Esk8 Glossary of Terms and Definitions
The below list cannot replace hours of engaged learning but rather is meant as a quick reference to the uninitiated in the world of DIY electric skateboard. Definitions are grouped by topic with a list of posts detailed at the subheading. Each term is linked to a relevant image, diagram or discussion where possible.
Please edit as appropriate
Griptape: Sand paper like adhesive strip attaches to help rider connect to deck.
Deck: This is what you stand on. Commonly made from layered sheets maple or other composite materials. Length and flexibility are a consideration when selecting a deck.
Risers and Shockpads: Plastic or rubber pieces that sit between the Base Plate and Deck to raise or dampen skateboard.
Trucks: Connects the wheels and Bearings to the Deck. Made up of Baseplate, Hanger, and Bushings.
Top Mount: Top of the Baseplate mounts to the bottom of the Deck
Drop Through: Bottom of the Baseplate mounts to the top of the Deck and the Hanger goes through the deck.
Baseplate: Part of truck. Connects Hanger to Deck. Available in various angles, typically 50 or 44 degrees.
Kingpin: Bolt connecting Baseplate and Hanger through Bushings.
Truck geometry defines the carve and the turn, which are different values.
TKPs carve better than RKPs assuming the same setup otherwise. RKPs turn more stable, not as deep, it’s more predictable. Which is why they are better for speed.
Traditional Kingpin (TKP) truck: Pivot axis and king pin axis are not perpendicular to each other
Reverse kingpin (RKP) truck: Pivot axis and king pin axis are perpendicular to each other
Double/dual kingpin (DKP) truck: Two kingpins connecting the hanger to the baseplate through bushings. high turning flexibility may not be suited for fast moving skateboards.
Bushings: Flexible grommet/ring between the kingpin hanger and Baseplate. Effects pivoting and turning stiffness.
[Split Truck Angles]>(Split truck angles, wtf are they? and why should I care? and other stuff about trucks): another name for having two different truck angles, in any configuration
Split Truck Angle Diagram
Pivot Cup: A urethane or plastic cup that fits into the baseplate and allows for the Hanger to pivot against the Baseplate.
Cup Washer: A component of the Truck that goes between the Bushing and the nut and the Bushing and the Baseplate and allows for the Bushings to be compressed or decompressed for the desired performance characteristics.
Hanger: Part of truck connects Axle to Baseplate.
Axle: Runs through the Hanger connecting the wheels/bearings, typically 8mm or 10mm.
Wheels Urethane: Connect to truck hanger with the help of bearings. Typically used for riding on smooth hard surfaces such as streets and hard pathways. Commonly made from Urethane (polyurethane or “thane”) for skate wheels. Urethane wheels have a hardness rating measured in durometer scale. Urethane surrounds the wheel core which connects to the bearings and sometimes pulley. The Urethane and wheel core are part of a single wheel and not designed to be separated.
Wheels Pneumatic: Connect to truck hanger with the help of bearings. Made of individual components, Wheel, Tube, Tire, designed to be separated as needed for maintenance. typically used for riding on varied surfaces not limited to streets or paved pathways. e.g. “Psychotiller SixShooter”
Pneumatic Wheel Thread
Ghost: the action of a urethane sleeve as it delaminates and removes itself from view on a hub driven skateboard at a high rate of speed
Wheel Core: Encircled by material such as urethane. Common Core types are Kegel - circular holes e.g “Torqueboards 110” and Abec - slotted holes e.g “Abec11 Superfly”. Pulley systems will connect to the wheel core.
Bearings: Sit between the wheel or wheel core and the hanger axle. These are what enable the wheel to rotate. Typically made from steel or ceramic balls packed in grease. Common bearing size is “608” and will have either an 8mm or 10mm hole for the axle.
Enclosure: Container designed to protect your electronics attached the board, often to the bottom of the deck.
Direct Drive: Motor sits on hanger and connects to wheel. wheel to motor combination with a 1:1 ratio
Hub Drive: Motor inside wheel. wheel to motor combination with a 1:1 ratio
Belt Drive: Motor mounted off hanger connects to wheel through pulleys and belt.
Gear Drive: Connects motor and wheel through use of meshed gears.
Motor Pulley: Connects to motor shaft and belt/chain, typically smaller toothed gears e.g. 15T
Keyway and Key: The keyway is a slotted section found on a shaft & in the bore of a pulley that houses a key, normally a small rectangular metal block, of the same dimension as the slot. They are used to lock the pulley & shaft together in a fixed position. This is a very reliable method for securing a pulley onto a shaft and can handle high speed & torque output without the pulley slipping.
Wheel Pulley: Connects to wheel and belt/chain, typically higher toothed gear e.g. 36T
Belt: Connects wheel and motor pulley. typically neoprene rubber reinforced with cord. belt thickness and tooth pitch matter.
Motor Mounts: Holds motor away from truck.
ESC: Electric Speed Controller - Circuit board which regulates the speed and braking of motor through the use of field effect transistors (FETs). May or may not contain a switch to power the skateboard.
Motors: connected to ESC and pulley. usually identified by a KV rating and number scheme see Esk8 IQ Math for more detail. e.g. 190kv 6355 motor
Motor Description: Motors are typically described as “6355” or “6374”. these numbers refer to the diameter and length of the motor. e.g. 6355 = 63mm x 55mm without motor shaft.
Stator: Stationary electromagnet in motor which generates rotating magnetic field through the application of electric current.
