available (found in Mercedes 7G gearbox), as are eight-speed autos in the newer models of Lexus and BMW cars.

Overdrive (D, OD, or a boxed [D])
This mode is used in some transmissions to allow early computer-controlled transmissions to engage the Automatic Overdrive. In these transmissions, Drive (D) locks the Automatic Overdrive off, but is identical otherwise. OD (Overdrive) in these cars is engaged under steady speeds or low acceleration at approximately 35–45 mph (56–72 km/h). Under hard acceleration or below 35–45 mph (56–72 km/h), the transmission will automatically downshift. Vehicles with this option should be driven in this mode unless circumstances require a lower gear.

Third (3)
This mode limits the transmission to the first three gear ratios, or sometimes locks the transmission in third gear. This can be used to climb or going down hill. Some vehicles will automatically shift up out of third gear in this mode if a certain RPM range is reached in order to prevent engine damage. This gear is also recommended while towing a caravan.

Second (2 or S)
This mode limits the transmission to the first two gear ratios, or locks the transmission in second gear on Ford, Kia, and Honda models. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time. Some vehicles will automatically shift up out of second gear in this mode if a certain RPM range is reached in order to prevent engine damage.

Although traditionally considered second gear, there are other names used. Chrysler models with a three-speed automatic since the late 1980s have called this gear 3 while using the traditional names for Drive and Low.

First (1 or L [Low])
This mode locks the transmission in first gear only. In older vehicles, it will not change to any other gear range. Some vehicles will automatically shift up out of first gear in this mode if a certain RPM range is reached in order to prevent engine damage. This, like second, can be used during the winter season, or for towing.

As well as the above modes there are also other modes, dependent on the manufacturer and model. Some examples include:

D5
In Hondas and Acuras equipped with five-speed automatic transmissions, this mode is used commonly for highway use (as stated in the manual), and uses all five forward gears.
D4
This mode is also found in Honda and Acura four- or five-speed automatics, and only uses the first four gear ratios. According to the manual, it is used for stop-and-go traffic, such as city driving.
D3 or 3
This mode is found in Honda, Acura, Volkswagen and Pontiac four-speed automatics and only uses the first three gear ratios. According to the manual, it is used for stop-and-go traffic, such as city driving.
S or Sport
This is commonly described as Sport mode. It operates in an identical manner as "D" mode, except that the upshifts change much higher up the engine's rev range. This has the effect on maximising all the available engine output, and therefore enhances the performance of the vehicle, particularly during acceleration. This mode will also downchange much higher up the rev range compared to "D" mode, maximising the effects of engine braking. This mode will have a detrimental effect on fuel economy. Hyundai has a Norm/Power switch next to the gearshift for this purpose on the Tiburon.

Some early GMs equipped with Tourqueflite transmsissons used (S) to indicate Second gear, being the same as the 2 position on a Chrysler, shifting between only first and second gears. This would have been recommended for use on steep grades, or slippery roads like dirt, or ice, and limited to speeds under 40 mph. (L) was used in some early GMs to indicate (L)ow gear, being the same as the 2 position on a Chrysler, locking the transmission into first gear. This would have been recommended for use on steep grades, or slippery roads like dirt, or ice, and limited to speeds under 15 mph.

+ −, and M
This is for the Manual mode selection of gears in certain automatics, such as Porsche's Tiptronic. The M feature can also be found in Chrysler and General Motors products such as the Dodge Magnum and Pontiac G6, as well as Toyota's Camry, Corolla, Fortuner, Previa and Innova. Mitsubishi and some Audi models (TT), meanwhile do not have the M, and instead have the + and -, which is separated from the rest of the shift modes; the same is true for some Peugeot products like Peugeot 206. Meanwhile, the driver can shift up and down at will by toggling the (console mounted) shift lever like a semi-automatic transmission. This mode may be engaged either through a selector/position or by actually changing the gears (e.g., tipping the gear-down paddles mounted near the driver's fingers on the steering wheel).
Winter (W)
In some Mercedes-Benz, BMW and General Motors Europe models, a winter mode can be engaged so that second gear is selected instead of first when pulling away from stationary, to reduce the likelihood of loss of traction due to wheelspin on snow or ice. On GM cars, this was D2 in the 1950s, and is Second Gear Start after 1990. On Ford, Kia, and Honda automatics, this feature can be accessed by moving the gear selector to 2 to start, then taking your foot off the accelerator while selecting D once the car is moving.
Brake (B)
A mode selectable on some Toyota models. In non-hybrid cars, this mode lets the engine do compression braking, also known as engine braking, typically when encountering a steep downhill. Instead of engaging the brakes, the engine in a non-hybrid car switches to a lower gear and slows down the spinning tires. The engine holds the car back, instead of the brakes slowing it down. GM called this "HR" ("hill retarder") and "GR" ("grade retarder") in the 1950s. For hybrid cars, this mode converts the electric motor into a generator for the battery. It is not the same as downshifting in a non-hybrid car, but it has the same effect in slowing the car without using the brakes.

