A radio-controlled car (R/C car) is a powered model car driven from a distance via a radio control system. Inputs from joysticks (or a wheel and a trigger) on a transmitter are sent to the car's onboard receiver. The receiver interprets the radio signals and sends electrical pulses to the servo and electronic speed controller, making the model turn its wheels and the run the motor. Radio-controlled cars can range from simple "stop and go" toys to competitive racing models, which feature all the complexity and adjustability of their full-size counterparts. Building, driving, and modifying radio-controlled car kits is a popular hobby.
Radio-controlled (or R/C) cars are usually categorized as either "toy" or "hobby" grade. Remote control vehicles are usually of one of two types: control of a vehicle by radio transmission or by a wire connecting between the transmitter and car. This article focuses on the radio-controlled vehicle category, both toy and hobby grades.
Cars are powered by various sources. Electric cars are powered by small but powerful electric motors and rechargeable nickel-cadmium, nickel metal hydride, or lithium polymer cells. There are also brushed or brushless electric motors. Most fuel-powered models use glow plug engines, small internal combustion engines fueled by a special mixture of nitromethane, methanol, and oil (in most cases a blend of castor oil and synthetic oil). These are referred to as "nitro" cars. Recently, exceptionally large models have been introduced that are powered by small gasoline engines, similar to weedwhacker motors, which use a mix of oil and gasoline. Electric cars are generally considered easier for the novice to work with compared to fuel-driven models, but can be equally as complex at the higher budget and skill levels.
In both of these categories, both on-road and off-road vehicles are available. Off-road models, which are built with fully-functional off-road suspensions, can be used on various types of terrain. In comparison, on-road cars, which generally have a limited or non-existent suspension, are strictly limited to smooth, paved surfaces.
The term "toy" or "toy-grade" in regards to radio control cars is used to describe vehicles of the pre-assembled type generally found in discount stores and consumer electronics stores. They are often colloquially referred to as "Radio Shack cars". Some toy-grade R/C models may also be found in hobby shops in an attempt to appeal to young users. Generally speaking, a toy R/C is meant as a child's plaything.
In recent years, hobby-grade "ready-to-run" (or "RTR") models have become available from every major manufacturer of radio-controlled cars, attracting many hobbyists who would otherwise have purchased a pre-assembled car. Vehicles of this type need little or no final assembly and in many cases, the bodies are shipped painted and trimmed, requiring little work from the owner before they can be used (other than purchasing and installing batteries). A number of cars and trucks are presently available only in ready-to-run form, such as the Traxxas Revo, a nitro-powered model truck, or the Redcat Racing Volcano, also a nitro-powered model truck. The growing popularity of the RTR vehicle has prompted manufacturers to introduce kit versions of their RTR cars that include factory upgrades but have no radio gear installed and often no motor or speed controller.
Electric-powered models use high capacity compact batteries to drive brushed or brushless motors via an electronic speed control(ESC). Electric models tend to be lighter than nitro models, due to having fewer components in the drive system. Electric cars are more consistent, and have more torque than nitro models. Also, they also have faster throttle response. Electric batteries, however, take some time to charge; peak chargers can charge cells in about fifteen to forty-five minutes. Stock top speeds for electric models are around 30 mph, but depend greatly on the model and motor. Faster speeds are available through upgraded components such as brushless motors or lower-turn brushed motors and LiPo Batteries. A few highly modified electric cars are capable of speeds over 100mph, where aerodynamics come into play and care must be taken to ensure that the car will not lose control or literally lift off the ground.
Routine maintenance usually consists of cleaning, inspecting the model car for damages, and replacing any parts that have been damaged or worn during use. High-performance electric motors must be allowed to cool down after use to avoid demagnetizing the permanent magnets. In terms of long-term maintenance of the motor, the application of motor cleaning solution is needed between runs to avoid wear from dirt and dust. Also, the bearings (or bushings) in the motor must be re-oiled periodically. Replacing the motor brushes and springs and cutting its commutator is also sometimes required using special lathes designed for this purpose.
