Cable Pulling Tension
The tension at the pulling end of a cable run, through bends and straight sections, and the sidewall pressure at the bend that decides whether the insulation survives.
| Bend angle | Tension out (kN) |
|---|---|
| 0° | 5.45 |
| 45° | 6.78 |
| 90° | 8.47 |
| 180° | 13.31 |
| 270° | 21.06 |
T_out = T_in·e^(μθ) · Through a bend.
P = T/r · Per metre of radius.
A clear path from inputs to results.
The tension at the pulling end of a cable run, through bends and straight sections, and the sidewall pressure at the bend that decides whether the insulation survives.
How to use
- Set incoming tension (kn).
- Set friction coefficient.
- Set bend angle (degrees).
- Set cable weight (n/m).
- Read the headline metrics, then check the table for the detail.
The formula
Reference: Capstan equation through bends; sidewall pressure at the radius.
Worked example
At the default inputs
- Incoming tension (kN): 5; Friction coefficient: 0.3; Bend angle (degrees): 90; Cable weight (N/m): 30; Straight run (m): 50; Bend radius (m): 2
- 1
Pulling tension: 8.47 kN · Sidewall pressure: 4.24 kN/m · Amplification: 1.69× · Bend angle: 90°
Pulling tension: 8.47 kN · Sidewall pressure: 4.24 kN/m · Amplification: 1.69×
Interpreting the result
A 90° bend turns 5.0 kN into 8.47 kN at 4.2 kN/m.
Assumptions & limitations
- Constant friction coefficient.
- Single bend analysed.
Frequently asked questions
What limits the pull?
The cable’s maximum tension and the sidewall pressure at the tightest bend.
Why is a double back so much worse?
The capstan effect is exponential in the angle.
Methodology last reviewed 2026-10-22. Results are informational and not financial or engineering advice — see our disclaimer.