Hybrid Synergy Drive system

Toyota uses its sophisticated Hybrid Synergy Drive system to power today’s Prius, a follow-on to the first-generation Toyota Hybrid System. Both automakers are now offering their second generation hybrid vehicles. In 2003, Honda introduced the five-passenger Honda Civic Hybrid, which offers a more powerful adaptation of the IMA system. A completely redesigned and more powerful Prius appeared as a 2004 model.

Both the Toyota and Honda hybrids are parallel configurations, with wheels driven by both their internal combustion engine and electric motor. In detail, however, they work quite differently.
Enginecrosssefront
The Honda IMA system’s electric motor/generator supplies additional power to the gasoline engine when needed for acceleration or when driving demands are greater, such as when climbing grades, thus the designation “motor assist.” The Honda gasoline engine always provides propulsion.



Things are reversed with Toyota’s Hybrid Synergy Drive, which finds the Prius starting out on battery electric power. The gasoline engine seamlessly starts up to provide additional power during acceleration, at higher speeds, or when driving up grades. This ability to run at times on battery power alone is an important distinction to some folks, since this means Toyota’s hybrids are actually zero emission vehicles during the time they’re electrically driven. Honda’s hybrids cannot do this.

The Prius uses a four-cylinder, 1.5-liter Atkinson cycle engine. The four-stroke Atkinson cycle, invented by James Atkinson in 1882, is different than the Otto cycle engine we’re used to driving in very distinct ways. Compared to the Otto cycle, where the intake valve is closed near bottom-dead-center, the Atkinson cycle does not close the intake valve at BDC, but leaves it open as the piston rises on the compression stroke. What this means is that some of the air/fuel charge is pushed back out and into the intake manifold and is used in other cylinders. This reduces the volume of the air/fuel mixture that’s compressed and combusted without severely restricting the throttle opening. Restricting throttle opening results in large pumping losses and greatly reduced efficiency. This method of reducing power output without incurring large pumping losses makes the Prius engine much more efficient than a conventional Otto cycle engine under most operating conditions. Effectively, the use of the Atkinson cycle allows the Prius engine to operate quite efficiently at relatively low power levels while still having sufficient power for climbing hills at freeway speeds.

The Prius uses the same basic 1.5 liter engine as the Toyota Echo, where the engine is rated at 108 horsepower at 6000 rpm. The Atkinson cycle allows the engine to be downsized to 76 horsepower at 4600 rpm while still being as efficient, or perhaps more so, than the Echo variant. Also, adding a supercharger to the Atkinson cycle results in the Miller cycle like that used in the Mazda Millenia.

Variable intake valve timing (VVT-I) reduces cylinder pressure to eliminate knocking, important because the engine has a 13:1 compression ratio. A high compression ratio, while good for performance and efficiency, can lead to pre-ignition (knocking), which can damage an engine if unchecked. The aluminum, dual overhead camshaft (DOHC) 16-valve engine produces 76 horsepower at 5000 rpm and 82 lbs-ft of torque at 4200 rpm. Because the engine speed is limited, it can use smaller and lighter components for improved fuel economy. The engine earns an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) rating, is a Super Ultra Low Emission Vehicle (SULEV), and has an EPA rating of 60 mpg city/51 mpg highway, for a combined estimated 55 mpg fuel economy rating.

