Continuous vs. Cascade
Counterspringing is different depending on the type of stringing you use. There's a real trade at the heart of it: if you want truly accurate counterspringing, either the stringing is complex and the counterspringing is simple (cascade), or the stringing is simple and the counterspringing is complex (continuous).
Continuous stringing is much more common in competition robotics, so most of this site's examples lead with it — but every method page covers both.
The two architectures, side by side
Stage motion — continuous stringing
Moving mass (illustrative)
Stages engage one after another, so the moving mass — and the force the counterspring must match — increases in steps.
In a continuous lift, the string routes so that stages extend one after another, typically from the inside out. Only part of the lift is moving at any moment; each stage that engages adds its mass to the moving set.
- Stage motion: sequential — stage 1 tops out, then stage 2 begins, and so on.
- Moving mass: increases in steps as the lift extends.
- Load on the counterspring: stepped — low at the start, building to the full moving weight.
- Stringing: simple to rig and maintain; the most common approach.
Stage motion — cascade stringing
Moving mass (illustrative)
Every stage moves for the entire stroke, so the load on the actuation point stays roughly constant.
In a cascade lift, the string is rigged so that all stages extend simultaneously, each stage moving proportionally faster than the one below it. The whole moving mass is in motion for the entire stroke.
- Stage motion: simultaneous — everything moves together, outer stages fastest.
- Moving mass: constant — every stage moves for the whole stroke.
- Load on the counterspring: roughly constant at the actuation point (and multiplied by the rigging ratio).
- Stringing: more complex to rig; each stage needs its own pulley run, and the actuation sees higher force over less string travel.
Why moving mass changes the required force
On a typical continuous lift the motor's load grows as the lift extends: at first only the carriage moves, then a slide stage joins it, then another. The gravity force at any extension is the weight of whatever is currently moving.
In plain terms: The force gravity exerts along the lift equals the mass currently in motion, times gravitational acceleration, reduced by the lift's angle from vertical travel (a lift tilted from vertical carries less of its weight along the slide axis).
Assumes: Rigid stages · Friction ignored · Quasi-static (no acceleration term)
A cascade lift has no such staircase — the moving mass is the whole lift for the entire stroke, so the gravity load at the actuation point stays roughly constant (the rigging also multiplies force and divides travel, which is why cascade needs stronger actuation).
What this means for each method
Because continuous lifts present a stepped load and cascade lifts a constant one, the same spring behaves very differently on each:
| Method | On a continuous lift | On a cascade lift |
|---|---|---|
| Bungee | Linear force vs. stepped load — matches at one or two points only | Linear force vs. constant load — pretension-dominant setups match better |
| Constant force | Excellent: one spring rating per stage tracks the staircase | Workable: a single rating offsets the constant load |
| Constant torque | One force level can't track the staircase | Good match for the constant load at the winch |
| Sprung linkage | Hardest target: geometry must approximate steps | Easiest target: a near-constant profile |
Not sure which you have?
Trace one string from the motor spool to the carriage:
- If the string passes over a pulley on each moving stage and anchors back near the base repeatedly, it's cascade.
- If each stage is pulled by the stage below it (string or belt segment per stage, engaging in order), it's continuous.
- If the lift only has one moving stage, the distinction disappears — treat it as a single-stage continuous lift; every method's "continuous" tab applies.
Which should you build?
Everything above is about reading the lift you have. If the lift doesn't exist yet, the architecture is still a choice you get to make — and this site takes a position on it.
Next: work through what your team has to weigh before picking a method, in the Selection Considerations.