Flywheel Shooters

A flywheel shooter uses one or more spinning wheels to accelerate a game piece and launch it. The flywheel stores rotational energy, and when the game piece is fed into the shooter, the wheel surface grabs it, accelerates it, and sends it out at speed. This is the most common launcher in FRC because it offers high fire rate, adjustable range through RPM control, and relatively straightforward design.

Shooter configurations

Single flywheel with hood

One powered flywheel on the bottom (or side), and a curved static surface (the "hood") on the opposite side that guides the game piece along an arc as the flywheel accelerates it.

How it works: The game piece enters between the flywheel and the hood. The flywheel grabs one side of the game piece and spins it along the curved hood. The hood's curve determines the exit angle.

Spin: Imparts backspin because one side is moving (flywheel) and the other side is stationary (hood). Backspin stabilizes the trajectory and can help the game piece "drop in" to goals at steep angles.

Best for: Ball games where backspin helps accuracy (2017, 2022, 2026). Simple, compact, and effective.

FRC examples: 254's 2017 shooter, many 2022 cargo shooters, many 2026 fuel cell shooters

Single flywheel with back rollers

Dual flywheel (top and bottom)

Hood design

The hood is the curved surface opposite the flywheel that guides the game piece through the shot. Hood geometry is one of the most important and most iterated parts of the shooter.

What the hood controls:

• Exit angle. The curve of the hood determines the direction the game piece leaves the shooter. A longer hood wraps the game piece further around the flywheel, which changes the exit angle.

• Contact time. A longer hood means the game piece contacts the flywheel for longer, which transfers more energy. But too much contact means too much friction and spin.

• Compression. The gap between the hood and the flywheel surface determines how hard the game piece is squeezed during the shot.

Fixed vs. adjustable hood:

Type	Pros	Cons
Fixed hood	Simple, reliable, no extra actuators. One shot angle, one RPM table.	Can only shoot accurately from a narrow range of distances. To hit different ranges, you change RPM only, which has limits.
Adjustable hood	Can change the exit angle for different shooting distances. Much more flexible.	More complex (needs a motor or servo), more software tuning, and the pivot adds weight and potential play.

For games that require shooting from multiple distances (like 2024), an adjustable hood is almost necessary. For games with one primary shooting location, a fixed hood is simpler and often more consistent.

Hood surface material: Low-friction material on the hood reduces spin and lets more energy go into forward velocity instead of rotation. PTFE tape (Teflon tape) on the hood backing is a common trick. Polycarbonate is also commonly used as a hood surface.

Compression

Compression in a shooter is the amount the game piece is squeezed between the flywheel and the hood (or between two flywheels).

Too little: The flywheel doesn't grip the game piece well enough. The shot is weak and inconsistent because energy transfer varies with each shot.

Too much: The game piece deforms excessively, absorbing energy and slowing the shot. The flywheel also loses more RPM per shot, which increases recovery time between shots.

Finding the right amount: Start with about 1/2" to 3/4" of compression for inflated balls. For foam rings (like 2024 notes), less compression since the game piece is thinner. Prototype and measure shot consistency at different compressions.

Flywheel sizing

Parameter	What it affects	Guidance
Wheel diameter	Larger wheels have higher surface speed at the same RPM and store more rotational energy (more inertia).	Bigger is generally better for consistency, but trades against weight and packaging. 4" is common in FRC shooters.
Wheel mass / inertia	Heavier flywheels lose less RPM per shot, meaning faster recovery and more consistent back-to-back shots.	If shots are inconsistent, add inertia (steel plates bolted to the flywheel, or a heavier wheel). Balance against spin-up time from zero.
Number of wheels	More wheels spread contact across a wider area and reduce RPM drop per shot.	Two wheels side by side on the same shaft is common. More than two gets diminishing returns.

Motors and gearing

Shooters want high RPM with enough torque to recover quickly after a shot. This is one of the few mechanisms where you use very little gear reduction (or even a speed increase).

Motor choice: Kraken X60 or NEO with no gearbox or a very low reduction (1:1 to 3:1). Some teams gear the output faster than the motor to hit higher surface speeds.

Target RPM: Your no-load flywheel speed should be 10 to 30% above your target shooting speed. This gives the PID controller headroom to maintain speed under load.

RPM recovery: After each shot, the flywheel slows down because energy was transferred to the game piece. The time to spin back up to target RPM determines your maximum fire rate. More inertia means less RPM drop per shot (faster recovery), but slower initial spin-up from zero.

