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Hobby radio control

The word hobby; when you talk about radio-controlled cars to an uninformed person, they generally think of Nikko or Tyco cars, the sort you can see at the shopping mall. We like to think of our activity as a hobby, because it involves much more than just opening a box, dropping in a couple of AA batteries and hit the On button. No, this is about hobby-related skills, such as building and painting, and having a good set of tools and equipment and being proficient in their use. Just remember that a car may have up to 400 different parts! There is also a lot of science behind the driving of an r/c car!

Most of the radio-controlled cars are sold in a kit form, meaning that most of the times you will purchase an unassembled chassis with an unpainted body, without a motor or engine, no radio, batteries or charger. Some manufacturers sell RTR (Ready-to Run) cars, with even painted bodies, but this is not the case of competition kits.

There are almost as many kinds and sizes of cars as you can think of. There are electric cars, moved by small electric motors and fed by rechargeable batteries. They are quick, light, clean and almost completely silent. And there's the internal combustion engine-powered cars, nitro; these are powered by tiny engines, which are way more powerful (but not necessarily faster) than their electric counterparts, are noisier and have to run outside because of fumes.

R/C Cars also can be classified as On-Road or Off-Road, by the type of terrain they are supposed to be run on. On-Road being also on carpet or asphalt. Also, there is the subject of scale; a car is generally referred to as 1/10th, 1/8th and so on, depending of its size in relation to the real cars.

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All hobby-grade radio controlled cars require regular maintenance to ensure smooth and trouble-free operation. In comparison, cheaper "toy-grade" cars, found in discount and consumer electronics stores, are generally unserviceable. For those interested in mechanics, this maintenance provides an interesting adjunct to the hobby. Due to their modular construction, in the event that parts of a hobby-grade remote control car break or wear out, they can be replaced individually. The availability of many replacement and high-performance parts for hobby-grade model vehicles allows them to be extensively upgraded (sometimes, to the extent of having no original parts remaining whatsoever of the vehicle); in comparison, parts are generally impossible to find for toy-grade model cars, which are notoriously difficult to disassemble. In recognition of this distinction, Radio Shack released the popular XMODS and ZipZaps toy cars; these are mid-grade cars which can be tuned, modified, and repaired, although still to a lesser degree than professional hobby-grade vehicles.

In recent years, hobby-grade "ready to run" models have become available from every major manufacturer of remote control cars, attracting many hobbyists who would otherwise have purchased a pre-assembled toy car. Vehicles of this type need little or no final assembly and in some cases, the bodies are shipped painted and trimmed, requiring no further work from the owner before they can be used.

Principles of operation

Radio-controlled cars use a common set of components for their control and operation. All cars require a transmitter, which has the joysticks for control or a wheel, and a receiver which sits inside the car. The receiver changes the radio signal broadcast from the transmitter into suitable electrical control signals for the other components of the control system. Most radio systems utilize amplitude modulation for the radio signal and encode the joystick locations with pulse width modulation. Upgraded radio systems are available that use the more robust frequency modulation and pulse code modulation. The radio is wired up to either electronic speed controls or servomechanisms (shortened to "servo" in common usage) which perform actions such as throttle control, braking, steering, and on some cars, engaging either forward or reverse gears. Electronic speed controls and servos are commanded by the receiver through pulse width modulation; pulse duration sets either the amount of current that an electronic speed control allows to flow into the electric motor or sets the angle of the servo. On the models the servo is attached to at least the steering mechanism; rotation of the servo is mechanically changed into a force which steers the wheels on the model.

Electric models

Electrically powered models utilize either mechanical or electronic speed control units to adjust the amount of power delivered to the electric motor. The power delivered is proportional to the amount of throttle called for on the transmitter. Mechanical speed controllers use a network of resisters and switch between them by rotating a head with an electrode around a plate that has electrical contacts. Mechanical speed controllers are prone to being slow to react, waste energy in the form of heat from the resisters, and can become dirty and perform intermittently, and lack a dedicated braking ability. They are less expensive than high performance electronic speed controls and usually ship in low-end hobby-grade models. Electronic speed controllers use solid state components to either regulate electrical voltage or duty cycle, adjusting the power delivered to the electrical motor. In addition, some electronic speed controllers can use the electric motor as a magnetic brake, offering better control of the model than is possible with a mechanical speed control.

Electrically powered models usually stay cleaner during operation, are lighter in weight, and require less maintenance than fuel-powered models. After having run a few races with an electric car, the only dirt accumulated on the vehicle is usually from track dust. The light weight of electrically-powered cars allows them to accelerate rapidly. Another advantage that electric cars has against fuel-powered engines is that electric motors have a more even torque; in addition, they also have better throttle response. Electric batteries, however, take some time to charge; quick chargers can accomplish this in fifteen to thirty minutes while regular chargers take from one to four hours or even longer.

Routine maintenance usually consists of cleaning, inspecting the model car for damages, and replacing any parts that have been damaged during use.

Fuel models

Fuel powered models utilize a servo for throttle and braking control; rotation of the servo in one direction will cause the throttle on the carburetor to open, providing more air and fuel mixture to the internal combustion engine. Rotation of the servo in the other direction causes torque to be applied to a piece which causes friction with the braking material. The brake is located on the driveshaft and stops only two wheels on a two-wheel drive car and all four wheels on a four-wheel drive car.

