Conveyor Types
Once the intake grabs a game piece, it needs to get from the intake to the scoring mechanism (shooter, gripper, placer). The path between those two points is the conveyor or indexer. The conveyor's job is to move game pieces through the robot reliably, in the right order, at the right speed, and to deliver them to the scoring mechanism in a consistent position and orientation every time.
A bad conveyor is one of the most common reasons an otherwise good robot has inconsistent scoring. The intake works, the shooter works, but game pieces get stuck or arrive at the shooter at different angles, and shots go everywhere.
Conveyor types
Multiple strands of round elastic cord (polycord) running in parallel between two shafts. The game piece rides on top of the polycord strands (horizontal conveyor) or is squeezed between polycord and a wall (vertical conveyor).
How it works: Two hex shafts with grooved hubs at each end. Polycord loops stretch between matching grooves on the two shafts. One shaft is powered by a motor, the other spins freely. The polycord strands move like a conveyor belt, carrying the game piece along.
Key details:
Space the polycord strands so the game piece rides on top of them without falling through the gaps
The gaps between strands let debris fall through rather than accumulating
Polycord provides moderate grip. For more grip, add more strands or use thicker cord
Tension each strand consistently. Uneven tension causes the game piece to track to one side.
Common cord diameters: 3/16" and 1/4"
Best for: Moving multiple game pieces in sequence (ball games with hoppers), horizontal or slightly angled transport paths. Very common in shooter-based robots where the conveyor feeds balls from a hopper to the shooter.
FRC examples: 254's 2017 hopper conveyor, many 2022 and 2026 ball transport systems
A series of powered rollers that the game piece rolls across. Each roller is a tube (polycarb or with grip tape) spinning on its own shaft, and the game piece moves by contacting the top of each roller in sequence.
How it works: Multiple rollers are mounted in a row. They're all driven by a shared belt, chain, or by meshing with each other. The game piece sits on top of the rollers, and the spinning surfaces push it along the path.
Key details:
Roller spacing must be close enough that the game piece always contacts at least two rollers simultaneously, or it will sag between rollers and get stuck
All rollers need to spin at the same speed (use a shared drive belt or chain) or the game piece will rotate or jam
Grip tape on the rollers improves contact with the game piece
Rollers can handle heavier game pieces better than polycord because the load is distributed across rigid cylinders
Best for: Larger or heavier game pieces that need solid support underneath, or paths where the game piece needs to maintain a specific orientation while being transported.
A continuous flat belt stretched between two rollers, with the game piece riding on the belt surface.
How it works: A flat belt (or wide timing belt) loops around two rollers. One roller is powered, the other is an idler. The belt surface moves the game piece by friction. The belt can be horizontal, angled, or even vertical if the game piece is compressed between the belt and a wall.
Key details:
The belt needs enough tension to not slip on the drive roller but not so much that it adds excessive load on the motor
A flat belt provides continuous surface contact, which gives more consistent piece transport than polycord (no gaps between strands)
The belt surface can be augmented with grip tape or textured material for more traction
Flat belts are harder to source and tension than polycord, and they're wider, which takes more space
Best for: Situations where polycord gaps cause problems (very small game pieces, or pieces that need continuous support). Also useful for vertical lifts where the piece needs to be squeezed between two opposing belts.
FRC examples: Some 2017 and 2022 vertical feeders, 469's 2012 vertical belt conveyor
A row of wheels or compliant wheels mounted on a shared shaft or plate. The game piece rolls across the wheel surfaces. Sometimes called a "roller bar" or "wheel wall."
How it works: Wheels (often compliant wheels or flex wheels) are mounted in a line. They can be on a single shared shaft (all spinning together) or on individual axles. The game piece contacts the wheels and gets pushed along. Often used as one side of a conveyor path, with a wall or another wheel series on the opposite side providing compression.
Key details:
Compliant wheels conform to the game piece, which provides better grip than rigid surfaces
A single shared hex shaft with flex wheels stacked on it is the simplest version to build
Useful for both horizontal transport and vertical lifts (game piece squeezed between two wheel walls)
Wheel spacing and compression are game-piece-dependent and need to be prototyped
Best for: Compact paths where you need high grip and conformability. Very common as the "walls" of a vertical feeder channel where the game piece is squeezed between two opposing sets of powered wheels.
No powered conveyor at all. The game piece moves through the robot under gravity, guided by chutes, ramps, or funnels.
How it works: The internal path is sloped so game pieces slide or roll from the intake to the scoring mechanism. Polycarb or aluminum sheet forms the chute walls. The geometry controls direction and speed.
