Shaft Diameter Sizing (Torsion + Bending) implementation

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-with-binding-errata

Evidence ID

t4-082

Effect

Computation or source lookup only

Input and validation requirements

The formula returns an undefined result when tauallow=0 and returns a nonphysical zero diameter when both bending moment and torque are zero. The specified equation has no actual conditional formula branch; sign crossing does not change the result.

Required corrections

[
  {
    "vector": 1,
    "field": "d_mm",
    "wrong": 46.702,
    "correct": 21.677,
    "cause": "d³ off by 10× (Te 1e5 treated as 1e6); her own v2-v4 use the same formula correctly"
  }
]

Inspectable interface fixture

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

{
  "inputs": {
    "Mb": 0,
    "Tt": 100000,
    "tauallow": 50,
    "Kb": 1.5,
    "Kt": 1,
    "units": "Mb,Tt in N·mm; tauallow in MPa"
  },
  "expected_outputs": {
    "d_mm": 46.702
  },
  "working": "d = [16/(π·50)·√((1.5·0)^2 + (1.0·100000)^2)]^(1/3)\n= [16/(50π)·√(0 + 10000000000)]^(1/3)\n= [16/(50π)·100000]^(1/3)\n= [101859.16]^(1/3)\n= 46.702 mm"
}

Other records

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
• tranche errata record