18" Footprint Checker
Does the robot fit the 18-inch starting cube once the wheels, screw heads and motors are counted rather than just the frame?
Inputs
Outer edge to outer edge. A span of N holes is exactly N × 0.5".
Tallest point, including anything sticking up.
Wheels, motors, screw heads, collars. Per side, so it gets counted twice.
Per end. Also counted twice.
Results
Fits the cube?
—
Overall length
—in
Overall width
—in
Overall height
—in
Tightest dimension
—
Margin there
—in
Overall width in hole spacings
—
Everything has to fit inside this at the start of a match, including anything sticking out past the frame.
When you would use this
We are not sure our robot will pass inspection.
Measure the frame, then add whatever sticks out past it on each side: bolt heads, standoffs, an intake sitting proud. The tightest dimension is the one inspection will find.
Our intake sticks out and we want to know if it still fits.
Put the overhang in the sides or ends box rather than guessing. It counts double, because it sticks out on both sides of the measurement.
We want to know how much room we have left for a bumper or a guard.
The margin figure is exactly that: how many inches you can still add before the tightest dimension reaches the limit.
How this is calculated
The arithmetic is deliberately dull. The value is in what gets counted.
overall length = frame length + (2 × sticking out past each end) overall width = frame width + (2 × sticking out past each side) fits when every dimension ≤ 18"With your numbers
Note the doubling. A team measures a wheel sticking out an inch and a half on one side, subtracts that from eighteen, and concludes there is plenty of room, forgetting the identical wheel on the other side. Three inches of a fifteen-inch frame's allowance disappears that way.
What people forget to measure
- Wheels are wider than the frame. Usually the single biggest contributor, and the easiest to leave out because it feels like part of the drive rather than part of the size.
- Screw heads and nylock nuts. A quarter inch each side, everywhere, and they are on the outside precisely where it costs you.
- Motors and shaft collars. Motors hung outboard, and collars on shaft ends, both stick out past the structure.
- Anything that sags. A mechanism held up by a rubber band at rest may not still be inside the cube once it settles.
The diagonal does not matter
A common worry: "my robot is 17 by 17, but the diagonal is 24 inches. Is that legal?" Yes. The robot has to fit inside a cube in the orientation it starts in, and a 17 × 17 rectangle sits inside an 18 × 18 square comfortably. The sizing tool goes around the robot; it is not rotated about it.
Leave yourself room
Designing to exactly eighteen inches means any build tolerance, any slightly bent piece of structure, and any washer you added later puts you over. The robot that measures a comfortable seventeen and a half passes inspection at every event without a conversation.
Sources & assumptions
The 18" starting envelope is from the Override2026-27 game manual. The 0.5" hole spacing is a verified VEX standard, so a span of N holes is exactly N × 0.5".
C-channel outer dimensions are deliberately not built in. They depend on material and thickness, VEX does not publish them in a form I could verify, and a guessed figure here would hand teams a false pass at inspection. Measure your frame and enter what you measured.
- V5RC Override Game Manual v1.1 (2026-27) — checked 2026-08-17
- VEX Robotics — C-Channels (8 sizes) — checked 2026-08-17
Save this run, and compare
Keeps what is on screen so you can change something and see both sides of the change. Saved in this browser only, never uploaded.
Save this as evidence
Collects what you entered, what came out, how it was worked out, and anything the tool flagged, with a timestamp and a version so someone else can reproduce it.
This is evidence, not a notebook entry. It deliberately does not write your problem statement, your reasoning, or your conclusion, because under RECF rules an Engineering Notebook has to be the students' own work and no tool may generate or organise its content. Take the numbers, decide what matters, and write it yourself.