Climber Archetypes
Almost every FRC game since 2016 has included an endgame climbing task. The specific challenge changes (bars, chains, cages, ropes, ramps), but the underlying mechanisms fall into a handful of archetypes that get adapted season to season. Understanding these archetypes means that when a new game is revealed, you can quickly identify which climbing approach fits the field element rather than starting from scratch.
The archetypes
A tube-in-tube telescoping arm extends upward, a hook at the top grabs the climbing structure, and a winch at the base pulls the robot up by reeling in rope or cable.
How it works: Constant force springs (or gravity, depending on orientation) extend the telescoping tubes upward. The hook at the top engages the bar, chain, or cage. A motor on a high-reduction gearbox spins a spool that winds Dyneema rope, pulling the robot's frame up toward the hook.
Extend mechanism: Constant force springs are the standard. They push the tubes out with a consistent force. When the winch reels in, it overpowers the springs and the arm retracts, lifting the robot. Some teams use motors to extend instead of springs.
Key design details:
The hook needs to passively engage the climbing structure (latches on contact) or be actuated to close
The winch spool needs enough wraps of rope to cover the full travel distance
A ratchet on the winch prevents the rope from unspooling if the motor loses power (critical for staying climbed)
The telescoping tubes need bearing blocks to slide smoothly, same concept as elevator stages
COTS options: AndyMark's Climber in a Box is a complete kit that implements this archetype. It's well tested and a solid starting point if the team doesn't want to design a climber from scratch.
Used in: 2020/2021 Infinite Recharge (bar), 2024 Crescendo (chain), 2026 Rebuilt (cage). This is the most common climbing archetype across recent FRC games.
FRC examples: 254's telescoping climbers, 2056's designs (both inspired the Climber in a Box kit)
An arm on a pivot rotates upward, hooks onto the climbing structure, and then the arm retracts (or the pivot pulls the robot up) to complete the climb.
How it works: A motor-driven arm pivots from a stowed position (inside frame perimeter) to an extended position where the hook reaches the climbing structure. The hook engages, and then the arm pivots back or a winch pulls the robot up.
Key design details:
The arm pivot needs to handle the full weight of the robot, so it requires high gear reduction and a dead axle pivot (see the Arms and Pivots page)
The hook geometry needs to match the specific climbing structure for the season
Some designs use the arm pivot itself to lift the robot (the motor pulls the arm back after hooking). Others use the arm just to place the hook and then a separate winch does the lifting.
A ratchet or brake is essential so the arm doesn't back-drive under the robot's weight
Advantages over telescoping: Can be simpler if the team already has an arm on the robot that can double as a climber. Fewer linear motion components (no bearing blocks or telescoping tubes).
Disadvantages: The arc path of a pivoting arm may not align well with every climbing structure. Harder to reach directly above the robot compared to a vertical telescope.
Used in: 2023 Charged Up (bar), 2025 Reefscape (cage), various seasons where an existing arm could be repurposed
The robot's elevator reaches up, hooks onto or braces against the climbing structure, and then the elevator retracts to lift the robot.
How it works: The elevator extends the carriage upward. A hook or brace on the carriage engages the climbing structure. The elevator motor reverses and pulls the robot frame up toward the carriage.
Key design details:
The elevator needs to be strong enough to support the robot's full weight in tension (pulling the frame up), not just compression (pushing the carriage up). Some elevator designs that work great for lifting game pieces will fail under climbing loads because the forces reverse direction.
The rigging and bearing blocks must handle the reversed loading without binding
A ratchet or mechanical lock is needed to hold the robot in the climbed position
Advantages: If the robot already has an elevator for scoring, repurposing it for climbing saves weight and mechanism count. One mechanism, two jobs.
Disadvantages: The elevator has to be designed from the start to handle climbing loads. Retrofitting a scoring-only elevator into a climber is risky. The elevator also needs to reach high enough to engage the climbing structure, which may require more stages than scoring alone would need.
Used in: 2023 Charged Up (many teams used their elevator to climb), 2025 Reefscape (cage climb)
The robot drives onto or against a ramp structure (either on the field or deployed by the robot) and gravity or friction holds it in place.
How it works: Some games include field ramps that robots drive onto for endgame points. Others allow robots to deploy their own ramp-like mechanisms. The "climb" is just driving to the right position and stopping.