Key details:
The slope needs to be steep enough that the game piece actually moves, accounting for friction between the piece and the chute surface
Use low-friction materials (polycarbonate, PTFE tape) on chute surfaces
The chute needs to funnel the game piece into the correct position and orientation for scoring
Game pieces can get stuck at transitions, corners, or flat spots in the chute
Advantages: Zero motors, zero weight, zero complexity. The game piece just falls.
Disadvantages: No active control over timing or speed. Pieces can jam, especially if they're soft or irregular shaped. Can't move pieces upward.
Best for: Situations where the intake feeds directly into a hopper above the scoring mechanism, and gravity naturally moves pieces to where they need to go. Works best with rigid, round game pieces that roll predictably.
Choosing the right conveyor
Grip
Medium
Medium to high
Medium
High (compliant wheels)
N/A
Piece support
Gaps between strands
Solid per roller, gaps between
Continuous
Per wheel, gaps between
Continuous (chute surface)
Complexity
Low
Moderate
Moderate
Low to moderate
Very low
Weight
Light
Moderate
Moderate
Light
Lightest
Direction
Horizontal, slight angle
Horizontal, slight angle
Any (including vertical)
Any (including vertical)
Downward only
Best for
Ball hoppers, multi-piece transport
Heavy pieces, orientation control
Vertical lifts, continuous support
Compact feeder channels
Simple paths, rigid round pieces
Indexing
Indexing means controlling when and where game pieces move through the conveyor. Without indexing, pieces pile up, feed into the shooter at random times, and cause jams. With indexing, you control the flow: one piece at a time, delivered exactly when the scoring mechanism is ready.
How to index:
Place a beam break sensor at the position where you want the game piece to wait (usually just before the scoring mechanism)
The conveyor runs until the beam break detects a piece at the holding position, then stops
When the scoring mechanism is ready (flywheel at target RPM, arm in position), the conveyor feeds the piece forward
A second beam break at the exit confirms the piece has left
Single piece indexing is the simplest case: the conveyor holds one piece at the ready position and feeds it when commanded. This is appropriate when the robot only holds one game piece at a time.
Multi-piece indexing (serialization) is needed when the robot holds multiple pieces (like a hopper of balls). The conveyor feeds pieces one at a time from the hopper to the shooter, with sensor gating controlling the spacing so pieces don't bunch up and double-feed.
Sensor-gated feeding is the single biggest improvement you can make to scoring consistency. Even if the conveyor and shooter are well-built, feeding a game piece into a shooter that hasn't recovered RPM from the last shot, or feeding two pieces at once, ruins accuracy. Gate every feed with a sensor.
The game piece path
Design the entire path from intake to scoring mechanism as one continuous system, not as separate mechanisms bolted together.
Map the path in the layout sketch
Draw the game piece at every stage: on the ground, entering the intake, clearing the bumper, entering the conveyor, traveling through the conveyor, arriving at the holding position, and entering the scoring mechanism. This is one continuous line through the robot.
Eliminate dead spots
A dead spot is anywhere the game piece loses contact with a powered surface or gets stuck in a transition. These happen where the intake hands off to the conveyor, where the conveyor changes direction, or where the conveyor feeds into the shooter. Every transition should have continuous powered contact.
Match speeds at handoffs
Where one powered surface hands off to the next (intake rollers to conveyor, conveyor to shooter feed), the surface speeds should be close. If the intake runs at 2x the conveyor speed, the game piece slams into the slower conveyor and jams. If the conveyor runs faster than the shooter feed, pieces pile up at the transition.
Add sensors at key positions
At minimum: one sensor at the holding position (before the scorer) to gate feeding. Better: an additional sensor near the intake to detect when a piece has been acquired. Best: sensors at every holding position along the path for full software control of piece flow.
Common issues
Game pieces jam at transitions
Speed mismatch between adjacent conveyors, dead spot where no surface contacts the piece, or geometry forces the piece to change direction too sharply
Match surface speeds at every handoff. Ensure continuous contact through transitions. Smooth out sharp corners with polycarbonate guides.
Pieces arrive at scorer in wrong orientation
The conveyor path doesn't constrain the piece's rotation, or a transition allows the piece to spin
Add guide walls that prevent rotation. Narrow the conveyor channel to match the piece's intended orientation.
Double feeding
No sensor gating, or sensor positioned wrong so it doesn't detect closely spaced pieces
Add a beam break at the holding position. Verify the sensor detects the trailing edge of one piece before allowing the next to feed.
Pieces fall out of the robot
Open gaps in the conveyor path, or the piece bounces at a transition
Close up gaps with polycarb panels. Add guards at transitions where pieces might bounce.
Conveyor is too slow
Motor undergeared, polycord slipping on the hub, or too much friction in the path
Check motor and gearing (conveyors are low-torque, high-speed applications). Verify polycord tension. Reduce friction with smoother guide surfaces.
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