**Example Number 1**

Given a * 40 millimeter diameter* of

*estimate its breaking stress and safe working load.*

**Polypropylene Ropes**We’re using 3D2 because the rope given above is a Polypropylene type of rope.

BS = 3D2 / 300

BS = 3x40x40 / 300

BS = 4,800 / 300

BS = **16**

Therefore, the **Breaking Stress of that Polypropylene type of rope is about 16 tons**

**Now, for the SWL or Safe Working Load, here is how to solve:**

SWL = BS / 6

SWL = 16 tons / 6

SWL = **2.7**

Therefore, the** Safe Working Load of that Polypropylene type of rope is estimated 2.7 tons. **

**----------------------------------------**

**Example Number 2**

Find

*suitable for a load of*

**Manila Rope**

**2 tons.**
We’re using 2D2 because the rope given above is a Manila type of rope, **and here is the formula and how to solve:**

2D2 / 300 x 1/6 = 2 tons of load

D2 = 300 x 6 x 2 tons of load / 2

D2 = 3,600 / 2

D2 = 1,800

D = **42.43 mm** (square root of 1,800)

Therefore, for** a load of 2 tons, 42.43 mm is the smallest suitable for Manila type of rope. **

**----------------------------------------**

**WIRE ROPES**

The breaking stress of a flexible steel Wire Rope is given approximate by the following formula:

* First Formula:* 6 x 12 = 15D2 (tons) / 500

or

* Second Formula: *6 x 24 = 20D2 (tons) / 500

or

* Third Formula:* 6 x37 = 21D2 (tons) / 500

**Where:**

**D** = is the diameter of the rope in millimeter, the safe working load maybe taken as one sixth (1/6) of the breaking stress.

**/ **= divided by sign

**500** = divided by 500 as constant in formula for ropes made out of wires.

**Example:**

Find the Breaking Stress (BS) and Safe Working Load (SWL) of a **6x24, 24mm wire ropes.**

**Here is how to solve:**

According to the problem above, that wire rope is a 24 mm in diameter; therefore, we will use the Second

Formula for Wire Ropes.BS = 20D2 / 500

BS = 20 x 24 x 24 / 500

BS = 11,520 / 500

BS = **23.04 tons**

Therefore, the** Breaking Stress of a 6x24, 24 mm wire rope is 23.04 tons. **

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Now let’s solve for the Safe Working Load of that* 23.04 tons* wire rope and

**here is the process of solving:**

SWL = BS / 6

SWL = 23.04 / 6

SWL = **3.84 tons**

Therefore, the **safe working load for 23.04 tons of wire rope is 3.84 tons.**

**Where:**

* BS* = Breaking Stress

* SWL* = Safe Working Load

* 6* = divided by 6 as constant to the wire rope safe working load formula