Elevators
An elevator moves a mechanism in a straight line, typically vertically. Games frequently require scoring at different heights, which makes elevators one of the most common subsystems in FRC. Elevators are classified by how they're rigged, which determines how motor power translates to carriage travel.
Structure basics
Most FRC elevators are built from 2x1 or 1x1 aluminum box tube. Each stage is a rectangular frame that slides inside the next larger stage, guided by bearing blocks bolted to the tubes. The innermost stage holds the carriage (the platform that carries your mechanism), and the outermost stage is the base, bolted to the robot frame.
Bearing blocks are what make the stages slide smoothly. They bolt to one stage and ride on the tube of the adjacent stage. WCP sells inline bearing blocks (which fit between tubes for a minimal 1/4" gap between stages) and face-clamping blocks. The bearing block choice determines the gap between stages, which affects the overall width of the elevator.
Rigging types
Rigging is what transmits motor power to each stage. The two rigging types produce fundamentally different motion, and the choice affects speed, controllability, and complexity.
In a continuous elevator, the carriage (innermost stage) moves first. Once it reaches the top of its travel within its parent stage, the next stage starts moving. The stages extend sequentially, not simultaneously. The carriage always moves at 1:1 with the motor output regardless of how many stages you have.
How the rigging works: A belt (or rope) runs from a powered spool or drum, through a path of pulleys at the top and bottom of each stage, and attaches to the carriage. A second belt/rope does the same on the retract side. The belt snakes through all the stages in one continuous loop. When the motor drives the belt, the carriage moves directly.
Belt-in-tube continuous is the competitive standard. The belt runs inside the box tube of each stage, which keeps the rigging protected, compact, and clean. The belt doesn't need external tensioning because it's constrained by the tube and pulleys. This is what the top-tier elevator teams are running.
Rope and pulley continuous is the other approach. Dyneema rope runs over pulleys at the top and bottom of each stage. This works but requires more careful tensioning and the rope path is more complex to set up.
Advantages:
Direct 1:1 relationship between motor and carriage makes control precise and predictable
No speed or current multiplication (motor sees the actual carriage load directly)
Belt-in-tube rigging is clean, enclosed, and doesn't need external tensioners
Lower center of gravity at partial extension because only the inner stages move first
Disadvantages:
Harder to design and implement than cascade (the belt/rope path through all stages is complex)
Carriage speed is limited to 1x motor output speed (no mechanical speed advantage)
If the belt/rope breaks anywhere in the continuous path, the entire elevator loses power
FRC examples: 3847 Spectrum's 2023 belt-driven continuous, 4414's 2023 continuous, 111 Wildstang's belt-in-tube 3-stage, 4522 Team SCREAM's belt-in-tube 2-stage
In a cascade elevator, all stages move simultaneously. When the motor drives the first stage up, rope or chain loops pull each subsequent stage up relative to the one below it. The result is that the carriage moves at a multiple of the motor's output speed (2x for 2-stage, 3x for 3-stage).
How the rigging works: The motor drives the first stage directly (usually with chain or belt). A loop of Dyneema rope connects each pair of adjacent stages: one end fixed to the outer stage's frame, the rope goes over a pulley at the top of the outer stage, and the other end attaches to the inner stage. When the outer stage rises, the rope pulls the inner stage up at the same rate.
Rigging materials:
Chain (#25) for the motor-driven first stage. Strong and doesn't stretch.
Dyneema rope for the passive stage-to-stage loops. Lightweight, strong, and doesn't stretch meaningfully.
Belt as an alternative to chain for the first stage.
Advantages:
Simpler to understand, design, and build than continuous
All stages extend together, so the elevator is fast (carriage speed is multiplied by stage count)
The cascade acts as a mechanical advantage, so the motor sees a fraction of the carriage load
Easier to learn on. If the team hasn't built an elevator before, cascade is the safer choice.
Disadvantages:
Speed multiplication means you need to gear the motor slower to maintain controllability
Current draw is also multiplied for a given carriage load
Rigging Dyneema loops between stages requires tensioning at each stage pair
Higher center of gravity at partial extension because all stages are partially extended
FRC examples: 2468's 2023 cascade, 177's 2025 3-stage cascade, ThriftyBot elevator kit (cascade option), WCP GreyT elevator
How to choose
Carriage speed
1:1 with motor (need a fast motor/ratio)
Multiplied by stage count (fast even with slower motor)
Control precision
Excellent (linear, predictable)
Good but requires accounting for speed multiplication
Motor load
Full carriage weight on motor
Divided by stage count
Rigging complexity
Higher (continuous belt path through all stages)
Lower (separate loop per stage pair)
Tensioning
Minimal with belt-in-tube
Needs tensioning on each Dyneema loop
Competitive level
The premium choice. Most top-tier elevators are continuous belt-in-tube.
