Question

The value of Bending factor of rope used in winding as per CMR-2017 is

• A. 100
• B. 120
• C. 80
• D. 150

Hint:

This is another key number to memorize from the mining regulations.
The D/d ratio is a fundamental concept in wire rope engineering.
A larger ratio means less bending stress and a longer fatigue life for the rope.
100 is the standard minimum for many hoisting applications.

Answer 1

The Correct Option is A

Step 1: Define the bending factor clearly.
The bending factor of a winding rope is the ratio of the drum or sheave diameter $D$ to the rope diameter $d$, written as $\dfrac{D}{d}$.
Step 2: Understand why this ratio matters.
Every time the rope wraps around a drum, its individual wires bend and straighten, if the drum is too small relative to the rope, this bending is severe and repeated flexing quickly fatigues and breaks the wires, so a minimum ratio is enforced by regulation to keep the bending gentle enough for a long safe service life.
Step 3: Recall the regulatory figure.
Regulation 84(2) of the Coal Mines Regulations, 2017 fixes this minimum ratio, requiring the drum or sheave diameter to be not less than 100 times the rope diameter, unless the Chief Inspector approves otherwise in writing.
Step 4: Conclude.
So the standard minimum bending factor $D/d$ for a winding rope under CMR 2017 is 100.
\[ \boxed{100} \]