4.2. Rolling Resistance Analysis

Assume the rolling resistance of 50 kg per ton for this particular haul route the rolling resistance is 50 kg per ton. So, if you want to convert it into equivalent gradient, you know that for 1% is a gradient equal to 10 kg per ton. So, 50 kg per ton it is going to be 5%.

Rolling resistance refers to the force that opposes the motion of a vehicle as it rolls on a surface. Here, the rolling resistance is expressed as '50 kg per ton', which means for every ton of weight carried by the scraper, there is an opposing force of 50 kg to be overcome. This resistance can be converted into a percentage gradient. The conversion factor states that a 1% gradient requires overcoming 10 kg per ton. Hence, for 50 kg per ton, the equivalent gradient becomes 5%.

Imagine pushing a car on a flat road. It takes more effort to push the car if the road is muddy or uneven; this represents the rolling resistance. If the road were to slope upward, the effort needed to push the car increases further, similar to how the rolling resistance translates to a gradient in our scenario.

Heaped capacity of the scraper is given as 23.70 meter cube. They expect the load will be 95% of the heaped capacity. So, that means as we discussed earlier, we are not going to load the scraper to its fullest capacity. If we load it to the fullest capacity, it will result in a decrease in loading rate after a particular time.

In operational settings, it's not practical to load the scraper to its maximum capacity (23.70 cubic meters) every time it operates. Instead, an optimal loading of 95% is recommended to maintain efficiency. Loading beyond the optimal limits can lead to performance issues, such as slowed loading rates over time due to the 'law of diminishing returns', which implies that beyond a certain load, each additional unit leads to diminishing increases in productivity.

Think of carrying a backpack. If you fill it to the brim, it becomes unwieldy and heavy, and you can’t move as quickly or easily. However, if you only carry a slightly lighter load, you maintain better speed and efficiency. This is similar to the concept of not fully loading the scraper.

The swell factor has given as 0.80. Swell factor will increase by 10 % due to pushing, because of the additional pressure. The swell factor is a ratio of loose dry unit weight of the material by bank dry unit weight of the material.

The swell factor is a crucial value that indicates how much the volume of soil increases when it is disturbed or loosened (from bank state). Here, the swell factor is initially 0.80, meaning that the loose volume is 80% of the bank volume. When using a pusher, the material becomes more compacted due to added pressure, increasing the swell factor by 10%. Understanding this relationship is vital for accurate calculations of load capacities and the expected density of materials in operational contexts.

Consider a sponge. When it’s dry (bank state), it occupies a certain volume. Once you soak it with water (loosened state), it expands and occupies more space. This is similar to how the swell factor explains changes in volume when soil is disturbed.

The maximum rated load it can carry is 34,019.42 kg. We have to check whether your load or material within your bowl is going to be within this safe operating weight.

The safe operating weight is a defined limit by the manufacturer, indicating the maximum load the scraper can handle without risking damage. Exceeding this weight can compromise the equipment's structural integrity and safety. It’s crucial to ensure that the actual weight of material being moved (in this case, 32,901.2 kg) stays below this limit (34,019.42 kg) to avoid potential equipment failure or accidents.

Think of it like a car's weight limit. If you fill your car with passengers and cargo, there’s a maximum weight it can safely carry. Exceeding that limit can affect the vehicle’s performance and can be dangerous. In our case, ensuring the scraper stays under its limit protects both the equipment and the crew.

Now we need to find the total resistance. The rolling resistance is uniform throughout the haul route. Is given in the question is 50 kg per ton or equivalent gradient as 5%.

The total resistance encountered by the scraper while moving across different segments of the haul route includes both rolling and gradient (grade) resistance. The rolling resistance is consistent across the journey at 50 kg per ton or a 5% gradient. By understanding and calculating the resistance for each segment of the haul route, you can ascertain the effort the scraper must exert to move effectively.

When riding a bicycle, the resistance you feel comes from the ground's surface (rolling resistance) and the incline of the road (gradient). Calculating both types gives you a clearer picture of how much energy you will need to exert to maintain speed.

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