Proven and reliable. Easier to implement and debug.
Our recommendation: We have used cascade on 4123 in the past and recommend it for teams building their first elevator. It's simpler to implement, easier to debug, and there are excellent COTS kits (ThriftyBot, WCP GreyT) that give you a starting point. If the team wants to push for the most competitive option, continuous belt-in-tube is where the meta is, but it's a harder design and build.
Counterbalancing
An elevator fighting gravity to lift a carriage, end effector, and game piece draws a lot of current, makes control harder, and risks the carriage crashing down if the motor loses power. A counterbalance offsets the carriage weight so the motor only needs to produce force for acceleration and deceleration, not for holding against gravity.
Constant force springs are the standard. A constant force spring is a coiled strip of spring steel that produces roughly the same force regardless of how far it's extended. One end attaches to the base stage, the other to the carriage or final stage.
Constant force spring
The standard. Consistent force across full range of travel. Available from McMaster in various force ratings. Select a total force that offsets most of the carriage weight.
Surgical tubing / bungee
Cheaper and easier to source, but force increases as the elastic stretches. Weakest at the bottom (where you need it most), strongest at the top (where you need it least). Works in a pinch but not ideal.
Gas spring
Consistent force, compact, not adjustable without swapping.
Size the counterbalance to near-zero net load, not to overpower gravity. If the spring force is stronger than the carriage weight, the elevator will want to extend on its own and the motor has to fight it coming down. Aim for roughly equal motor current draw going up and going down.
How to size: Weigh the carriage with everything on it (mechanism, wiring, game piece). For cascade, the spring force needs to offset the weight divided by the cascade mechanical advantage. For continuous, it offsets the full weight directly. Use ReCalc to verify the motor handles the remaining load.
Tensioning
One of the biggest advantages of belt-in-tube continuous rigging is that the belt generally doesn't need external tensioning. The belt is constrained by the tube and the pulleys at the top and bottom of each stage. Once installed at the correct length, it stays taut.
If you do need to adjust, some teams add a small idler or adjustment point at one end of the belt path.
Tension chain the same way you would any chain run on the robot: slotted mounting holes on the motor or a cam tensioner on the drive shaft.
Dyneema needs to be tight when installed. Tie or clamp the rope to anchor points with the elevator fully retracted, pull tight by hand, and secure.
Many teams use a tensioning spool (a small hex shaft with rope wrapped around it, turned with a wrench) to fine-tune tension. The ThriftyBot and WCP GreyT elevator kits both use this approach. Check tension after the first few operation cycles because rope can settle slightly.
Check rigging tension before every competition and after every significant impact. An elevator that's been hit hard can shift enough to introduce slack, and slack on a cascade can cause stages to drop suddenly on direction reversal.
Motors, gearing, and mounting
Elevators need high torque at moderate speed. Two Kraken X60s on a shared gearbox is a common setup for competition elevators.
Gearing for cascade: The cascade multiplies effective speed and divides effective force. A 3-stage cascade at 9:1 motor reduction means the carriage moves at 3x the first-stage speed. Use ReCalc with the cascade multiplier: set effective load to carriage weight divided by stage count, and effective speed to target carriage speed divided by stage count.
Gearing for continuous: No speed multiplication. Gear based on the full carriage weight and target carriage speed directly.
Mount your motor and gearbox solidly. The motor shaft and gearbox need to be rigidly supported where they connect to the elevator drive shaft. If there is any flex or play in the motor mount, the drive shaft will deflect under load and the whole elevator will have problems: binding, inconsistent motion, and accelerated bearing wear. We learned this the hard way in 2025 when insufficient motor mounting caused persistent elevator issues throughout the season. Bolt the gearbox to a rigid plate, support the output shaft at both ends with bearings, and make sure nothing can flex.
Common issues
Carriage drops when motor is off
No counterbalance, or counterbalance too weak
Add or increase constant force spring. Verify motor is in brake mode when stopped.
Elevator jerks or skips
Slack in rigging, worn chain, or bearing blocks too loose
Retension rigging. Replace worn chain. Adjust bearing blocks for smooth slide with minimal play.
Stages bind or stick
Bearing blocks too tight, stages not parallel, debris in bearing track
Loosen blocks slightly. Check tube straightness and parallelism. Clean bearing surfaces.
Motor draws excessive current
No counterbalance, or gear ratio too aggressive
Add counterbalance. Use a higher reduction.
Carriage overshoots position
Moving too fast for software to control
Add encoder to drive shaft. Use motion profiling. For cascade, verify gearing accounts for speed multiplication.
Elevator feels sloppy or wobbly
Motor/gearbox mount has flex, or output shaft unsupported
Rigidly mount the gearbox. Support the drive shaft at both ends. Check for any play in the drivetrain.
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