Fuel-powered engines allow model cars to reach moderate speeds unmodified. Maximum power is generally achieved at medium to high speeds, and a slightly slower throttle response than electrically powered vehicles is to be expected. Electric motors effectively produce instantaneous torque, where nitro engines, like full-sized gasoline engines, take time for the engine to spool up and for the clutch to engage. Nitro- (and fuel) powered cars may be refueled and returned to action in a few seconds, as opposed to electrics needing to remove the body shell and battery fasteners to replace a discharged battery. Nitro cars are completely air cooled, and may be run continuously with no need to take breaks for cooling down. Nitro cars tend to be larger than electric cars on average, because affordable high-performance electronics are only generally available in 1:10 scale and smaller. However, scale equivalents do exist in both nitro and electric forms, such as the RC10T4 and the GT2
Nitro-powered cars operate like full-sized fuel vehicles more than their electric counterparts do. The sound of the engine and design of the drive train are main selling points to nitro enthusiasts. However, their exhaust contains unburned oil, which usually ends up coating the chassis. This, in turn, requires more cleaning than an electric-powered equivalent. Cleaning is usually achieved by the use of compressed air blowers and solvents (such as denatured alcohol). Tuning a fuel-powered vehicle requires learning to maintain optimum performance and fuel economy, and to minimize engine wear and overheating, even in ready-to-run vehicles.
Because of higher stock performance and their ability to be driven for longer periods of time, mechanical wear in nitro vehicles is generally greater than in electric vehicles. In addition, the increased speed and weight of fuel-powered vehicles generally lead to higher speed collisions, causing greater damage to the collided vehicles, and a greater degree of safety concerns needs to be taken into account. However, nitro vehicles are more durable due to stronger components to sustain the greater stresses of more power.
A large industry of aftermarket manufacturers produce upgrade or hop-up parts for hobby-grade cars. Upgrades range from mere improvements to the longevity of R/C car parts, to all-out performance enhancements. A number of hobbyists create their own upgrades for sale via classifieds and online forums.
"Ready-to-run" cars can be purchased, which leave the factory in a pre-tuned condition that affords for good racing performance without prior adjustment. However, those vehicles should still be inspected for loose parts prior to operation as stated in many manuals. Alternatively, vehicles can be purchased that are either in kit form or are partially assembled, which are built and tuned by the owner prior to use, but most of the time, the owner will have to buy radio gear, and sometimes even an engine when they buy a kit.
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 in pistol grip form, a trigger for throttle and a wheel for turning, 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 control positions 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, generally through adjustable turnbuckle linkages. Servo savers are integrated into all steering linkages and some nitro throttle linkages. A servo saver is a flexible link between the servo and its linkage that protects the servo's internal gears from damage during impacts or stress.
Most electric cars up to recently used brushed motors but now many people are turning to brushless motors for their power and because they require much less maintenance. They are rated either in turns or Kv. The Kv number tells how many RPM the motor will turn per volt. However, the ability of the system to put out power is dependent on the quality of the batteries used. Due to their power, brushless motors are also used in bigger monster trucks and 1/8 buggies that have been converted to electric.
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-.28 cubic inch engines.
Several early commercially viable R/C cars were available by mid-1966, produced by the Italian company El-Gi (Elettronica Giocattoli) from Reggio Emilia. Their first model, a 1:12 Ferrari 250LM was available in the UK in December 1966, through importers Motor Books and Accessories, St. Martins, London, and early in 1967 through Atkinson's model shop in Swansea. This model was followed by El-Gi's 1:10 Ferrari P4, first shown at the Milan Toy Fair in early 1968.
In the mid-late 60s a British company, Mardave, based in Leicester, began to produce commercially viable RC Cars. Their first cars were nitro- or gas-powered cars sold in the local area in the early 70s.
In the early 70s several commercial products were created by small firms in the US. Most of these companies began as slot car companies and with the wane in popularity of that genre moved into the R/C field. Among these were Associated Electrics, Thorp, Dynamic, Taurus, Delta, and Scorpion. These early kits were 1/8 scale nitro-powered (then called gas) aluminum flat pan cars powered by a .21 or smaller engine. The bodies for these cars were made of polycarbonate (the most popular made of Lexan). The most popular engine was the K&B Veco McCoy. The primary sanctioning body for races for these cars was Remotely Operated Auto Racers (ROAR). In 1973-74, Jerobee, a company based in Washington State, created their 1/12 nitro car using a Cox .049 engine. Several aftermarket companies created parts for this car including clear Lexan bodies, heat sinks, and larger fuel tanks. This scale evolved into 1/12 scale electric racing when Associated Electrics created the RC12E in 1976-77. Jerobee became Jomac and created their own electric kit.
