Source file: docs/models/gym80-pure-kraft-45-degrees-linear-leg-press.md · rendered from the repository
gym80 4023 Pure Kraft 45 Degrees Linear Leg Press
Status: Partial – slope known, absolute value needs one measurement
Confidence of outputs: estimated · method: mechanical-model · built: 2026-10-17
Mechanism: incline sled model (starting resistance + plates × sine of the sled angle, plus rail friction)
Model
F = SR + P·sin(45°) ± friction → plate part known (0.707·P), SR unknown
Why no full numeric estimate: Starting resistance missing, so absolute values cannot be given; only the plate part of the force (P·sin θ, with its angle band) is computed – see the table in the derivation.
Inputs
| Symbol | Input | Value | Status | Uncertainty | Source (verbatim quote) |
|---|---|---|---|---|---|
| θ | Rail angle to horizontal Note: Angle taken from the official product name; we assume it is the sled travel angle. |
45 deg | ✅ sourced | ± 1 — ASSUMPTION (not sourced): ±1°; replace with inclinometer reading | manufacturer_page: “4023 PURE KRAFT 45 DEGREES LINEAR LEG PRESS” · retrieved 2026-10-17 |
| SR | Starting resistance (empty sled) Note: Not published. Only the total machine weight and the max load are stated – the sled mass is not. How to measure: Crane scale + ratchet strap, sled empty. |
— | 📏 to measure (Maxime) | — | — |
| μ | Friction coefficient How to measure: Lifting vs lowering readings. |
— | 📏 to measure (Maxime) | — | — |
| P | Plates added (label) | — | ⚙️ user setting | — | — |
⚠️ Explicit assumptions (not sourced): uncertainty band of θ. They widen the error band; they do not move the nominal value.
What can be computed now
| Plates added (kg) | Plate contribution (kgf, nominal) | Range for θ = 44°…46° |
|---|---|---|
| 20 | 14.1 | 13.9 … 14.4 |
| 40 | 28.3 | 27.8 … 28.8 |
| 60 | 42.4 | 41.7 … 43.2 |
| 80 | 56.6 | 55.6 … 57.5 |
| 100 | 70.7 | 69.5 … 71.9 |
| 140 | 99.0 | 97.3 … 100.7 |
| 200 | 141.4 | 138.9 … 143.9 |
| 300 | 212.1 | 208.4 … 215.8 |
| 400 | 282.8 | 277.9 … 287.7 |
Add the measured starting resistance SR (and friction) to get the force at the footplate. These rows are not stored as Measurements and not used by the comparator.
Validation by Maxime
Follow docs/protocole-mesure-fr.md. Geometry/ratio to measure: SR, μ. Once measured, the inputs are entered and the curve is computed with the same code (research/models/build_models.py).