7.2. Power Requirements of Machines

What is this required power? So, generally, what is the power needed by the machine to overcome the resisting forces in the project site and keep the machine moving, that is what is a required power.

Required power is the amount of power a machine needs to have in order to operate effectively on a construction site. This power is necessary to overcome resistance from the ground and other obstacles so that the equipment can move forward. Each construction site is unique, presenting different conditions that the machinery has to adapt to, thus affecting the total power required.

Think of a bicycle riding on different surfaces: on a smooth pavement, it rolls easily; however, on a sandy beach, it requires more effort to pedal because of the increased resistance from the sand. Similarly, machines need more power to operate in tougher conditions.

What are all the different types of resistances the machine is going to encounter? That is what we are going to see, one is rolling resistance, other one is a grade resistance. We will see what are these rolling resistance and grade resistance one by one in the upcoming slides.

Machines face different forms of resistance when operating, particularly rolling resistance and grade resistance. Rolling resistance is the drag experienced when tires roll over a surface, and grade resistance is the additional force necessary when moving up or down a slope. Understanding these types of resistance is crucial for calculating the total power a machine will require.

Imagine trying to push a toy car on a flat surface (rolling resistance) compared to pushing it up a ramp (grade resistance). Both scenarios require different levels of effort (or power) to perform.

The first thing we will discuss about the 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 occurs due to the interaction between the wheels and the surface they are moving over. It varies depending on the type and condition of the surface, such as concrete, asphalt, or earthen roads. Properly maintained roads reduce this resistance, allowing machines to operate more efficiently.

It's like running on a track versus running on sand. You can run faster and with less effort on a smooth track (less rolling resistance) than on a sandy beach (more rolling resistance).

Basically, we can compare the rolling resistance between hard road and a soft road. So, hard road, you can say a concrete road, your asphalt all these are examples of hard road, your earthen roads are soft road.

The type of surface affects rolling resistance significantly. Hard surfaces like concrete generally provide lower rolling resistance than softer surfaces like earth or gravel. Additionally, the way the road is maintained, such as its compaction and moisture content, plays a critical role in performance.

Consider a shopping cart moving on tiles (hard surface) compared to a carpet (soft surface). The wheels roll more easily on the tiles because there is less friction compared to the thick fibers of the carpet that create more resistance.

Because if you maintain your hauled route, the resistance encountered by your machine will be less. If the resistance is less, your required power to overcome the resistance will be less, if the required power is less your operating expense will be less.

Regular maintenance of haul routes can significantly reduce rolling resistance, leading to lower power requirements for the machine. Less power needed means lower operating costs, which is economically beneficial for the project.

Regularly tuning a car helps it run efficiently and use less fuel. Similarly, keeping construction roads well-maintained helps machines use less power, leading to lower fuel costs.

So, rolling resistance is expressed in kilograms of tractive effort. So, rolling resistance is expressed in kg of your tractive effort needed to move a unit weight of your machine over the particular surface.

Rolling resistance can be quantified in terms of tractive effort required to move a certain weight over a specific type of surface. This quantitative measure is crucial for determining the power needed for effective machine operation.

Just like how we measure the effort (in kilograms) needed to push a cart based on its weight and the surface it’s on, construction machines can have their required effort calculated based on their weight and the type of road surface.

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