Wednesday, 30 January 2013

Electric models
Electrically powered models utilise 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 by the transmitter - the more you pull the trigger, the faster it goes. The voltage is "pulsed" using transistors to produce varying output with smooth transitions and greater efficiency. Electronic speed controllers use solid state components to regulate duty cycle, adjusting the power delivered to the electrical motor. In addition, most 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. Mechanical speed controllers use a network of resistors 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 because they are actuated by servos, waste energy in the form of heat from the resistors, commonly become dirty and perform intermittently, and lack a dedicated braking ability. They appear only in vintage RC models, and are now essentially obsolete. Most electric cars up to recently used brushed motors but now many people are turning to brushless motors for their higher power output and because they require much less maintenance. They are rated either in relative turns or Kv. The Kv number tells how many RPM the motor will turn per volt, assuming no load and maximum efficiency. However, the ability of the system to put out power is dependent on the quality of the batteries used, wires and connectors supplying power. Due to their power, brushless motors are also used in bigger monster trucks and 1/8 nitro-powered buggies that have been converted to electric. High quality brushless systems can be much more powerful than nitro and can accomplish feats such as standing backflips when installed in a monster truck, most notably the HPI Savage Flux. Some 1/5 scale gas to electric conversions are in production but are uncommon due to high price.

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