Intake Design for V5RC | Spartan Design

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What an Intake Does

The intake is the mechanism that picks up game pieces from the field and moves them into the robot. Every other scoring system downstream depends on the intake working consistently.

› Intake Types › Compression › Anti-Jam › Common Mistakes › Testing Checklist

An intake must do three things: collect a game piece reliably from the floor or a stack, control it without losing it mid-motion, and hand off it to the next stage (scorer, conveyor, or shooter) without jamming. If any one of those fails, your cycle time falls apart.

🎯 Rule of Thumb

Design for the worst-case game piece, not the ideal one. Game pieces are never perfectly oriented. Rings tilt, cubes stack unevenly, balls bounce. Your intake should grab the messiest piece it will see in match conditions — not just the perfect one you tested with on a clean floor.

The Three Jobs of an Intake

Collection: Reaching out to make contact with the game piece and pulling it into the robot. This requires enough roller surface area, correct geometry relative to the piece, and motor speed matched to the approach angle.
Control: Holding the game piece securely while the robot moves, turns, or accelerates. A piece that rattles loose between collection and scoring costs you the cycle.
Handoff: Transferring the piece cleanly to whatever comes next — a conveyor, a flywheel hood, a lift channel. The transition point is where most jams happen.

💡

Intake speed vs drive speed: Your intake surface speed should generally be faster than your drive speed. If the rollers spin at the same speed the robot is driving forward, the intake is adding nothing — the game piece just rolls under it. A good starting point is intake surface speed 1.5–2× faster than drive speed at the contact point.

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Intake Types

Three main configurations. Each has a different contact geometry and works best with different game pieces and robot layouts.

Type	How It Works	Best For	Watch Out For
Side Roller	Two rollers on the left and right squeeze the game piece from the sides and pull it in	Round or oval game pieces (balls, rings); robots that need to intake while driving	Piece must be centered; if misaligned, one roller does all the work and it jams or spins the piece sideways
Top-Down Roller	One or more rollers above the piece press down and drag it backward under the robot	Discs, flat pieces, anything with a predictable top surface; works well with a ramp underneath	Compression must be tuned precisely — too light and it slips, too heavy and it stalls; needs a consistent floor surface
Conveyor / Intake Handoff	Rollers or belts pull the piece onto a moving track that carries it through the robot to the scorer	High-throughput systems; when the piece needs to travel a long distance inside the robot	More parts = more failure points; alignment along the full conveyor path must be perfect; harder to troubleshoot

Flex Wheel Choice

Flex wheels are the dominant intake wheel in modern VRC because their compliance (softness) lets them conform to game pieces with inconsistent surfaces. Hard rollers only contact the piece at a tangent line — flex wheels wrap around it, increasing contact area and grip.

Durometer (hardness): Softer = more grip and compliance, but more friction and more motor load. Start with a medium hardness and test. Too soft and the wheel deforms so much it loses efficiency.
Diameter: Larger diameter = higher surface speed at the same RPM, more contact, easier to center pieces. Smaller = faster response, fits tighter spaces.
Width: Wider contact patch = more forgiving on misaligned pieces. Use multiple wheels per axle or a wider single wheel for wide game pieces.
Spacing: On dual-roller intakes, the gap between wheels must be less than the game piece diameter — usually by 10–25% — to create positive compression. Model this in Onshape before cutting metal.

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Compression

Compression is the most important variable in intake design and the most common thing students get wrong. Too little and you drop pieces. Too much and you stall motors or break pieces.

Compression is how much the intake rollers are squeezed against the game piece relative to its natural size. If a game piece is 3.25” in diameter and your intake gap is 2.75”, you have 0.5” of compression. For flex wheels, that compression causes the wheels to deform and grip the piece.

🎯 Rule of Thumb

Start with ~10–15% compression and test from there. For a 3.25” game piece, that is 0.33–0.49” of squeeze. Run 10 intakes, count misses. Then adjust one variable at a time. If you have no misses but motors run hot, reduce compression. If you drop more than 1 in 10, increase it or slow your approach speed.

How to Set Compression Correctly

Design it in CAD first. Place the game piece model between your rollers in Onshape and measure the actual gap. Do not guess and build — that wastes an hour of rebuild time per bad guess.
Account for flex wheel deflection. The wheel compresses when loaded. The CAD gap you design for is the starting gap, not the loaded gap. Always test physically after CAD.
Test with bad piece orientations. A perfect compression setting that still fails on a tilted or dirty piece is not good enough for competition.
Check motor current under load. If your intake motors are running consistently over 2.0A during intaking, your compression is too high or your gear ratio is too slow. Either reduce compression or increase motor speed.

⚠️ Stop Building If…

Motors stall on intake
Compression is too high or motor speed too low. Fix before match day.

Pieces bounce back out
Compression too low or surface speed too slow relative to drive speed.

Intake works on the bench but not driving
Your approach speed while driving changes the dynamics. Test while moving.

One side jams more than the other
Asymmetric compression or an axle that is not square. Check geometry before adding anti-jam code.

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Anti-Jam Design & Code

Jams happen. Design your intake to minimize them mechanically first, then use code as a backup — not as a substitute for good mechanical design.