Toyota’s HSD also takes special measures to address cold start emissions. Since combustion is not as efficient when an engine is cold and a catalytic converter must reach operating temperature before it can treat exhaust gases, cold starts result in greater emissions levels. The HSD system stores hot coolant in a three-liter vacuum bottle and dumps this into the engine during a cold start to help remedy this.

Anti-lock braking system

An anti-lock braking system (ABS) is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up (that is, ceasing rotation) and therefore avoiding skidding.

An ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, an ABS can significantly increase braking distance, although still improving vehicle control.[1]

Since initial widespread use in production cars, anti-lock braking systems have evolved considerably. Recent versions not only prevent wheel lock under braking, but also electronically control the front-to-rear brake bias. This function, depending on its specific capabilities and implementation, is known as electronic brakeforce distribution (EBD), traction control system, emergency brake assist, or electronic stability control (ESC).

Early systems

The ABS was first developed for aircraft use in 1929 by the French automobile and aircraft pioneer, Gabriel Voisin, as threshold braking on airplanes is nearly impossible. An early system was Dunlop's Maxaret system, which was introduced in the 1950s and is still in use on some aircraft models.[2] These systems use a flywheel and valve attached to a hydraulic line that feeds the brake cylinders. The flywheel is attached to a drum that runs at the same speed as the wheel. In normal braking, the drum and flywheel should spin at the same speed. However, if a wheel were to slow down, then the drum would do the same, leaving the flywheel spinning at a faster rate. This causes the valve to open, allowing a small amount of brake fluid to bypass the master cylinder into a local reservoir, lowering the pressure on the cylinder and releasing the brakes. The use of the drum and flywheel meant the valve only opened when the wheel was turning. In testing, a 30% improvement in braking performance was noted, because the pilots immediately applied full brakes instead of slowly increasing pressure in order to find the skid point. An additional benefit was the elimination of burned or burst tires.[3]

In 1958, a Royal Enfield Super Meteor motorcycle was used by the Road Research Laboratory to test the Maxaret anti-lock brake.[4] The experiments demonstrated that anti-lock brakes can be of great value to motorcycles, for which skidding is involved in a high proportion of accidents. Stopping distances were reduced in most of the tests compared with locked wheel braking, particularly on slippery surfaces, in which the improvement could be as much as 30 percent. Enfield's technical director at the time, Tony Wilson-Jones, saw little future in the system, however, and it was not put into production by the company.[4]

A fully mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF, and the experimental all wheel drive Ford Zodiac, but saw no further use; the system proved expensive and unreliable in automobile use.
[edit] Modern systems

Chrysler, together with the Bendix Corporation, introduced a computerized, three-channel, four-sensor all-wheel ABS called "Sure Brake" for its 1971 Imperial.[5] It was available for several years thereafter, functioned as intended, and proved reliable. In 1971, General Motors introduced the "Trackmaster" rear-wheel only ABS as an option on their Rear-wheel drive Cadillac models.[6][7] In the same year, Nissan offered an EAL (Electro Anti-lock System) as an option on the Nissan President, which became Japan's first electronic ABS.[8]

In 1975, Robert Bosch took over the European company Teldix and all patents registered by the joint-venture and used this acquisition to build the base of the ABS introduced on the market some years later.

Air Conditioners System

Air Conditioners Flow System

In order to understand, how the car air conditioning system operates, it is required to know various parts of this unit. First of all, the most important component which is present in this system is the compressor. The compressor is the central component which emits hoses of both high and low pressures. When these hoses come out, they go inside the condenser and finally to the evaporator. In this system, there are two types of valves like expansion and dryer valves, which are required for the proper functioning of this system. The function of expansion valves is to regulate the internal temperature of air, and it controls the refrigerant flow inside the system. There are certain anti-freezing agents as well like coolant or condensed gases, which pass through these valves.

The mechanism of a car air conditioning system is quite different from the conventional air conditioners. The car system instead of making the air cool, take out the heat, which is already found in the air. The Freon gas is used in the car air conditioning system which possesses a high temperature. When this gas passes through the compressor, the pressure channels mix it with the fresh air. The total gas mixture due to compression becomes liquid, and then it comes to the dryer. This chamber purifies the gas and sends to the evaporator through an expansion valve. The liquid gas absorbs the heat of the car which is then evaporated from here by the help of a blower or fan. This phenomenon repeats several times in order to make the environment cooler.

