Source: https://guthlabs.ai/docs/instruments/helical-compression-extension-spring-designer/implementation/

instrument implementation / implementation-contract

# Helical Compression/Extension Spring Designer implementation

A source-bound implementation contract for Helical Compression/Extension Spring Designer; 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**: t4-293

**Effect**: Computation or source lookup only

## Input and validation requirements

The specified Wahl factor is undefined at C=1 and produces mathematically evaluable but physically nonsensical values for C<1; the instrument should enforce a valid spring-index range rather than blindly performing arithmetic. Signed-force handling is also convention-dependent.

## 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": {
    "spring_type": "compression",
    "d_mm": 2,
    "D_mm": 16,
    "N_active": 8,
    "G_MPa": 79000,
    "F_N": 100,
    "solid_height_assumption": "closed ends, total coils=N+2"
  },
  "expected_outputs": {
    "k_N_per_mm": 4.82177734375,
    "tau_MPa": 603.015343,
    "deflection_mm": 20.7392405063,
    "solid_height_mm": 20,
    "Kw": 1.1840178571
  },
  "working": "C=D/d=16/2=8. Kw=(4C-1)/(4C-4)+0.615/C=(32-1)/(32-4)+0.615/8=31/28+0.076875=1.1071428571+0.076875=1.1840178571. d^4=2^4=16 and D^3=16^3=4096. k=79000×16/(8×4096×8)=1264000/262144=4.82177734375 N/mm. τ=1.1840178571×8×100×16/(π×2^3)=1.1840178571×12800/(8π)=603.015343 MPa. δ=F/k=100/4.82177734375=20.7392405063 mm. Hs=(N+2)d=(8+2)×2=20 mm."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/helical-compression-extension-spring-designer/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/helical-compression-extension-spring-designer/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/helical-compression-extension-spring-designer/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`