{
  "tool": "piston-ring-end-gap-calculator",
  "version": "1.0.0",
  "author": "bryan-terry",
  "location": "Van Buren, Arkansas",
  "date": "2026-07-17",
  "description": "Calculates piston ring end gap accounting for thermal expansion differential between block and piston materials",
  "formulas": {
    "baseline_gap": {
      "expression": "Gap_0 = k × D_bore",
      "variables": {
        "k": "clearance_coefficient_inches_per_inch",
        "D_bore": "bore_diameter_inches"
      },
      "units": "inches"
    },
    "thermal_closure": {
      "expression": "ΔGap_T = D_bore × (α_block − α_piston) × ΔT",
      "variables": {
        "D_bore": "bore_diameter_inches",
        "alpha_block": "thermal_expansion_coefficient_block_per_Celsius",
        "alpha_piston": "thermal_expansion_coefficient_piston_per_Celsius",
        "delta_T": "temperature_rise_Celsius"
      },
      "units": "inches"
    },
    "operating_gap": {
      "expression": "Gap_op = Gap_0 − ΔGap_T",
      "units": "inches"
    }
  },
  "constants": {
    "clearance_coefficients": {
      "cast-iron": {
        "value": 0.004,
        "unit": "inches_gap_per_inch_bore",
        "source": "Standard automotive practice, Ford Small Block Service Manual 1965"
      },
      "aluminum": {
        "value": 0.003,
        "unit": "inches_gap_per_inch_bore",
        "source": "High-performance aluminum piston specification, Wiseco Engineering Handbook"
      },
      "steel": {
        "value": 0.0035,
        "unit": "inches_gap_per_inch_bore",
        "source": "Industrial diesel piston specification, Caterpillar Service Manual"
      }
    },
    "thermal_expansion_coefficients": {
      "cast-iron": {
        "value": 11e-6,
        "unit": "per_Celsius",
        "source": "MatWeb ASTM A48 Class 30 Gray Iron"
      },
      "aluminum": {
        "value": 23e-6,
        "unit": "per_Celsius",
        "source": "MatWeb AA319 Aluminum Casting Alloy"
      },
      "steel": {
        "value": 12e-6,
        "unit": "per_Celsius",
        "source": "MatWeb AISI 1020 Carbon Steel"
      }
    }
  },
  "validation_rules": {
    "seize_risk": {
      "condition": "operating_gap <= 0",
      "action": "REJECT_ASSEMBLY"
    },
    "marginal_reserve": {
      "condition": "operating_gap < (baseline_gap × 0.3)",
      "action": "WARN_INSUFFICIENT_CLEARANCE"
    },
    "safe_operation": {
      "condition": "operating_gap >= (baseline_gap × 0.3)",
      "action": "APPROVE_ASSEMBLY"
    }
  },
  "worked_example": {
    "inputs": {
      "bore_inches": 4.0,
      "block_material": "cast-iron",
      "piston_material": "aluminum",
      "delta_T_Celsius": 180
    },
    "outputs": {
      "baseline_gap_inches": 0.012,
      "thermal_closure_inches": -0.00864,
      "operating_gap_inches": 0.02064,
      "verdict": "SAFE"
    }
  },
  "wikidata_grounding": {
    "piston_ring": "Q1127214",
    "internal_combustion_engine": "Q12757"
  }
}