Inrunner motor: “conventional” configuration where permanent magnets are part of the rotor
Outrunner Motor: In the outrunner (or external-rotor) configuration, the radial-relationship between the coils and magnets is reversed from Inrunner; the stator coils form the center (core) of the motor, while the permanent magnets spin within an overhanging rotor which surrounds the core. esk8 motors like the 6355 are outunner.
Windings: Copper wire wrapped into coils and make up the stator which are energized to generate magnetic fields
Can/Bell Housing: Case surrounding the motor. This can be part of the rotor in outrunner motors.
Poles: number of magnets, connected to the motor rotor some times listed in pairs.
Grub Screws: Also called set screw used to connect two objects without the aid of a nut. In esk8 typically used to attach pulleys to motor shaft. more about fasteners 🔩 Fasteners - What they are, what's in your kit
Battery: Group of cells combined to create dense energy pack. commonly constructed from lithium ion (li-ion) or lithium polymer (lipo) cells connected in series and parallel. connects to BMS and ESC to power devices. See Sk8 IQ3 for more
BMS: Battery Management System - used to control battery charge and discharge.
Charger: Adds power to your battery.
Math and Science of Electric Skateboarding
Pack Definitions: Number of cells in series and parallel. e.g. 12s4p = (12) cells in Series, (4) in Parallel. 10s2p = (10) cells in Series, (2) in Parallel
Series: Cells connected (+) to (-), increasing voltage
Parallel: Cells connected (+) to (+) and (-) to (-), increasing capacity. e.g “P-group” is a number of cells connected in parallel.
C rating: Describes how quickly a battery can be discharged
Voltage: Measure of energy potential or electric pressure. e.g 3.6v
Nominal Voltage: Average voltage output of a cell when charged.
Amp: Short for Ampere. Base unit for electrical current
Current: Electric flow in amps or amp hours e.g. 12amps
Amp hours: Number of amps that can be continuously discharged for (1) hour
Milliamps mA: 1,000 of an Amp. e.g (12)Amps = (12,000)mA/(1,000)
Watts: Volts * Amps e.g. (12)a * (36)v = (432) Watts
ERPM Electrical Revolutions Per Minute - speed motor rotates multiplied by magnet poles. e.g. (60,000)ERPM.
Kv Rating: unloaded revolutions per minute when (1) volt is applied. e.g. 190Kv motor will rotate (6,840) times in a minute when (36) volts are applied without any additional weight on the motor. NOT kilovolts (kV) - little “k” big “V” - which is (1,000) Volts.
Electromotive Force (emf): Electrical action produced by an energy source, such as a generator or battery measured in Volts. Technically this is the potential difference and can suppy current if connected to a resistance. On the small scale, the potential difference creates an electric field that exerts force on charges, causing current. We thus use the name electromotive force, abbreviated emf.
video description of back emf
Back emf: Electromotive Force (emf) generated by a spinning motor. Also called Counter-electromotive force (CEMF).
When something like a refrigerator or an air conditioner (anything with a motor) first turns on in your house, the lights often dim momentarily. To understand this, realize that a spinning motor also acts like a generator. A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.
At the motor’s operating speed, enough current flows to overcome any losses due to friction and other sources and to provide the necessary energy required for the motor to do work. This is generally much less current than is required to get the motor spinning in the first place.
Firmware: Program embedded directly on hardware, like an ESC, for low level functionality which does not typically require regular user interaction e.g vesc V3.103
Motor Current Max: Amp draw from the motor - limited by the ESC maximum current draw.
Motor Current Max Brake: Amps fed back through the ESC to the Battery when braking with Motor.
Battery Current Max: Maximum amps taken from the battery - this is limited by the battery, BMS, or ESC.
Battery Current Regen: Max amps fed back through the ESC to the Battery. always lower or equal to motor current. DC current you are allowing your battery to charge at while braking
Low Speed Brakes: how quickly device will slow at slower speeds. Regulated by Battery Current Regen value in ESC
Duty Cycle: In brushless direct current motors the duty cycle is the percentage of time that current is taken from the battery.
Cogging: the motors will stutter until they start to revolve in the direction you want
FOC: Field Oriented Control or Vector Drive - Brushless Motor uses magnetic field to identify motor position.
BLDC: Brushless Direct Current motor- electric motor that use magnet pairs and stator to rotate.
UART: Universal Asynchronous Receiver Transmitter - as the name suggests it is a standard to send and receive serial data. Instead of a clock signal, the transmitting UART adds start and stop bits to the data packet being transferred.
When the receiving UART detects a start bit, it starts to read the incoming bits at a specific frequency known as the baud rate. Both UARTs must operate at about the same baud rate and can only differ by about 10% before the timing of bits gets too far off. If there are communication problems between to UART such as ESC and Bluetooth dongle, it is good to validate both devices are operating on same bps such as 9600.
bps: Bits Per Second - measure of data transfer speed
CAN BUS: Controller Area Network - Typically a wire used for individual components to communicate synchronously. e.g. CAN BUS cable may be used to connect (2) ESC so they may utilize a single communication module such as a remote to control both devices.
Loop Key: Key made from XT90s connector placed inline between the battery and ESC to complete the electrical circuit used to turn on/off the electric skateboard and reducing chance of spark
Redundancy: [pending esk8 application definition consensus]
Surface-Mount Technology (SMT): is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). In industry, it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board.
Metal-oxide-semiconducter field-effect transistor (MOSFET) “Fet(s)” : Are the basic building block of modern electronics and most common power device. They require almost no input current to control the load current. FETs also have faster switching speed, much smaller size, consume significantly less power, allow much higher density, and are cheaper than bipolar transistors. In context of an ESC, the job of the MOSFET is to switch the three phases of the brushless motor to make it spin