8.2. Factors Affecting Rolling Resistance

Rolling resistance is nothing but what is the resistance offered by the hauled route to the wheel which is rolling over the particular surface.

Rolling resistance refers to the force that opposes the motion of a wheel as it rolls over a surface. This force is influenced by the type of surface the wheel is on. For instance, rolling resistance will be different when moving on concrete compared to loose soil. The main idea here is that whenever equipment moves, it doesn't face just air friction; the surface itself pushes back against the wheels, slowing them down.

Think of riding a bicycle on different surfaces. When you ride on a smooth road (like concrete), it's easier to pedal because there's less resistance. However, if you go onto a sandy beach, pedaling becomes much harder because the sand pushes against your tires, making it more challenging to move forward. This difference in resistance is similar to rolling resistance on various surfaces.

Resistance to the motion of equipment on a level surface is called as rolling resistance. It varies with the type of the hauled route.

The rolling resistance is not uniform; it changes based on the type of surface. For example, a hard surface like asphalt creates less resistance than a soft, uneven surface like an unpaved road. Additionally, well-maintained surfaces tend to have lower resistance compared to those that are poorly maintained. Therefore, understanding the nature of the surface is crucial in estimating how much power will be required for equipment to move efficiently.

Imagine how a car drives on a new, well-maintained highway versus a bumpy dirt road. On the highway, it glides smoothly, using less fuel and energy. But, on the dirt road, the car has to work harder to keep moving, which is similar to how rolling resistance differs between hard and soft surfaces.

Depending upon how you maintain it and prepare the earthen roads, it can even give you a better performance equivalent to hard roads.

The condition of the hauled route significantly impacts rolling resistance. Proper maintenance can create conditions that lower resistance, making it similar to that of hard roads. For instance, regular compaction and ensuring optimal moisture content can keep earthen roads firm and reduce how much the tires sink, thereby reducing resistance during movement.

Consider a garden path. If you keep it clear, firm, and dry, it's easy to walk on, similar to a paved sidewalk. However, if it’s overgrown with grass or muddy, walking will take more effort. The same goes for the machines – well-maintained routes reduce resistance and effort needed to operate.

So, mounting in the sense, it can be either a wheel mounted or it can be a track-mounted.

The type of mounting (wheels vs. tracks) also plays a role in rolling resistance. Wheel-mounted machines generally perform better on hard surfaces, while track-mounted machines (like bulldozers) distribute weight more effectively over weaker surfaces, reducing penetration resistance.

Imagine walking on a frozen lake in high heels versus in snowshoes. The snowshoes are designed to spread out your weight and prevent you from sinking, just as track-mounted equipment spreads out its weight. In contrast, heels put more pressure on a small area, making you sink more - the same principle applies to equipment on different surfaces.

So, rolling resistance is expressed in kilograms of tractive effort or pounds of resistance required to move each ton of the vehicle weight over a level surface of the specified type.

Rolling resistance is typically quantified in terms of 'tractive effort', which can be expressed in kilograms or pounds. This represents how much force is required to move a vehicle across a certain surface. By understanding how much power is necessary to overcome these resistances, operators can choose the appropriate machinery that can manage that level of effort.

When planning a road trip, you consider the fuel your vehicle needs based on how much resistance the road will provide. Just like fuel economy decreases on steep hills or bumpy roads, rolling resistance tells us how much energy our machines will consume as they navigate different surfaces.

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