If you got certain problems in the car air conditioning system then you need to call a mechanic, since the fixing of this system is not a simple job. However; you can avoid the development of various problems in this system and hence can escape from big hassles. It is better to check the leakage of the car air conditioning system on a regular basis. Leakage takes out all the gas present inside the air conditioner and hence with the passage of time, the system becomes useless. It is also good to check the compressor regularly. It could be done by turning on the car followed by switching on the air conditioner. After that, lift up the bonnet and identify the compressor. If there is no movement in the compressor, it means there is some problem in the switching system. Sometimes refrigerant creates problems like the cooling does not happen in the opened system. If such types of problems are identified, call immediately to an electrician or a mechanic.

Four Wheel

There are almost as many different types of four-wheel-drive systems as there are four-wheel-drive vehicles. It seems that every manufacturer has several different schemes for providing power to all of the wheels. The language used by the different carmakers can sometimes be a little confusing, so before we get started explaining how they work, let's clear up some terminology:

* Four-wheel drive - Usually, when carmakers say that a car has four-wheel drive, they are referring to a part-time system. For reasons we'll explore later in this article, these systems are meant only for use in low-traction conditions, such as off-road or on snow or ice.
* All-wheel drive - These systems are sometimes called full-time four-wheel drive. All-wheel-drive systems are designed to function on all types of surfaces, both on- and off-road, and most of them cannot be switched off.

Part-time and full-time four-wheel-drive systems can be evaluated using the same criteria. The best system will send exactly the right amount of torque to each wheel, which is the maximum torque that won't cause that tire to slip.

In this article, we'll explain the fundamentals of four-wheel drive, starting with some background on traction, and look at the components that make up a four-wheel-drive system. Then we'll take a look at a couple of different systems, including the one found on the Hummer, manufactured for GM by AM General.

We need to know a little about torque, traction and wheel slip before we can understand the different four-wheel-drive systems found on cars.

Rear wheel

Rear Wheel Drive Cars
There are many benefits of rear wheel drive cars, but these come at a cost of driver safety. Experienced drivers do not face these problems though, and the number of people that prefer rear wheel drive cars is constantly rising today.
Rear Wheel Drive Cars
Ads by Google
Tour to Dubai? Guide from the official tourism portal of Dubai. Visit to know more www.definitelydubai.com
Hilton Hotels Hilton Hotels Official Site. Book Now for our Best Rates! www.Hilton.com
AxleTech International Rockwell, AxleTech On-Highway, Off-Highway, Axle & Brake Parts www.offhighwayplus.com
Most of the automobiles that are prevalent in the market today are manufactured with front wheel drives (FWD). This is a trend that has risen towards the end of the 20th century, as most cars of the 20th century were manufactured with rear wheel drives (RWD). There are plenty of reasons for this paradigm shift from FWD cars to rear wheel drive cars, but in the last couple of years, car manufacturers are shifting towards rear wheel drive cars once again. Read more about the history of cars.

The primary difference between FWD cars and rear wheel drive cars is the set of wheels that the engine controls. In RWD cars the engine is placed at the front end of the car, and the set of wheels that are powered by the engine are the rear wheels. This layout is commonly referred to as the front-engine rear-wheel drive layout, or the FR layout. Any motorcycle that you see on the road follows this layout, as it is the rear wheels that are powered by the engine. Read more about the various car parts.

Emergence of FWD Cars
There are plenty of reasons why rear wheel drive cars were replaced by front wheel drive cars, and the primary reason was that of car safety. Car manufacturers and drivers began to realize that the driving experience can be much safer if the car is fitted with a front wheel drive. The majority of the weight of the car is on the front wheels in the front wheel drive, and as a result of this the car tends to go straight, similar to an arrowhead that places the head at the front tip of the shaft. It still holds true that if a car skids or goes out of control, a front wheel drive enables the driver to regain control of the car easier and faster, thus avoiding car crashes. If a person does not know how to drive rear wheel drive cars properly, there's a high chance that he will be unable to regain control of the car if it slides, as at least half of the weight is on the rear side resulting in the car rotating. Learn about other car problems.

