What is a twin mitered elbow wye?

It is a Y-shaped fitting made by mirroring a segmented (mitered, lobster back) elbow across the vertical centre plane and welding the two elbows together along that plane, over a short common cylindrical stub. With equal diameters everywhere, the centre weld and all miter joints are exact analytic curves, so every flat pattern develops as cosine curves with a computable centre-plane notch.

Which pieces get cut by the centre plane?

The common stub is cut on top by the two first miter planes (a roof-shaped double cosine). Above it, the lower elbow pieces are notched by the centre plane on their extrados side; depending on the bend radius and the number of sectors, one or several pieces are notched, and the lowest ones may even lose material across their full local height near the back generator. The calculator computes the exact notch curve for every piece.

Is this calculator really free?

Yes — 100% free, no registration, no watermark, no time limit. All calculations run in your browser. You can print 1:1 templates and export DXF files (AutoCAD TrueView 2022 compatible) without paying anything.

← Retour

👖 Culotte Deux Coudes (Miroir) — Free online twin mitered elbow wye: a segmented elbow and its mirror image welded together on the vertical centre plane over a common cylindrical stub, exactly like stainless twin-elbow breeches fittings. Computes the roof cut of the stub, the centre-plane notch of every elbow piece, all miter flat patterns, exports DXF, prints 1:1. Built by a pipefitter with 25 years of field experience.

🌐 Language

📏 Units

Diamètre Extérieur (mm)

Angle de chaque coude (°)

Secteurs par coude (pair)

Rayon Cintrage Rm (mm)

Hauteur droite du tronc Lt (mm)

Droit de sortie Lout (mm)

Nombre Génératrices

Pièce à développer

📊 RÉSULTATS

Demi-angle de coupe α

Centre de sortie (X / Z)

Circonférence

N°	X (mm)	Y① (mm)	Y② (mm)

🎮 Vue 3D (glisser pour tourner)

📐 Développé

📖 Formules (Coudes en Miroir)

1. Géométrie de base ▼

α = A / N ; chaque coupe dévie de 2α

h₁ = Lt + Rm·tan(α) ; Lseg = 2·Rm·tan(α)

2. Tronc commun — coupe en toit ▼

Y = Lt + tan(α)·(Rm − r·|cosψ|)

Les deux premiers plans de miter (±α) coupent le tronc en toit. Sommets à ψ = ±90° (points triples), creux à ψ = 0° et 180°.

3. Coupes miter des pièces ▼

bas : t = r·cosθ·tan(α) — haut : t = Lseg − r·cosθ·tan(α)

θ = 0 = intrados (côté extérieur du Y). Embout de sortie : haut = Rm·tan(α) + Lout.

4. Entaille du plan médian ▼

t = −(x_K + r·cosθ·cosφ) / sin(φ)

bord bas réel = max(miter, entaille)

La soudure médiane (x = 0) mange l'extrados des pièces basses. Pièce 1 : transition exactement à θ = ±90°, point triple (0, ±r, h₁). Là où l'entaille dépasse la coupe haute, la pièce n'a pas de matière (chute).

5. Pièces entaillées ▼

Le nombre de pièces touchées par la soudure médiane dépend de Rm, A et N.

6. Encombrement & garde-fous ▼

α doit rester sous 45° (sinon augmenter N). Rm doit dépasser r.