The size of the cut for a cable tray elbow can be calculated using simple geometric formulas based on the tray width and the desired angle or offset.

1. Cut for a Pre-Determined Angle

To create an angled elbow in a cable tray:

1. Determine the angle (B) you want to achieve, e.g., 22°.
2. Calculate the divisor (C): Divide 90° by the desired angle: C = 90° ÷ B → 90 ÷ 22 ≈ 4.09
3. Calculate the cut size (D): Divide the tray width (A) by C: D = A ÷ C → For a 600 mm tray: 600 ÷ 4.09 ≈ 146.7 mm This cut (D) is the triangular section to remove from the side of the tray to form the desired angle .

2. Cut for a Parallel Offset

When routing a tray around an obstacle or creating a parallel offset:

1. Determine the offset distance (e.g., 350 mm) and the straight-line distance over which the offset occurs (e.g., 1500 mm).
2. Divide the straight-line distance by the tray width: 1500 ÷ 600 = 2.5
3. Divide the offset by this factor to get the cut size: 350 ÷ 2.5 = 140 mm This ensures a smooth bend without sharp angles and maintains proper tray alignment .

3. Practical Considerations

• Always measure and mark the first cut before repeating for parallel offsets to ensure accuracy.
• The formulas assume a rectangular tray width; adjustments may be needed for ladder or ventilated trays.
• For multiple cables, ensure the tray fill ratio is within safe limits (typically 40–50% for power or control cables) to maintain airflow and prevent overheating . By applying these formulas, electricians and engineers can accurately cut cable trays for elbows and offsets, ensuring both mechanical stability and proper cable routing.