The built-in encoders on Kraken and NEO motors give you direct RPM feedback for closed-loop control. The software team runs a PID or feedforward controller to hold the flywheel at a target RPM. Mechanically, your job is to make sure the flywheel and gearing are set up so the target RPM is achievable and recoverable.

Feeding the shooter

The feed system is how game pieces get from the indexer into the shooter. Inconsistent feeding is one of the most common causes of inaccurate shots, even when the shooter itself is well tuned.

Consistent entry. The game piece should enter the shooter in the same position and orientation every time. If one shot enters left-of-center and the next enters right-of-center, they'll exit at different angles.

Feed speed. Fast enough to get the game piece into the flywheel cleanly, but not so fast that it jams or bounces before the flywheel grabs it.

Sensor gating. Use a beam break or photoelectric sensor to detect when a game piece is in position, and only feed when the flywheel is at target RPM. Feeding into a flywheel that hasn't recovered produces a weak shot.

The layout sketch

1

Draw the game piece path

Sketch the game piece entering the shooter, contacting the flywheel, traveling along the hood, and exiting. Draw the game piece at several positions along this path.

2

Set flywheel and hood geometry

Position the flywheel and draw the hood curve. Check that the game piece maintains compression against both surfaces throughout its travel. The hood radius should be slightly larger than the game piece radius plus the flywheel radius so the game piece isn't crushed, but close enough to maintain contact.

3

Define the exit angle

The tangent line at the point where the game piece leaves the hood is your exit angle. Adjust hood length and curvature to hit the angle you need. An adjustable hood changes this by moving the end of the hood.

4

Add the feed path

Design the path from the indexer into the shooter. The game piece should transition smoothly from feed rollers into the flywheel contact zone with no sharp corners or gaps where the game piece can get stuck or change orientation.

Common issues and fixes

Issue	Cause	Fix
Inconsistent distance	RPM varying between shots, inconsistent feed timing, or compression varying	Check RPM recovery (add inertia or wait for recovery). Verify feed consistency with sensor gating. Check for play in hood or flywheel mounting.
Curves left or right	Flywheel not parallel to the game piece, or uneven compression across width	Check wheel alignment and hood centering. Check for wobble in the flywheel shaft or bearings.
Too much backspin (bouncing out)	Hood friction too high, or flywheel speed too fast relative to hood	Add PTFE tape to the hood. Add back rollers. Reduce flywheel speed and compensate with angle.
Not enough range	Surface speed too low or exit angle wrong	Increase RPM (check motor and gearing limits). Adjust hood angle. Use larger diameter flywheel.
Slow fire rate	Flywheel takes too long to recover	Add inertia (heavier wheel or steel plates). Add a second motor. Reduce compression slightly.
Game piece jams	Compression too high, feed speed mismatch, or gap in game piece path	Reduce compression. Match feed speed to flywheel surface speed. Smooth out transitions in the path.

Safety

A spinning flywheel stores significant energy. Never put your hand near a spinning flywheel, and never stand in the plane of the wheel (the exit path) during testing. Add polycarbonate shields around the shooter during shop testing. Use software interlocks so the flywheel only spins when the robot is enabled. When working on the shooter mechanically, verify the robot is disabled and the flywheel has fully stopped before reaching in.

Past game examples

2026 Rebuilt (fuel cells / spheres)

Fuel cells are inflated spheres launched into goals. Most competitive shooters this season use single flywheel with hood or single flywheel with back rollers. Backspin helps shots drop into the goal, but too much bounces the ball out. Many teams use adjustable hoods for multi-distance shooting.

2024 Crescendo (notes / foam rings)

Notes were large, flat foam rings. Dual flywheel configurations (top and bottom wheels) were common because the flat game piece benefited from a fast, flat trajectory with minimal spin. Adjustable hoods were important because the game rewarded shooting from many positions on the field.

2022 Rapid React (cargo / spheres)

Cargo were inflated balls shot into a central hub. Backspin control was the defining challenge because excessive spin caused balls to bounce out. Back rollers became the meta solution. Teams that dialed in spin control and RPM tables dominated.

2017 Steamworks (fuel / small spheres)

Fuel were small wiffle-ball sized spheres shot into a high boiler. High fire rate mattered because the game rewarded volume. Single flywheel with hood was common. 254's shooter is one of the best documented examples from this game.