Reference
Every word on this site that is reasonable to stop at, in one plain sentence each. Terms on the calculators link here, and hovering one shows the definition without leaving the page.
Turning force: how hard something twists, rather than how hard it pushes.
A long spanner undoes a tight bolt more easily than a short one, with the same hand force, because torque is force multiplied by the distance from the pivot.
See also: Pound-inch (lb·in), Newton-metre (N·m), Stall torque
A unit of torque: one pound of force pushing one inch from the pivot.
Two pounds at one inch, or one pound at two inches, both give two pound-inches. This site uses it because VEX parts are measured in inches.
See also: Torque, Newton-metre (N·m)
The metric unit of torque. One newton-metre is about 8.85 pound-inches.
VEX publishes motor torque in newton-metres, so the conversion shows up constantly. A 100 RPM cartridge stalls at 2.1 N·m, which is 18.6 lb·in.
See also: Torque, Pound-inch (lb·in)
How fast energy is used. A V5 motor is either 11 watts or 5.5 watts.
The competition rules cap total motor watts on the robot, which is why motor count alone is not the limit any more.
See also: Joule (J), Motor power cap
An amount of energy. A watt is one joule every second.
Useful for launchers: work out the energy a game object needs, divide by the watts you have, and you get the fastest possible cycle.
See also: Watt (W)
Revolutions per minute: how many full turns something makes in a minute.
A V5 cartridge is named by its RPM. Higher RPM means faster and weaker, because the same motor is geared differently inside.
See also: Cartridge
A speed. The VEX field is 12 feet across, so a robot at 4 ft/s crosses it in about three seconds.
The turning force a motor makes when it is pushing so hard it has stopped turning.
It is the most torque a motor can ever make, and it makes it while going nowhere and getting hot. Sizing a mechanism at anything near stall means it holds the load but barely moves it.
See also: Torque, Free speed
How fast a motor spins with nothing attached to slow it down.
The real speed is always lower, because any real load costs speed. Between free speed and stall the trade is roughly a straight line.
See also: Stall torque
The coloured plastic gear insert in a V5 motor that sets its speed.
Red is 100 RPM and strongest, green 200, blue 600 and fastest. Same motor, different gearing inside, so torque and speed trade exactly.
See also: RPM, Stall torque
The rule limiting total motor watts on the robot, and on the drivetrain by itself.
There are two separate caps. Passing one and failing the other still fails inspection.
See also: Watt (W)
How much of the motor power survives the gears and bearings on the way out.
Roughly 95% per clean gear mesh, so a two stage reduction lands near 90%. Anything that binds or rubs takes more.
How many turns of the input make one turn of the output.
A 7:1 reduction means seven motor turns per output turn: seven times slower and about seven times stronger. You never get both.
Gearing that trades speed for strength: slower output, more torque.
The opposite is an overdrive, which is faster and weaker. Lifts almost always want a reduction.
See also: Gear ratio
The size a gear behaves as, measured where its teeth actually mesh.
Not the same as the outside diameter, which includes the tips of the teeth. Centre distance between two gears uses pitch diameters, so using the outside one puts the gears too far apart.
See also: Centre distance
How far apart two gear or sprocket shafts sit.
For VEX gears it is (teeth + teeth) divided by 48 inches, and it has to land on the half inch hole grid or you cannot build it.
See also: Pitch diameter
Two or more gear pairs in a row, so their ratios multiply.
A 3:1 followed by another 3:1 gives 9:1. It is how big reductions are built without a single enormous gear.
See also: Gear ratio
The small amount of free play before gears or chain actually start pushing.
It shows up as a mechanism that wobbles slightly before it moves, and it is why an arm can sag a little even when the motor is holding.
The main VEX structural bar, shaped like a C so it resists bending.
Named by hole count: a 1x2x1 has a two-hole web with one-hole sides.
See also: Hole spacing
VEX holes sit half an inch apart, in a square grid.
Almost every awkward measurement on a VEX robot comes back to this. If a distance is not a multiple of 0.5 inches, it will not mount on standard holes.
See also: Centre distance, C-channel
A threaded post that holds two pieces of structure a fixed distance apart.
A ring that clamps to a shaft to stop it sliding through its bearing.
The point where metal bends and stays bent instead of springing back.
Well below where it snaps. A shaft that has yielded is permanently twisted and will never run true again.
The single point the whole robot balances around.
Low and central is stable. Every heavy thing you lift drags it upward, which is why a robot is easiest to tip with its lift raised.
How spread out a set of measurements is around their average.
Small means repeatable. About two thirds of attempts land within one standard deviation of the average, and about 95% within two.
See also: Confidence interval
The range the true answer probably sits in, given how little data you have.
Seven successes out of nine is 78%, but with only nine tries the honest range is about 45% to 94%. The interval is what stops a lucky run looking like a fact.
See also: Standard deviation
What something is worth on average across many tries, not what it is worth when it works.
A routine scoring 20 points that works half the time is worth 10 a match. That is the number to compare against a boring routine that always works.
A number for how much grip there is between two surfaces.
Higher means more grip. It decides how hard a robot can push before the wheels simply spin, and no amount of extra motor power changes it.