Despite these obvious safety concerns, most luxury cars, and even racing cars for that matter are endowed with rear wheel drives. The explanation for this is that since the weight of the car is almost equally distributed between the front and the back, there is greater balance while the car is in motion. This makes the car easier to handle, and lends a dynamism to its movement that cannot be experienced with front wheel drive cars. If the car needs to be stopped suddenly, rear wheel drive cars are far more superior to FWD cars as well. Read more on automobile safety ratings.

Disadvantages of Rear Wheel Drive Cars
Many car enthusiasts are firmly against RWD cars, and point out the following reasons for their inherent dislike of such vehicles.

* Since the engine is in the front, the transmission shaft that connects to the rear wheels have to travel under the entire length of the car's body. This increases the overall weight of the vehicle.
* Only someone who knows how to drive rear wheel drive cars can handle the vehicle effectively. Average drivers find it difficult to maneuver these cars.
* These cars are more expensive than FWD cars. This is due to the higher cost of assembly, owing to the presence of a long transmission tunnel that connects the engine to the rear wheels.
* On wet surfaces like snow, rain, gravel etc. these cars are tougher to navigate, as the car is being powered from behind, like a push, vis a vis a FWD car, where the engine acts like it is pulling a vehicle.
* Many people also complain about the lack of interior space and leg room in RWD car. This is again due to the presence of the transmission tunnel under the body of the car, running from the engine to the rear wheels.

Advantages of Rear Wheel Drive Cars
Along with these factors, there are other reasons why many people prefer to drive RWD cars.

* Since all the auto parts are spread out over a wide area, the repair and maintenance costs of RWD cars are relatively lower. Their repair does not require complicated disassembly and uses lesser specialized tools.
* Since the front wheels are concentrating on the steering, more power can be applied to the rear wheels and the vehicle on a whole under dry conditions. Since the force is lesser on the front wheels, more friction can be utilized towards steering.
* Under heavy and sudden braking, the car stops smoothly since the weight is evenly divided between the front and the rear of the vehicle.
* There is no presence of 'torque steer' in RWD cars, vis a vis FWD cars. The presence of this effect in FWD cars causes the car to shift slowly towards the right side at high speeds, owing to the difference in length of the shafts that connect the engine to the wheels.

How to Drive a Rear Wheel Drive Car in Snow
Driving rear wheel drive car in snow is a skill that can be acquired only through practice and caution. It is definitely more dangerous to drive a RWD car in snow than a FWD car, but for someone who is aware of how to drive rear wheel drive cars, this is no big feat. Just adhere to the following guidelines and you will do just alright.

Front-wheel

The vast majority of front-wheel drive vehicles today use a transversely mounted engine with "end-on" mounted transmission, driving the front wheels via driveshafts linked via constant velocity (CV) joints. This configuration was made popular by the 1967 Simca 1100,[2] and the 1969 Fiat 128.[citation needed] The 1959 Mini, while a pioneering transverse front-wheel drive vehicle[citation needed], used a substantially different arrangement with the transmission in the sump.

Volvo Cars has switched its entire lineup after the 900 series to front wheel drive. Swedish engineers at the company have said that transversely mounted engines allow for more crumple zone area in a head on collision. American auto manufacturers are now shifting larger models (such as the Chrysler 300 and most of the Cadillac lineup) back to rear-wheel drive.[3][4] There were relatively few rear-wheel drive cars marketed in North America by the early 1990s; Chrysler's car line-up was entirely front-wheel drive by 1990. GM followed suit in 1996 where its B-body line was phased out, where its sports cars (Camaro, Firebird, Corvette) were the only RWDs marketed; by the early 2000s, the Chevrolet Corvette was the only RWD car offered by Chevrolet until the introduction of the Sigma platform.
[edit] Records

Supercharger

Supercharger Basics

A basic engine with the addition of a supercharger.

An ordinary four-stroke engine dedicates one stroke to the process of air intake. There are three steps in this process:

1. The piston moves down.
2. This creates a vacuum.
3. Air at atmospheric pressure is sucked into the combustion chamber.