In 1976, the Japanese firm Tamiya, which was renowned for their intricately detailed plastic model kits, released a series of elegant and highly detailed, but mechanically simple electric on-road car models that were sold as "suitable for radio control". Although rather expensive to purchase, the kits and radio systems sold rapidly. Tamiya soon began to produce more purpose-built remote-controlled model cars, and were the first to release off-road buggies featuring real suspension systems. It was this progression toward the off-road class that brought about much of the hobby's popularity, as it meant radio-controlled cars were no longer restricted to bitumen and smooth surfaces, but could be driven virtually anywhere. The first true Tamiya off road vehicles were the Sand Scorcher and the Rough Rider, both released in 1979, and both based on realistic dune buggy designs. Tamiya continued to produce off road vehicles in increasing numbers, featuring working suspensions, more powerful motors, textured off-road rubber tires and various stylized "dune buggy" bodies. They also produced trucks, such as the Toyota HiLux Pickup, that featured realistic 3 speed gearboxes and leaf-spring suspension systems. All of these models were realistic, durable, easy to assemble, capable of being modified, and simple to repair. They were so popular that they could be credited with launching a boom in radio-controlled model cars in the early to mid 1980s, and provided the basis for today's radio-controlled car market. Popular Tamiya models included the Grasshopper and the Hornet dune buggies as well as the Blackfoot and Clodbuster monster truck models. The earliest Tamiya models, particularly the early off roaders, are now highly sought after by vintage R/C collectors and can fetch prices of up to US$3000 on internet auction sites if still in mint, unbuilt form. Acknowledging their continued popularity, several of the early kits have even been re-released by Tamiya during 2005–2007, with a few alterations.
A British firm, Schumacher Racing, was the first to develop an adjustable 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. Team Associated followed suit with the introduction of the RC10 off-road racing buggy in 1984 (see below).
In 1984, Associated Electrics, Inc. of Costa Mesa, California introduced the RC10 off-road electric racer; this model was a departure from Associated Electrics' regular line of nitromethane-powered on-road race cars. Designed as a high-grade radio controlled car, the chassis of the RC10 buggy was manufactured from anodised, aircraft-grade aluminium alloy. The shock absorbers were machined, oil-filled and completely tuneable; they were also produced from the same aluminium alloy. Suspension control arms were manufactured from high-impact nylon, as were the three-piece wheels.
Optional stainless steel miniature ball bearings were sometimes incorporated in RC10 wheels and transmissions. The RC10 transmission contained an innovative differential featuring hardened steel rings pressed against balls - which made it almost infinitely adjustable for any track condition. The RC10 quickly became the dominant model in electric off-road racing.
In 1986, Schumacher Racing Products released their CAT (Competition All Terrain) vehicle, widely considered the best four wheel drive off-road "buggy" racer of the time. The CAT went on to win the 1987 off-road world championship. This car is credited for sparking an interest in four-wheel-drive electric off-road racing.
Gil Losi Jr., whose family ran the "Ranch Pit Shop R/C" racetrack in Pomona, California, turned his college studies toward engineering, primarily in the field of injection molded plastics, leading to his foundation of Team Losi. When the JRX-2, the first Team Losi buggy, was released, it initiated a rivalry with Team Associated that continues to this day. Team Losi went on to secure a number of achievements, which included the industry's first all-natural rubber tires, the first American-made four-wheel-drive racing buggy, and an entirely new class of cars, the 18 scale Mini-T off-road electrics.
Although Losi and Associated seemed to dominate much of the American market, Traxxas, (another American company, famous for the T-MAXX and the REVO 3.3), and Kyosho (from Japan), were also making competitive two-wheel-drive off-road racing models. Although Losi and Associated were close rivals in the USA, Schumacher off-road models continued to be popular amongst European hobbyists.
Electric and nitro cars have come a long way in terms of power. Electric cars have gone from non-rebuildable brushed motors and ni-cad batteries to brushless motors and LiPo. Nitro cars have gone from small engines to huge .32 engines that are used in big monster trucks.