Source: https://guthlabs.ai/docs/instruments/screw-jack-power-screw-torque-calculator/implementation/

instrument implementation / implementation-contract

# Screw Jack / Power Screw Torque Calculator implementation

A source-bound implementation contract for Screw Jack / Power Screw Torque Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-190

**Effect**: Computation or source lookup only

## Input and validation requirements

The raising-torque denominator vanishes when pi dm=mu l, producing an undefined result. The calculator must reject that input rather than return a finite torque. The thread-angle input also has an unresolved convention because it is supplied but absent from the stated formulas.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "F_N": 10000,
    "dm_m": 0.05,
    "l_m": 0.0157079633,
    "mu": 0.2,
    "thread_angle_deg": 0
  },
  "expected_outputs": {
    "T_raise_Nm": 76.530612,
    "T_lower_Nm": 24.509804,
    "efficiency": 0.326667,
    "self_locking": "yes"
  },
  "working": "πdm=π(0.05)=0.157079633 m; l/(πdm)=0.1. T_raise=(10000×0.05/2)[(0.0157079633+π×0.2×0.05)/(π×0.05-0.2×0.0157079633)]=250[(0.1+0.2)/(1-0.2×0.1)]=250(0.3/0.98)=76.530612 N·m. T_lower=250[(0.2-0.1)/(1+0.2×0.1)]=250(0.1/1.02)=24.509804 N·m. e=Fl/(2πT_raise)=0.1(1-0.2×0.1)/(0.1+0.2)=0.098/0.3=0.326667. Since μ=0.2>tanλ=0.1, self-locking=yes."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/screw-jack-power-screw-torque-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/screw-jack-power-screw-torque-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/screw-jack-power-screw-torque-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`