Once air is drawn into the engine, it must be combined with fuel to form the charge -- a packet of potential energy that can be turned into useful kinetic energy through a chemical reaction known as combustion. The spark plug initiates this chemical reaction by igniting the charge. As the fuel undergoes oxidation, a great deal of energy is released. The force of this explosion, concentrated above the cylinder head, drives the piston down and creates a reciprocating motion that is eventually transferred to the wheels.

Getting more fuel into the charge would make for a more powerful explosion. But you can't simply pump more fuel into the engine because an exact amount of oxygen is required to burn a given amount of fuel. This chemically correct mixture -- 14 parts air to one part fuel -- is essential for an engine to operate efficiently. The bottom line: To put in more fuel, you have to put in more air.

That's the job of the supercharger. Superchargers increase intake by compressing air above atmospheric pressure, without creating a vacuum. This forces more air into the engine, providing a "boost." With the additional air in the boost, more fuel can be added to the charge, and the power of the engine is increased. Supercharging adds an average of 46 percent more horsepower and 31 percent more torque. In high-altitude situations, where engine performance deteriorates because the air has low density and pressure, a supercharger delivers higher-pressure air to the engine so it can operate optimally.

Unlike turbochargers, which use the exhaust gases created by combustion to power the compressor, superchargers draw their power directly from the crankshaft. Most are driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. The drive gear, in turn, rotates the compressor gear. The rotor of the compressor can come in various designs, but its job is to draw air in, squeeze the air into a smaller space and discharge it into the intake manifold.

Turbo

DESIGN assumptions in
Designs related data before, some problems to be encountered will be emphasized.

Excessive Pressure
Turbo piston by the compressed air sent to the next stage more compressed by the piston to create an extreme pressure. This may heat the gas pressure (as warming occurs at high pressure thermodynamics), firing may take time before the fire. An event that causes a knock at the Buddha. Turbo pressure to reduce or prevent high-octane gasoline to use it.

Knock: Tapping; knock work with; unhealthy time of combustion-exhaust.

Turbo Time
Often, small-size turbo-equipped vehicles, acceleration does not respond instantly to commands sudden gas accumulation is seen. This slow development of the turbine can be caused by movement of the spinel. After a certain period began to run turbo (2000-2500 d / d), sudden gas start to run commands with a delay of 1-2 seconds and the car goes akselerasyona. Undesirable because of this delay is the weight of the turbine part, because a heavy need more power to turn the propeller. Yokedilemez delay completely, but parts made of lighter materials highly reduced.



Large - Small Turbocharger Comparison: Small volume applications turbo turbo lag is not open on time for the recording will be working and lower engine speeds. However, at high speed sufficient power production can not occur. In large volume produced more power at higher speeds, better acceleration values to obtain the delay time can not be prevented, but because in a larger size turbines and pumps are used. The method will be reviewed to eliminate it.

Turbine valve: This valve, the exhaust gas to evacuate more pressure adjusts the operation of the turbines. Turbines in a different way egzosta output is transferred to.
Bearings: bearings used herein, except in exceptional application is used as fat deposits. But they are special and lightweight materials are made of. Abrasion, corrosion, heat resistance is good.
Ceramics for Turbine Extended: Ceramic material is lighter than conventional metal materials has a structure. Abrasion resistance is also very high. Moreover, there are advantages to be used at high temperatures. Because ceramic is much higher than metal softening and melting temperature have. This material as a ceramic turbine makes use of important.
Dual turbocharger applications: In some cases, used for small turbo at low revs on acceleration as well as high speeds due to the insufficient large turbo is added.

RC Gear Box

Specifications
Type: Remote Control Car Gearbox (Gear box)
Dimensions: 40mm L x 30mm
Weight: 30g
Reduction Ratio: flexible
Torque: flexible
Rotational Speed: flexible

Material:
1. Housing: ABS
2. Gear: POM/ nylon
Applications: remote control cars
Target Markets: worldwide
Factory locations: Taiwan and Guangdong Province of China

Yeh Der has been to manufacture high-quality gears and gearboxes for industry since 1989. We provide both ODM & OEM services for gears and gearboxes (gear boxes), including designing, prototype making, manufacturing, assembling, testing, etc.

