Mini-Project 1: A Layout-Sketch-Driven Swerve Drivebase

Swerve is the dominant FRC drivetrain, so it is the perfect first mini-project. We will build a square drivebase whose entire footprint is driven by a single variable, then drop in real COTS modules.

Step 1 — Start the layout sketch. Create a Part Studio named Drivebase Layout. Insert the Origin Cube FeatureScript (from FRCDesign.org's curated list) as the very first feature so every downstream Part Studio and Assembly shares a consistent origin. Add a variable feature: #track = 24 in (center-to-center distance between modules). Robot-perimeter rules limit your frame, and a common competitive footprint lands near a 28-30 in square once tube and bumpers are added; a 24 in track keeps you in that neighborhood. Always confirm the limit in the current FRC Game Manual (in the 2026 REBUILT manual the old term 'FRAME PERIMETER' was renamed 'ROBOT PERIMETER').

Step 2 — Sketch the module centers. On the Top plane, draw a center rectangle dimensioned #track x #track. The four corners are your swerve module pivot axes. This single sketch is your master: change #track and the whole robot rescales.

Step 3 — Build the belly-pan and tubes. Sketch the outer frame as 2x1 tube (the FRC standard structural extrusion). REV's MAXTube 2x1 (e.g. SKU REV-21-2162 standard, REV-21-2161 light) has #10 clearance holes spaced 0.5 in apart on the 1 in faces; AndyMark's pre-drilled box tube uses the same #10-on-0.5-in pitch, so models stay cross-compatible. Extrude the four tubes between the corners, then use Tube Converter (Julia's FeatureScripts) to punch the lightening/hole pattern instead of sketching every hole by hand.

Step 4 — Import the modules. Open the Assembly, insert your Drivebase Layout, then use the FRCDesignLib library (inserted via the free FRCDesignApp Onshape plugin) to insert four SDS MK4i swerve modules. The MK4i ships in L1 (8.14:1), L2 (6.75:1), and L3 (6.12:1) drive ratios with a 150/7:1 (~21.43:1) steering ratio and weighs ~6.0 lb with a NEO or ~6.3 lb with a Falcon 500. Pick L1 or L2 for a standard full-weight robot.

Step 5 — Mate with connectors, not faces. This is the load-bearing step. On each tube corner, add an explicit mate connector at the module pivot hole. Use a Fastened mate between each module's mate connector and the corner connector. Because you mated to named connectors (not raw faces), swapping module versions or resizing #track will not orphan the mates.

Verify: open Assembly mass properties to read the bare base weight, leaving plenty of the robot's weight budget for mechanisms.