Before modeling any single mechanism in detail, lay out the whole robot from above. Where does the Brain go? Where are the batteries? Does the arm clear the intake at full extension? Catch these problems in CAD, not after cutting metal.
CAD → Notebook connection: A top-down robot layout with the 18"×18"×18" start constraint overlaid is exactly the screenshot judges want to see in your "Identify the Problem" section. It proves you analyzed physical constraints before designing.
📐 Interactive Robot Layout Planner
Click each zone to see placement guidelines. This is a top-down view of a typical VRC robot footprint.
📐 Top-Down Robot Footprint (18" × 18")Click a zone
Drivetrain
Electronics
Intake
Arm/Lift
18" limit
📦 Packaging Rules for VRC
🚗 Drivetrain
Goes along the sides and back. Keep motors outboard of the wheelbase for access. Leave 0.5–1" clearance between wheel and frame for encoder pods.
⚡ Electronics
V5 Brain and battery as low and centered as possible. Cable runs ≤12" from brain port to motor. Shield from game piece collisions with a polycarbonate panel.
🔄 Intake
Front-mounted. Must fit within 18" horizontally at start position. Model the full swept volume (not just the resting position) to check clearance against other mechanisms.
💪 Arm / Lift
Model the full travel range using Onshape's motion simulation. Check interference at every angle: does the arm hit the intake? The brain? The field wall at max extension?
⚖ Center of Gravity Estimator
A robot with CG near its geometric center is more stable. Onshape calculates actual CG from mass properties, but this tool gives you a quick estimate during layout.
⚖ Quick CG Estimate
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The 18"×18"×18" check: In Onshape, create a cube Part Studio that is exactly 18"×18"×18". Insert it as a reference part in your assembly. Position your robot inside it. Anything that sticks out of the cube at the start of a match is a re-inspection red flag. Do this before you build, not at the inspection table.
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OFFICIAL ONSHAPE — VEX ROBOT DESIGN RESOURCES
VEX V5 Parts Library with correct mass properties, Learning Center robotics curriculum
⚙ STEM HighlightEngineering: Systems Layout & Spatial Constraint Management
Robot layout design is a spatial constraint optimization problem. Available volume is fixed (18″ cube). Components have fixed minimum sizes. The layout must satisfy: center of mass within tipping margin, cable routing without interference, access for maintenance, and weight distribution for traction. Professional mechanical engineers call this packaging — fitting required components into available space while satisfying all constraints. CAD layout catches spatial conflicts before fabrication; physical trial-and-error catches them after.
🎤 Interview line: “We plan robot layout in Onshape before cutting any metal. By importing all component models and applying correct dimensions, we can verify clearances, cable routing paths, and center-of-mass position before building. Our layout review process caught three component conflicts in our V2 design that would have required a full rebuild if discovered during assembly.”
Why is robot layout planning in CAD more effective than planning during physical assembly?
⬛ CAD is faster to modify than physical components when conflicts are found before fabrication
⬛ VRC rules require CAD documentation before building
⬛ Physical assembly always works the first time if you have enough parts
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Notebook entry tip:Build & Program — Orange slide — Include a top-down layout view from Onshape in your Build section, annotated with: component locations, estimated center of mass, cable routing paths, and maintenance access points. Judges want to see evidence that your layout was planned — a labeled CAD top-view takes 10 minutes to create and is one of the most effective notebook entries an engineer can produce.