Bundle diameter and cross-section for a mixed-gauge, mixed-construction wire harness — aerospace (M22759, Spec 55), shielded/twisted-pair, and 120 Ω CAN bus wire types, with overbraid, heat-shrink (RNF-100/RNF-3000/HTAT), and Nomex sleeve coverings.
Bundle diameter is computed two independent ways: a real 2D circle-packing algorithm (drives the cross-section diagram — a heuristic greedy tangent-placement packing, not a proven-optimal solution) and the published Glenair Wire Bundle Diameter Calculator multiplication-factor table (a statistical industry cross-check, arithmetic-mean diameter × a count-dependent factor). Wire electrical ratings (M22759, Spec 55) are sourced from manufacturer datasheets; wall thicknesses and most covering-family size tables are representative class figures — see each item's notes and refine against the specific product datasheet before cutting stock. A covering's finished OD assumes the tubing/sleeve wraps snugly against the bundle, a first-order estimate. Actual bundle diameter also depends on lay length and tie/lace spacing — treat this as a planning estimate.
Validated: checking the circle-packing algorithm against exact closed-form cases (2 identical wires → exactly 2× diameter; 3 mutually-tangent identical wires → exactly d×(2/√3+1) = 21.547 mm for d=10 mm) surfaced a real bug — the minimal-enclosing-circle search could get stuck short of the true answer whenever two or more wires tied for "farthest from center" (which happens for any bundle of equal-diameter wires), returning up to ~12% too large a bundle diameter. Fixed 2026-07-24 (now moves toward the averaged direction of every tied wire, not just one) and re-verified against both closed-form cases exactly, plus an independent brute-force search confirming the enclosing circle is now correct for whatever arrangement the (disclosed, non-optimal) greedy packing heuristic produces.
Calculation steps
1. Per-wire overall diameter
insulated OD = conductor(AWG) + 2·wall; twisted pair/shielded categories add layers concentrically (twisted OD = 2×insulated OD — the exact bounding-circle diameter for two touching equal circles)
3 wire group(s), 14 wires total
Signal wires: 8× M22759/32 (XL-ETFE, thin wall) @ 22AWG = ⌀1.044 mm each | Twisted-pair signal: 4× Twisted pair, M22759/34 conductors @ 24AWG = ⌀1.821 mm each | Shielded power: 2× Shielded single conductor, general purpose @ 20AWG = ⌀2.112 mm each
2. Bundle diameter — circle packing (drives the diagram)
Greedy tangent-placement packing: largest wires placed first, each subsequent wire placed tangent to the pair of already-placed wires that keeps it closest to the running centroid; bundle boundary = minimum enclosing circle of all placed wires
14 wires packed
Bundle ⌀ = 7.102 mm (heuristic packing, not a proven-optimal solution)
bundleDiameter = avgWireDiameter × factor(N), factor from the published Glenair Wire Bundle Diameter Calculator reference table (interpolated/extrapolated)
avg diameter = 1.418 mm, N = 14, factor = 4.6
Bundle ⌀ (Glenair estimate) = 6.525 mm — 8.8% difference from the packed result
4. Main covering — RNF-100 heat shrink (TE/Raychem)
Smallest standard size whose as-supplied (expanded) ID ≥ bundle OD selected; finished OD ≈ bundle OD + 2×recovered wall (tubing/sleeve wraps snugly against the bundle regardless of exact shrink fraction — a first-order estimate, disclosed)
Selected size: 3/8" (expanded ⌀9.5 mm, wall 0.64 mm)
Finished ⌀ = 8.382 mm
5. Total copper cross-sectional area
Σ (π/4 × conductorDiameter²), × 2 conductors for twisted/CAN categories
Engineering Calculators