Our engineering has developed a broad range of gear and gearbox products, and on top of that, we have developed extremely flexible design and manufacturing capabilities in our nearly twenty years in business. This has allowed us to offer special features that help our customers simplify designs, improve performance and reduce costs.

With our strong engineering capabilities, we can develop precision gear and gearbox products to meet your most exacting requirements. We believe the key to reaching your performance goals is our working together.

Please contact us for more details.

Design details



A full range of transmissions especially designed for building it yourself. These gearboxes and transmissions are easy and cheap to manufacture, suitable for hobby model builders and amateur craftsmen. No precise or small tolerances. No special tools are needed, except for a small lathe and drill column. Off course some general knowledge of technical drawings and metal crafting is required.



All materials are available at hobby- and / or hardware stores. The housing is made out of stock aluminum bar 50x8mm, and the clutch parts are made out of stock round 40mm brass, epoxy ‘PCB’-, and steel sheet. All the parts like bearings, gears and shafts, are all standard catalog parts and can be purchased worldwide through internet at Sterling Instruments. A fully detailed parts list with complete ordering details comes with each set of plans.



Suitable for any rolling radio controlled vehicle like trucks, cars & tanks. The gearboxes can be powered by gasoline- or nitro engines, and are suitable for models up to 1/6 scale. Suitable for an estimated max input power of 1.5kW and a max input rpm of 15k ( for example 5cc nitro, 20cc 2-stroke, or 30 cc 4-stroke, gasoline ). Currently a range of 4 gearboxes is available; a tank transmission with 2 speeds forward 1 reverse, another tank gearbox-transmission with dual clutch and reversible track direction, a 2-speed clutch operated gearbox (configurable as a reverse-neutral-forward, or a low-neutral-high setup), and a 3 speed gearbox (configurable as a 1st-2nd-3rd gear, or a reverse-forward-overdrive setup). These gearboxes can be used modularly. By coupling them together, one creates a 4, 6 or 9 speed transmission. Or for example a 3-speed tank gearbox. (See pictures at bottom of page)

Gear box

# Gear box is an essential equipment in a gear assembly. Gear Box is also known as Gear head, Gear reducer and Speed reducer. The fundamental principle of a gearbox is to transmit the cause of mechanical rotation between two shafts. In this order, there is a structural support present in between the two shafts. Generally, gearboxes are kept inside the casings. This helps the gearboxes in their structural support, provides protection and ensures in doing safe functioning. Normally, the gearboxes are designed in reducing the speed, but sometimes, a gearbox may be designed for speed enhancing duties. The shafts inside the gearboxes are placed for the purpose of accepting and delivering the machinery rotation. This machinery rotation (torque) is achieved in the form of splines that should be suitable to connect or join to another unit. The capacity of thrusting outward of the shafts will have been limited from the casing. The mechanical rotation which is generated by the engine is consumed through the gearbox. This in turn, is being converted into a force at the road surface. To accelerate the vehicle, the force which is being applied can be calculated as follows:Spur Gear Box
Spur gearbox is an effective and durable mechanical equipment, which is used for the purpose of transmitting power and uniform and constant rotatory motion from one parallel shaft to the other shaft. Spur gearbox is also considered as a capable industrial tool that provides a continuous speed drive. This speed drive can be increased or decreased according to the requirement.

# Helical Gear Boxes
Helical gearboxes are quite alike the spur gearboxes in working. These gearboxes possess teeth that are fitted in a spiral format around the gear. The modern helical gearboxes are usually designed on a modular concept of construction and are available in different ratios. These gearboxes are fabricated to work absolutely without any noise, thus used in transmission operations.

# Hardened & Ground Gear Box
Hardened and ground gearboxes are considered one of the best types of gearboxes in the gears and gearbox manufacturing industry. They are widely used in many industrial applications in wind mills, cement industry, agro industry, fertilizer plants, aviation industry, and so. They are fabricated from industry standard raw materials like nickel, titanium, and stainless steel.

# Crane Duty Gear Box
These gearboxes are often used in heavy-duty applications. They are one of the advanced types of gearboxes, which give maximum thermal efficiency. These gearboxes facilitate the proper meshing of the gear teeth, which results in enhanced performance of the gear. The high efficiency is also ensured by its precision gearing and accurate bearings. It is often used in mining, automobiles, and construction industry.