Key design details:
For field ramps: the drivetrain needs enough traction and power to drive up the incline
For deployed ramps: the mechanism needs to be stowed during the match and deployed quickly in endgame
Braking (putting the drivetrain in brake mode) is usually sufficient to hold position on a ramp
Advantages: Extremely simple mechanically. No hooks, no winches, no ratchets.
Disadvantages: Only works when the game provides a ramp or the scoring doesn't require lifting off the ground. Most modern FRC endgames require actually lifting the robot, which ramps can't do.
Used in: 2018 Power Up (scale platform), some games with tiered platforms. Less common in recent seasons where hanging from a bar or cage is required.
Common components across all climbers
Regardless of which archetype you use, most climbers share these design elements:
Hook
Engages the climbing structure (bar, chain, cage)
Shape and size are game-specific. Must hold the robot's full weight. Usually steel or thick aluminum.
Ratchet or mechanical lock
Prevents back-driving so the robot stays climbed
A ratchet on the winch spool or arm shaft. WCP sells ratchet plates. Some teams use worm gear reductions that are naturally non-backdrivable.
High-reduction gearbox
Provides enough torque to lift the full robot weight
The climber motor is lifting 120+ lbs. Typical reductions are 50:1 to 150:1 depending on spool diameter and mechanism type.
Rope (Dyneema)
Connects the hook to the winch spool
Dyneema is the standard. Lightweight, doesn't stretch, absurdly strong for its diameter. 2mm or 3mm Dyneema handles FRC climbing loads easily.
Constant force springs
Extends the climber passively
Used in telescoping designs to push the tubes out. Sized to extend the mechanism but not so strong that the winch struggles to overcome them.
Dual-purpose mechanisms
The best climbers are often mechanisms that already exist on the robot for another purpose. If your elevator, arm, or telescoping mechanism can also hook onto the climbing structure, you save weight and complexity by not building a dedicated climber.
Questions to ask during strategy:
Can our elevator reach the climbing structure? If so, can we add a hook to the carriage and climb with the elevator?
Can our arm pivot high enough to hook the bar? If so, can the arm motor handle the climbing load?
Can we add a small hook mechanism to an existing structure (like the top of the elevator) with minimal additional weight?
If the answer to any of these is yes, it's almost always better to adapt the existing mechanism than to build a separate climber. A dedicated climber that only gets used in the last 20 seconds of a match is a lot of weight and design time for a mechanism that sits idle for 2 minutes and 10 seconds.
Sizing the winch
If your climber uses a winch (most do), here's how to size it:
Determine the lift distance
Measure from where the hook engages the climbing structure to how high the robot's belly needs to be off the ground to score full climb points. That distance plus some margin is the total rope your spool needs to wind.
Pick a spool diameter
A smaller spool means more wraps of rope for the same distance (more motor rotations, slower climb, but higher force). A larger spool means fewer wraps (fewer rotations, faster climb, but the motor needs more torque). Common spool diameters are 1" to 2".
Calculate gearing
Use ReCalc with a linear mechanism setup. Input the robot weight as the load, the spool diameter as the drum size, and your desired climb time. The calculator will tell you what gear ratio and motor configuration you need. Most climbs target 3 to 8 seconds.
Verify current draw
Make sure the motor current during the climb is within safe limits. Climbing draws high current because you're lifting the full robot weight. If the current is too high, increase the gear reduction (slower but less current) or add a second motor.
Reliability
The climber is the mechanism most likely to be needed in a close match and least likely to have been thoroughly tested because it only runs in the last 20 seconds. Build reliability into the design:
Test the climber 50+ times before competition. Not 5 times. Not 10 times. Fifty. You need to find the failure mode before it finds you in eliminations.
Use a ratchet or worm gear so the robot can't fall. A robot falling off a climbing structure during a match is dangerous and results in penalties.
Make the hook engagement dead simple for the driver. The driver is stressed, there are 15 seconds left, and they need to line up the hook. If the engagement requires perfect alignment, it will fail when it matters most. Design the hook with generous funneling so it catches even if the driver is off by an inch or two.
Keep the climber independent from other mechanisms. If climbing requires retracting the intake and stowing the arm and extending the climber in a specific sequence, something will go wrong. The fewer dependencies the climb has on other mechanisms, the more reliable it will be.
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