Mechanical Anti-Jam First

Chamfer or radius the entry point. Sharp corners at the intake mouth catch game pieces and cause them to wedge. Round or angle every edge that a game piece might contact on entry.
Funnel geometry. Widen the intake mouth wider than the game piece and narrow toward the rollers. This guides misaligned pieces to center rather than letting them wedge at the entry.
Smooth the handoff zone. The place where the intake passes a piece to the next stage is where most jams happen. No sharp steps, no gaps larger than half the piece diameter.
Consistent compression along the path. If compression changes partway through the intake path, pieces stall at the transition. Keep it uniform or intentionally increasing as pieces move inward.

Software Anti-Jam (Backup, Not Primary)

Current-based stall detection. Monitor intake motor current. If current spikes above a threshold for more than 100–200ms, the motor is stalling. Reverse for 250ms, then re-engage. See the Stall Detection guide for implementation.
Velocity-based detection. Monitor encoder velocity. If the motor is commanded on but velocity drops near zero, that is a stall. Same response: brief reverse, then forward.
Driver toggle. Give the driver a button to reverse the intake instantly. No complex logic — just driver awareness and a single button for manual clear.

✅

If you are adding anti-jam code before fixing the mechanical problem, you are treating the symptom. Count jams per 10 attempts. If it is more than 1, the geometry or compression needs work. Code cannot fix a fundamentally bad entry design.

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// Section 05

Common Mistakes

Every mistake on this list has cost a team a match. Learn them before you build so you recognize them before competition day.

Testing only on perfect pieces. Your practice game pieces are clean and undamaged. Competition pieces are dented, dusty, and scratched. Test on the worst pieces you can find.
Intake speed not matched to drive speed. The most common reason for dropped pieces while driving: rollers spinning at or below the robot’s forward speed. The intake can’t pull in what the robot is running past.
No funnel geometry. A square-edged intake mouth has a small acceptance window. A 30–45° angled or curved funnel doubles or triples the effective width.
Compression set on the bench, never retested while moving. Drive dynamics change the contact geometry. Always retest at match-speed approach.
Single-point contact on round pieces. If your rollers are small diameter, they contact a round piece at one point. This causes spinning and rejection. Larger diameter rollers, angled rollers, or multiple rollers along the piece solve this.
Intake arm flexes under load. A flex-wheel intake that is mounted on a flimsy arm changes compression under load. Stiffen the mount or it will work on the bench and fail in a jam.
Handoff not tested independently. Build the intake, test collection. Then separately test the handoff. Then test the full path. Isolating failure points saves hours of debugging.

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Testing Checklist & Notebook Evidence

Run every item before calling the intake competition-ready. Record every test result — that data is your notebook evidence.

🔬 Intake Testing Checklist

10 consecutive successful intakes from the floor — stationary

Record: number of misses, stalls, handoff failures

10 consecutive intakes while driving at match speed

Test at approach angle and straight-on. Count separately.

Intake from tilted and misaligned piece orientations

Tip pieces 20° off center, test 5 times each direction

Motor current measured during intake

Should stay below 2.0A sustained. Record peak and average.

Handoff to next stage tested independently

Feed pieces manually into the handoff zone and verify 0 jams in 10

Full cycle time measured: floor to scored

Time 10 cycles, record average and variance. Target <3s for most games.

Anti-jam trigger tested deliberately

Force a jam, verify auto-reverse triggers and clears within 500ms

Driver can clear manual jam with one button press

Driver practice: jam the intake, clear without stopping driving

Notebook Evidence

CAD screenshot of roller placement with compression gap labeled — shows you designed, not guessed
Data table: attempts vs. successes for each compression setting tested
Photo or video reference of worst-case piece orientations used in testing
Motor current readings at different compression settings — shows engineering tradeoff analysis
Iteration notes: what changed between version 1 and 2, and what the data showed improved
Cycle time measurement with target vs. achieved — connects directly to match scoring rate

⚙ STEMPhysics: Friction, Normal Force, and Torque

Intake design applies direct physics. Compression force is the normal force pushing the roller against the piece. Friction force = μ × normal force — so more compression increases grip up to the point where the motor torque can no longer overcome the resistance. This is why there’s an optimal compression range, not just “more is better.” Document this tradeoff explicitly in your notebook — it’s the kind of analysis that earns Expert marks on the RECF rubric.

🎤 Interview line: “We tuned our compression by measuring motor current at different gap settings. Tighter compression increased grip but crossed our motor limit at 2.3A sustained. We backed off to the point where current stayed below 1.8A with a 95% success rate — that was the optimal tradeoff.”

Related Guides

🚫

Stall Detection

Code for anti-jam and motor protection

⬆️

Lift Systems Guide

Arms, four-bars, DR4B

💨

Pneumatics Best Practices

Pneumatic actuated intakes

⚙️

Mechanism Concept Sprint

CAD your intake before cutting metal

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Intake Designfor V5RC

The Three Jobs of an Intake

Flex Wheel Choice

How to Set Compression Correctly

Mechanical Anti-Jam First

Software Anti-Jam (Backup, Not Primary)

Notebook Evidence

Related Guides

Intake Design
for V5RC