RC Carburetors

A graphic look at a slide valve three needle R/C Nitro Engine Carburetor.

All r/c nitro engine carburetors are of the slide or rotary valve design.

This pictorial is of a slide valve r/c nitro engine carburetor. A large number of slide valve carburetors are of the three needle design.

A high speed, low speed and idle adjustment needle. There is some variance in this, some use only two needles.

While others use three needles, just that the manufacturer's use different terminology.

Now let us take a closer look at a r/c nitro engine carburetor. A graphic guide to all the parts that make up a r/c nitro engine carburetor.

Radio Control Nitro Engine Picture

Radio Control Nitro Engine Picture

Understanding your r/c nitro engine carburetor is very important.

Learning how to adjust your carburetor to critical in getting your r/c nitro engine to perform correctly.

Adjusting the high speed needle or screw either lean's or richen's your nitro fuel mixture entering the r/c nitro engine.

Adjusting this needle controls the temperature your engine is running at. Plus, it affects the overall performance of your r/c nitro engine.

Too some degree adjusting your high speed needle can change how your engine idles. It can be an art or science getting your r/c nitro engine carburetor adjusted properly.

Be patient and only do adjustments in small increments. A 1/16th to 1/4th of a turn.

I usually start at a 1/16th of a turn and see how that works and keep adding a 1/16th of a turn till I reach the tune that suits me.

So do take your time and keep notes on what adjustments you are making.

Radio Control Nitro Engine Picture



One other tuning factor that affects your r/c nitro engine is the carburetor restrictor.

Depending on which r/c nitro engine you have you will more than likely have two or three restrictors included with your engine.

The sizes of these restrictors will be from small, medium to large.

The actual millimeter size will vary depending on the size and manufacture of your r/c nitro engine carburetor.

The restrictor you use will depend on your driving style and how you have your engine tuned.

Just remember that changing the restrictor will require you to re-tune your r/c nitro engine carburetor.

Carburetor

A carburetor basically consists of an open pipe, a "Pengina" or "barrel" through which the air passes into the inlet manifold of the engine. The pipe is in the form of a venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a butterfly valve called the throttle valve — a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link, to the accelerator pedal on a car or the equivalent control on other vehicles or equipment.

Fuel is introduced into the air stream through small holes at the narrowest part of the venturi and at other places where pressure will be lowered when not running on full throttle. Fuel flow is adjusted by means of precisely-calibrated orifices, referred to as jets, in the fuel path.
[edit] Off-idle circuit

As the throttle is opened up slightly from the fully-closed position, the throttle plate uncovers additional fuel delivery holes behind the throttle plate where there is a low pressure area created by the throttle plate blocking air flow; these allow more fuel to flow as well as compensating for the reduced vacuum that occurs when the throttle is opened, thus smoothing the transition to metering fuel flow through the regular open throttle circuit.
[edit] Main open-throttle circuit

As the throttle is progressively opened, the manifold vacuum is lessened since there is less restriction on the airflow, reducing the flow through the idle and off-idle circuits. This is where the venturi shape of the carburetor throat comes into play, due to Bernoulli's principle (i.e., as the velocity increases, pressure falls). The venturi raises the air velocity, and this high speed and thus low pressure sucks fuel into the airstream through a nozzle or nozzles located in the center of the venturi. Sometimes one or more additional booster venturis are placed coaxially within the primary venturi to increase the effect.

As the throttle is closed, the airflow through the venturi drops until the lowered pressure is insufficient to maintain this fuel flow, and the idle circuit takes over again, as described above.

Bernoulli's principle, which is a function of the velocity of the fluid, is a dominant effect for large openings and large flow rates, but since fluid flow at small scales and low speeds (low Reynolds number) is dominated by viscosity, Bernoulli's principle is ineffective at idle or slow running and in the very small carburetors of the smallest model engines. Small model engines have flow restrictions ahead of the jets to reduce the pressure enough to suck the fuel into the air flow. Similarly the idle and slow running jets of large carburetors are placed after the throttle valve where the pressure is reduced partly by viscous drag, rather than by Bernoulli's principle. The most common rich mixture device for starting cold engines was the choke, which works on the same principle.