Fuel engine sizes most often range between .12-.21 cubic inches. This is due to restrictions by the main sanctioning bodies for radio controlled racing. Many "outlaw" engines are manufactured larger than these, mainly intended for vehicles which will not be used in sanctioned races and therefore do not need to comply with these regulations. Engine size is related to the class of car; 1/10th scale on and off road vehicles usually are equipped with .12-.18 cubic inch engines, with 1/8th scale vehicles using .21-.26 cubic inch engines. While this is most common, there are exceptions, notably conversion kits that will allow a .21 size engine to be fitted to a 1/10th scale or a .46 size engine to be fitted to some 1/8th scales.

The overwhelming majority of fuel engines are 2-stroke piston engines, though some 4-stroke engines are commercially available for those who are mechanically inclined to attempt to fit them, with conversion kits available for a limited number of vehicles, however this has not gained much popularity for a few reasons. 4-stroke engines are generally more expensive than a comparable 2-stroke, mechanical complexity is increased making the need to regular maintenance more important, and 4-stroke engines must be larger to compensate for their lower power output for a given displacement. Still, there are benefits to a 4-stroke that has drawn some enthusiasts, namely a smaller and more quiet exhaust system and more consistant power with greater low-end torque.

Fuel-powered engines allow model cars to reach impressive speeds, with much higher top speeds than electric cars. Maximum power is generally achieved at medium to high speeds, and a slightly slower throttle response than electrically-powered vehicles is usually expected. This is because in an electric motor, the torque is instantaneous; in a nitro engine, as in a gasoline engine, it takes time for the engine to spool up and for the clutch to engage. Although this is slower than an electric motor, it is hardly noticeable because it all happens within milliseconds.

One disadvantage of fuel-powered engines is that tuning a fuel-powered vehicle requires some skill to maintain optimum performance, fuel economy, and to keep the engine from overheating, even in ready-to-run vehicles. Because of the higher performance and their ability to be driven for longer periods of time, mechanical wear to the vehicle is generally greater than in electrics. In addition, the increased speed and weight of fuel-powered vehicles generally leads to collisions causing greater damage to the collided vehicles, and some degree of safety concern needs to be considered when racing them.

Accessories

Both fuel-powered and electric models generally require the purchase of additional accessories. For electrical vehicles, battery packs and a suitable charger are needed to power the car. A soldering iron and supplies are often necessary to build high performance battery packs and install upgraded electronics. For fuel-powered vehicles, a glow plug heater and fuel are needed to start the engine, as well as 4 AA size batteries to power the onboard electronics. Hobby grade electric and fuel-powered vehicles almost always require 8 AA size batteries to power the transmitter.

Sanctioned racing

1/10-scale electric sedan on a carpet track

There are tracks and racing clubs around the world for enthusiasts to get together and race, and there are many levels of difficulty from novice all the way to professional, ensuring that there is a racing class regardless of skill or equipment level. R/C racing on a professional level is a serious motor sport, regardless of the size of the cars involved, with factory-backed drivers racing for cash prizes all over the world.

Some commonly raced classes and the types of models that race them are:

1/12 Electric Onroad - Rear wheel Drive Cam Am-bodied cars, Touring cars, oval racers
1/10 Electric Onroad - Touring cars, Can Am-bodied cars, Formula One/Indy cars, oval racers
1/10 Electric Offroad - 2WD trucks, 2WD buggies, 4WD trucks, 4WD buggies, dirt track oval racers
1/10 Nitro Onroad - Touring cars, Can Am-bodied cars, oval racers
1/10 Nitro Offroad - 2WD trucks, 2WD buggies, 4WD trucks, 4WD buggies, dirt track oval racers
1/8 Nitro Onroad - Touring cars, Can Am-bodied cars
1/8 Nitro Offroad - 4WD buggies, 4WD trucks

It should be noted that the fractional number used throughout this article refers to the model's scale in proportion to its full-sized counterpart. Therefore, a 1/10-scale car is one-tenth the size of a real car, though most purpose-built racing models are not built to true scale.

History

The beginnings of model racing

Small, nitromethane-powered engines originally entered the market in the 1940s. At the time, there was insufficient technology to control an engine-powered model car other than on a tether. "Tether cars", or "spin dizzies", were capable of speeds upwards of 70 mph (113 km/h), but merely ran in a circle from the tether. In the late 1960s, the first miniaturized solid state radio control systems became available, which allowed a model car to have servo-controlled steering, throttle, and brake functionality that could be remotely controlled from a radio control transmitter unit. This allowed model cars to be able to run a racetrack, with the ability for precise control in a similar manner as with a full-sized vehicle.

First commercial products

In 1976, the Japanese firm Tamiya, who were renowned for their intricately detailed plastic model kits, released a series of elegant but somewhat mechanically crude car models that were sold as "suitable for radio control". Although rather expensive to purchase, the kits and radio systems sold rapidly; Tamiya eventually turned their attention away from scale detail of vehicles and towards the development of more purpose-built remote control model cars. Featuring working suspensions, more powerful motors, textured off-road rubber tires and often topped with stylized "dune buggy" bodies, these models were durable, easy to assemble, capable of being modified, and simple to repair. These models can be credited with launching a boom in the popularity of radio controlled model cars in the early to mid 1980s, and they provided the basis for today's radio controlled car market.

A British firm, Schumacher Racing, was the first to develop a ball differential in 1980, which allowed nearly infinite tuning for various track conditions. At the time the majority of on-road cars had a solid axle, while off-road cars generally had a gear-type differential.