Frame Construction

The frame is the foundation that everything else bolts to. It carries the drivetrain, supports every mechanism, absorbs hits from other robots, and defines the robot's perimeter. We build our frames from aluminum box tube connected with gussets, which is the standard construction method for competitive FRC robots.

Tube sizes

Tube	Wall thickness	When to use
2x1 (0.0625" wall)	Thin wall	The standard for frame rails, superstructure, and most structural members. Light and strong enough for nearly everything.
2x1 (0.125" wall)	Thick wall	High-load areas like drivetrain rails that take direct impacts, or anywhere you need to tap threads directly into the tube wall. Heavier but significantly stiffer.
1x1 (0.0625" wall)	Thin wall	Lighter mechanisms, superstructure cross-members, intake arms, elevator stages, and anywhere the loads are moderate and you need to save weight.
1x1 (0.125" wall)	Thick wall	Same applications as thin wall 1x1 but where more rigidity is needed.
2x2 and 1.5x1.5 (0.0625" wall)	Thin wall	Telescoping applications (climbers, elevators) where one tube needs to slide inside another. Sized so that 1x1 fits inside 1.5x1.5, and 1.5x1.5 fits inside 2x2.

For the drivetrain frame rails, 2x1 is the default. For superstructure and mechanisms, choose between 2x1 and 1x1 based on the load. If you're not sure, 2x1 is the safer choice and you can lightweight it later by pocketing or switching to 1x1 after you've verified the loads are manageable.

Pre-drilled (punched) tube

Pre-drilled tube comes with a grid of holes already punched on a consistent pitch (typically 0.5" spacing with #10 clearance holes). This eliminates the need to measure and drill holes for every gusset, mount, and bracket on the frame.

Why it matters: On plain tube, every hole has to be individually measured, center-punched, and drilled. Misaligned holes mean gussets don't fit, parts don't line up, and you spend time fixing mistakes. Pre-drilled tube puts every hole exactly where it needs to be, which makes assembly faster and more accurate.

Available from: WCP (0.5" pitch, #10 clearance), VEX (VersaFrame, 1" pitch), AndyMark (0.5" pitch). We use WCP punched tube because the 0.5" pitch gives more mounting flexibility than 1" pitch.

How to use it:

• Cut tube to length with a chop saw (or, if we have a horizontal bandsaw in the future). No other machining needed for basic frame construction.

• Bolt gussets directly to the pre-drilled holes. No match drilling required for standard connections.

• For swerve module mounting, the SDS MK5i bolts directly to 2x1 tube with 10-32 clearance holes on 0.5" pitch, which is exactly what WCP punched tube provides.

Pre-drilled tube is one of the biggest time-savers available to FRC teams. A drivetrain frame that used to take a full day of measuring, drilling, and squaring can be assembled in a few hours with punched tube and COTS gussets. Buy it pre-drilled unless you have a specific reason to use plain tube.

Gussets

Gussets are the plates that connect tubes together at joints. They're what give the frame its rigidity. Without gussets, tubes bolted end-to-end would flex and fold at every joint.

COTS gussets

WCP, VEX, and AndyMark all sell pre-made gussets in standard angles and configurations.

Type	Use
90 degree corner gusset	Connecting two tubes at a right angle. Frame corners, T-joints, cross-members.
Straight / joiner gusset	Splicing two tubes end-to-end to make a longer member.
T gusset	Connecting a tube perpendicular to the middle of another tube.
Angled gussets (45, 60, 120, etc.)	Diagonal bracing, angled superstructure members.
3-4-5 gussets	Creating triangulated bracing with specific right-triangle proportions. WCP and AndyMark sell "steep" and "shallow" versions for the two non-right-angle corners.

COTS gussets are cheap, precise, and fast to install. Use them for standard connections and save custom gusset design for places where no COTS option fits.

Custom gussets

Tube plugs

Tube plugs are solid aluminum blocks that press or bolt into the end of a tube. They serve two purposes: they give you a solid surface to bolt into at the end of a tube (where the thin wall of the tube itself isn't enough), and they close off the end of the tube so debris doesn't get inside.

WCP sells tube plugs for 1x1, 1.5x1.5, 2x1, and 2x2 tubes. The plugs are tapped #10-32 on five faces, which means you can bolt gussets, plates, or other components directly to the end of a tube without drilling through thin wall material.

For thin-wall tube (0.0625"), tube plugs are especially important at high-load connections because the thin wall alone doesn't have enough material to hold a bolt securely.

Frame layout

The drivetrain frame is typically a rectangle of 2x1 tube with the swerve modules at each corner. Beyond that, the frame layout depends on the game and the mechanisms the robot needs.

Drivetrain frame first. The drivetrain perimeter gets designed and built in week 1. The frame size is determined by the game's size constraints and the space needed for mechanisms inside. Swerve modules mount to the corners.

Superstructure second. The superstructure is everything above the drivetrain frame that supports mechanisms (elevator mounts, arm pivots, shooter platforms). It bolts to the drivetrain frame using gussets, tube plugs, or through-bolts.

Design tips:

Tip	Why
Triangulate wherever possible	A rectangle is weak (it can rack into a parallelogram). Adding a diagonal brace or triangulating with gussets makes the structure rigid.
Don't cantilever superstructure	If a tall vertical member only bolts to the frame at the bottom, it will flex when the robot gets hit. Support it with gussets, diagonal braces, or a second attachment point higher up.
Plan for bumper mounting	Bumper mounts need to be part of the frame design, not an afterthought. Leave space and bolt holes for bumper brackets on the frame perimeter.
Leave access for wiring	Route wires through the inside of the frame by drilling holes in the tubes. Plan these holes during CAD, not during assembly.

Squareness

A frame that isn't square will cause problems with everything mounted to it: swerve modules won't align, mechanisms won't fit, and the robot will drive crooked. Verifying squareness during assembly is critical.

How to check: Measure the diagonals of the rectangular frame. If both diagonals are equal (within about 1/16"), the frame is square. If they're different, loosen the gusset bolts, push the frame until the diagonals match, and retighten.

How to maintain squareness: Assemble the frame on a known-flat surface (a welding table, a granite surface plate, or at minimum a flat shop table). Tighten bolts in a pattern that doesn't pull the frame out of square (tighten one bolt per corner in a star pattern, then go back and fully tighten everything).

Check squareness before bolting the bellypan on. The bellypan locks the frame shape. If the frame is out of square when the bellypan goes on, it stays out of square.

Weight management

The frame and superstructure are some of the heaviest components on the robot, so weight savings here have a big impact.

Strategy	How
Use thin-wall tube where thick-wall isn't needed	0.0625" wall 2x1 is roughly half the weight of 0.125" wall. Use thick wall only where loads demand it.
Switch to 1x1 for low-load members	A superstructure cross-member that doesn't carry much load can be 1x1 instead of 2x1.
Pocket plates and gussets	Custom gussets and mounting plates can have material removed (pocketed) in areas that aren't carrying load. Lightening pockets are free in CAD.
Use the minimum number of structural members	Every tube you add is weight. If a brace can be replaced by a gusset or the bellypan already handles the load, remove the tube.
Weigh the robot early and often	Track weight in CAD as you design. Weigh the real robot as soon as it's assembled enough to go on a scale. Finding out you're 10 lbs overweight in week 5 is much harder to fix than finding out in week 3.