R/C Glossary

From Rebeldroids Wiki

Several of the droid building techniques depend heavily on R/C tech, which, like most hobbies, has their own vocabulary. Here's the start of a simple glossary. We'll focus on electric vehicles as droids rarely use internal (or external for that matter!) combustion engines.

Also check out the Electrical Glossary, R/C Cars, R/C Transmitters and other pages.

This is a work-in-progress, feel free to add to this info!

Terms

  • 2WD
A two wheel drive vehicle. For an R/C car this is simplest as it requires only one differential.
  • 4WD
A four wheel drive vehicle (you can see where we're going with this). Often considered overkill for most droids, but may be necessary for some designs. Required 2 differentials for a normal car-type R/C vehicle.
  • 8WD
Serious overkill, but some Lego droid builders seriously don't know when to stop!
  • Ah (Amp Hour)
(see Electrical Glossary)
  • Battery
Common R/C batteries are 7.2V or 9.6V, though other voltages exist.
  • Brushed Motor
A very simple electric motor. Generally the more volts you give it, the faster it spins, though often the power is controlled through a PWM signal instead of a pure voltage. The electrical signal to the motor is changed by the use of brushes that change which magnet is energized as the motor spins. One problem is that they aren't efficient in all cases, and the brushes eventually wear out.
  • Brushless Motor
These are more complicated than brushed motors. The magnets in a brushless motor are energized in a particular sequence to make the motor move and provide the desired output. Brushed motors are more efficient and can be more reliable, however they require a more complicated controller to generate the correct signals.
  • Differential
A differential takes input from a driveshaft and sends it to the wheels of the car. A 2WD R/C car would have one differential (typically rear so we don't have to worry about the turning wheels), a 4WD car has two. The key idea of a differential is that it allows the wheels to rotate independently, so that when you turn a tight circle, the outer wheel, which has further to go, can rotate more quickly than the inner wheel. This is also why one of your real car's wheels spins when it's on ice and the other wheel doesn't do anything.
  • Driveshaft
This is a spinning shaft that transmits rotational power from one part of a vehicle to another. Typically this is the output from a transmission to the differential(s) of an R/C car.
  • Drivetrain
The spinny parts of a vehicle. Pretty much the rotating parts of the car between the motor and the wheels.
  • ESC (Electronic Speed Controller)
This is the throttle for an R/C car. It hooks up to the drive battery and regulates the power for the motor. Different types are required for brushed or brushless motors. They typically are rated for specific voltages and amperages (amps).
  • Frame
This is what the rest of the parts of an R/C car are mounted to. At a minimum, you'd need a place to attach the motor and drivetrain and wheels.
  • Gearbox
See Transmission
  • LiFePO4 (Lithium Iron Phosphate)
A battery chemistry. Good energy density can be sensitive to charging/discharging, but considered safer that LIPO batteries. Caution should still be used though.
  • LiPo (Lithium Polymer)
LIPO is a battery chemistry. Known for being able to store a lot of energy, but also very sensitive when charging/discharging and can burn up violently. Special care is needed when using LIPO batteries.
  • Locked Differential
This locks the right and left wheels so that they both spin at the same rate. That means that when cornering, one of the wheels has to slip (because the inside and outside circles traveled by the wheels are different). For a real car that's terrible because it destroys your mileage and tears up your tires, but sometimes it's good for droids. 4WD R/C drivers sometimes like locked differentials so that they don't have to have all wheels on the ground at the same time. It's bad for tracked vehicles because then they're impossible to steer.
  • Mode I
An aircraft transmitter with the throttle on the right stick, used most often outside of the US. This means the right stick won't return itself to center in the forward/backward direction.
  • Mode II
An aircraft transmitter with the throttle on the left stick, used by most R/C pilots in the US. This means the left stick won't return itself to center in the forward/backward direction.
  • Motor
What powers the vehicle! See Brushed and Brushless motors.
  • NiCd (Nickel-Cadmium, aka Nicad)
Older battery chemistry. Cheaper than newer types of batteries they tend to be safer but don't store as much energy. These are usually what you'd see in a basic R/C car set or kid's R/C car. They are often still a good choice.
  • PWM (Pulse Width Modulation)
Pulse Width Modulation is the idea of only sending an electrical signal part of the time. Like a fast square wave. PWM is used in R/C cars in a couple of ways:
1) To control the power to a brushed motor or other circuit. It's easier for modern electronics to send the full voltage part of the time than to send part of the voltage all of the time. So if you want to run at half-power, instead of sending 1/2 the voltage, a PWM controller might send all of the voltage for 1/1000th of a second, then nothing for 1/1000th of a second, then back to full power, etc.
2) It can be used to signal a desired position, like having a servo be all the way left, or all the way right. One direction might be a short "on" pulse and a long "off" pulse. The opposite direction might have a long "on" pulse.
  • Receiver
See Rx
  • Rx (Receiver)
No, not your pain prescription, this is shorthand for "receiver". The Rx is that bit that goes in the car (droid) and passes the signals along to the servos, motors, and whatever else you're trying to radio control in your droid! See R/C Transmitters for more info.
  • Servo
A part that converts an electrical signal into a mechanical movement. R/C cars use servos to steer with. R/C airplanes use servos to control the ailerons and other control surfaces. Droids can use servos to raise and lower arms or open doors. There are many different types of servos for different activities.
  • Shocks
Shocks are used to keep the springs in the suspension from compressing or extending too rapidly.
  • Springs
The part of the suspension that pushes down on the wheels (up on the frame?) When you hit a bump, the spring compresses for a bit, helping smooth the ride and allowing the wheels to stay on the ground.
  • Steering Servo
A servo used to steer the wheels (typically front wheels) of a vehicle.
  • Suspension
The bits of an R/C car that let the wheels move up and down.
  • Transmission
An R/C car typically requires a transmission to reduce the high speed output of the motor to something suitable for the wheels.
  • Transmitter
See Tx
  • Tx
Abbreviation for Transmitter - This is the thing the human holds in their hand and wiggles the controls or presses the buttons on to make the R/C vehicle (droid) do what they want it to. It sends a radio signal to the droid's receiver with the information encoded in that radio signal. See R/C Transmitters for more info.
  • V (Volts)
(see Electrical Glossary)
  • W (Watts)
(see Electrical Glossary)
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