Radio-controlled model
From Wikipedia, the free encyclopedia
A radio-controlled model (or RC model) is a model that is steerable with the use of radio control. All types of vehicles imaginable have had RC systems installed in them, including cars, boats, planes, and even helicopters and scale railway locomotives.
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[edit] History
Radio control has been around since WWII. The Luftwaffe used controllable winged bombs for targeting Allied ships. During the 1950s pioneering work was done by enthusiastic amateurs to create valve based control units. Originally simple 'on-off' systems these evolved to use complex systems of relays to control speed and direction. The information was encoded by varying the signals mark/space ratio (pulse proportional). Rapidly commercial versions of these systems became available. The tuned reed system brought new sophistication, using metal reed switches to resonate with the transmitted signal and operate one of a number of different different relays. In the 1960s the availability of transistor based equipment led to the rapid development of fully proportional servo-based systems, again driven largely by amateurs but resulting in commercial products. In the 1980s, integrated circuits made the electronics cheap, small and light enough for multi-channel fully proportional control to become widely available.
In the 1990s miniaturised equipment became widely available, allowing radio control of the smallest models, and by the 2000s radio control was commonplace even for the control of inexpensive toys. At the same time the ingenuity of modellers has been sustained and the achievements of amateur modelers using the latest technology has extended to such subjects as gas-turbine powered aircraft, aerobatic helicopters and submarines, to name but a few examples.
Before the days of radio control many models would use simple burning fuses or clockwork mechanisms to control flight or sailing times. Sometimes clockwork controllers would also control and vary direction or behaviour. Other methods included tethering to a central point (popular for cars and hydroplanes), round the pole control for electric model aircraft and control line (USA: u-control for internal combustion powered aircraft.
[edit] Design
RC electronics have three essential elements. The transmitter is the controller. Transmitters have control sticks, triggers, switches, and dials at the user's finger tips. The receiver is mounted in the model. It receives and processes the signal from the transmitter, translating it into signals that are sent to the servos. The number of servos in a model determines the number of channels the radio must provide.
In recent years, electronic speed controllers (ESCs) have been developed to replace the old variable resistors, which were extremely inefficient. They are entirely electronic, so they do not require any moving parts or servos.
In the 1980s, a Japanese electronics company, Futaba, introduced wheeled steering for RC cars. It has been widely accepted along with a trigger control for throttle. It's often configured for right hand users, so the transmitter looks like a gun with a wheel attached on its right side. Pulling the trigger would accelerate the car forward, while pushing it would either stop the car or cause it to go into reverse.
[edit] Mass production
There are thousands of RC vehicles available. Most are toys suitable for children. What separates toy grade RC from hobby grade RC is the modular characteristic of the standard RC equipment. RC toys generally have simplified circuits, often with the receiver and servos incorporated into one circuit. It's almost impossible to take that particular toy circuit and transplant it into other RCs.
[edit] Hobby grade RC
Hobby grade RC systems have modular designs. Many cars, boats, and aircraft can accept equipment from different manufacturers, so it is possible to take RC equipment from a car and install it into a boat, for example. However, moving the receiver component between aircraft and surface vehicles is illegal in most countries as radio frequency laws allocate separate bands for air and surface models. This is done for safety reasons. Most manufacturers now offer "frequency modules" that simply plug into the back of their transmitters, allowing one to change frequencies, and even bands, at will. Some of these modules are capable of "synthesizing" many different channels within their assigned band.
Hobby grade models can be fine tuned, unlike most toy grade models. For example, cars often allow toe-in, camber and caster angle adjustments, just like their real-life counterparts. All modern "computer" radios allow each function to be adjusted over several parameters for ease in setup and adjustment of the model. Many of these transmitters are capable of "mixing" several functions at once, which is required for some models.
[edit] Types
[edit] Aircraft
Radio-controlled aircraft (also called RC aircraft) are small aircraft that can be controlled remotely. There are many different types, ranging from small park flyers to large jets and mid-sized aerobatic models. The aircraft use many different methods of propulsion, ranging from brushed or brushless electric motors, to internal combustion engines, to the most expensive gas turbines. The fastest aircraft, with gas turbines, can reach speeds of up to 250mph.
[edit] Cars
A radio-controlled car is a powered model car driven from a distance. Both gas and electric cars exist, designed to be run both on and off-road. The "gas" cars, unlike their name, don't use gasoline to run. Instead, they rely on nitromethane to get their power. Building, driving, and modifying radio-controlled car kits is a hobby enjoyed by enthusiasts of all ages.
[edit] Helicopters
Radio-controlled helicopters, although often grouped with RC aircraft, are unique because of the differences in construction, aerodynamics and flight training. Several designs of RC helicopters exist, some with limited maneuverability (and thus easier to learn to fly), and those with more maneuverability (and thus harder to learn to fly).
[edit] Boats
Radio-controlled boats are small boats controlled remotely with radio control equipment. There are two main types of RC boat: the sailing boat and the power boat. The latter is the more popular amongst toy grade models. Radio controlled models were used for the children's television program Theodore Tugboat.
[edit] Robotics
The majority of robots used in shows such as battlebots and Robot Wars are remotely controlled, relying on most of the same electronics as other radio-controlled vehicles.
[edit] Power
[edit] Internal combustion
Internal combustion engines for remote control models have typically been two stroke engines that run on specially blended fuel. Engine sizes are typically given in cm³ or cubic inches, ranging from tiny engines like these .02's to huge 1.60's or larger like this. For even larger sizes, many modelers turn to four stroke or gasoline engines (see below.) Glow plug engines have an ignition device that possesses a platinum wire coil in the glow plug, that catalytically glows in the presence of the methanol in glow engine fuel, providing the combustion source.
Since 1976, practical "glow" ignition four stroke model engines have been available on the market, ranging in size from 3.5 cm³ upwards to 35 cm³ in single cylinder designs. Various twin and multi-cylinder glow ignition four stroke model engines are also available, echoing the appearance of full sized radial, inline and opposed cylinder aircraft powerplants. The multi-cylinder models can become enormous, such as this Saito five cylinder radial. They tend to be quieter in operation than two stroke engines, using smaller mufflers, and also use less fuel.
Glow engines tend to produce large amounts of oily mess due to the oil in the fuel. They are also much louder than electric engines.
Another alternative is the gasoline engine. While glow engines run on special and expensive hobby fuel, gasoline runs on the same fuel that powers cars, lawnmowers, etc. These typically run on a two-stroke cycle, but are radically different from glow two-stroke engines. They are typically much, much larger, like this 80 cm³ Zenoah. These engines can develop several horsepower, incredible for something that can be held in the palm of the hand.
[edit] Electrical
Electric power is often the chosen form of power for aircraft, cars and boats. Electric power in aircraft in particular has become incredibly popular recently, mainly due to the popularity of park flyers, and the development of technologies like brushless motors and lithium polymer batteries. These allow electric motors to produce much more energy, rivalling that of fuel powered engines. It is also relatively simple to increase the torque of an electric motor at the expense of speed, while it is much less common to do so with a fuel engine.
In cars and boats, electric power has been the most common form of power for a while. However glow and gas engines are still commonly used as well.
