Source: https://guthlabs.ai/docs/instruments/gear-ratio-rpm-speed-calculator/implementation/

instrument implementation / implementation-contract

# Gear Ratio / RPM-Speed Calculator implementation

A source-bound implementation contract for Gear Ratio / RPM-Speed 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**: t4-139

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero gear ratio creates an undefined division, and an unspecified tire-diameter unit can change the calculated speed by a factor of 12.

## 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": {
    "mode": "speed_at_rpm",
    "rpm": 3000,
    "gear_ratio": 3.5,
    "final_drive": 3.73,
    "tire_diameter_in": 26
  },
  "expected_outputs": {
    "speed_mph": 17.7748
  },
  "working": "Convert diameter: 26 in ÷ 12 = 2.1666667 ft. Circumference = π × 2.1666667 = 6.8067841 ft. Speed = (3000 × 6.8067841 × 60) ÷ (3.5 × 3.73 × 5280) = 1,225,221.1349 ÷ 68,930.4 = 17.7748 mph."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/gear-ratio-rpm-speed-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/gear-ratio-rpm-speed-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/gear-ratio-rpm-speed-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`