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Today, we will start by discussing what required power is in the context of earthmoving operations. Required power is essentially the amount of power needed by a machine to overcome the various resistive forces at a project site.
What kind of resistive forces are we talking about, specifically?
Great question! The primary resistive forces include rolling resistance and grade resistance. Rolling resistance occurs when the wheels or tracks of the equipment move over a surface. Can anyone tell me an example of how surface type impacts this?
I think a concrete surface would have less rolling resistance compared to a muddy or soft earth surface.
Exactly! Remember, for hard surfaces like concrete, the rolling resistance is lower than for softer surfaces. The key takeaway is that higher resistance means you need more required power.
Now that we've discussed required power, let’s delve deeper into rolling resistance. Rolling resistance can be broken down into surface resistance and penetration resistance. Who can explain what surface resistance is?
Surface resistance is the resistance a wheel encounters when it rolls over a surface, like asphalt or dirt.
Correct! The type of surface and its condition will heavily influence this resistance. Can anyone give me an example of how maintaining a surface can reduce this resistance?
If an earthen road is well compacted and dry, it would be easier for a vehicle to roll over it compared to a poorly maintained, muddy road.
Exactly. Maintaining the surface can significantly lower the rolling resistance and required power, leading to more economical operations.
Let’s put what we’ve learned into practice. If we have equipment with a gross weight of 20 tons and the rolling resistance is 70 kg per ton, how can we calculate the total tractive effort needed?
We can multiply the gross weight by the rolling resistance value, right?
Correct! In this case, it’s 20 tons times 70 kg per ton, which equals 1400 kg of tractive effort required.
What if the tires sink into the ground? Would that affect our calculation?
Absolutely! That's where penetration resistance comes into play. Each centimeter of penetration adds to the rolling resistance. This is why understanding all components is so crucial.
Now let's connect our understanding of tractive effort to equipment selection. Why is it important to consider rolling and grade resistance when choosing equipment?
Because the equipment needs to have enough power to overcome those resistances to work efficiently.
Exactly! Additionally, selecting the right type based on project requirements like haul distance and material type is crucial. Any thoughts on what specific factors to consider?
The type of material being moved affects what equipment I'll choose, right? Like using a bulldozer versus a backhoe based on whether it's earth or rock.
Exactly right! Knowing the properties of your project site helps in selecting the most effective equipment.
The force needed to overcome resistance and move equipment.
The power necessary to keep the equipment operational against resistive forces.
The resistance caused by the surface over which machinery operates.
Resistance faced when machinery operates on slopes.
Distinction between resistance faced on surfaces and that when tires sink into surfaces.
If a bulldozer with a gross weight of 30 tons has a rolling resistance of 50 kg per ton, the total tractive effort required would be 30 tons x 50 kg/ton = 1500 kg.
In a case where a truck grossing at 25 tons moves over a gravel road with a rolling resistance of 80 kg per ton, the effort necessary would be calculated similarly.
Power to move, resistance must groove, rolling and grade, let’s keep things smooth.
Imagine a bulldozer sinking into mud during a rainy day. The deeper it sinks, the harder it fights to keep moving. Remembering this scene helps us recall how penetration resistance adds to rolling resistance.
RPG for remembering resistances: R for Rolling resistance and P for Penetration resistance and G for Grade resistance.
TRP: Tractive, Required Power, Resistance - essential elements in understanding earthmoving operations.
Term
What is required power?
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Term
What is rolling resistance?
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The usable force required to move a vehicle or equipment at the point of contact with the ground.
The amount of power needed by a machine to overcome resisting forces in order to keep moving.
The resistance encountered by wheels or tracks as they move over a surface.
The additional effort required for a machine to move uphill or downhill on a slope.
Resistance encountered at the surface when equipment rolls over it.
Resistance faced when a tire sinks into the surface, increasing the effort needed to continue moving.
This section delves into the fundamentals of calculating tractive effort in earthmoving operations, including key terms and factors influencing equipment performance.
In this section, we explore the concept of tractive effort in earthmoving operations and how it is calculated. The discussion covers required power, rolling resistance, and grade resistance, alongside the factors like surface and penetration resistance that influence machine performance. Understanding these components is vital for effective equipment selection and project execution.
In earthmoving operations, calculating tractive effort is crucial for determining how much power equipment requires to function effectively. The primary focus of this section is on the concept of required power, which is the power needed to overcome resisting forces at a construction site. These forces can include rolling resistance and grade resistance.
Required Power: The power necessary for the machine to operate against various resistive forces on the project site, ensuring that it can maintain movement.
Rolling Resistance: This is defined as the resistance experienced by the equipment's wheels or tracks as they move over different surfaces. Factors such as the type of surface, wheel size, and inflation pressure significantly affect the amount of rolling resistance encountered. Rolling resistance can be expressed in kilograms of tractive effort needed to move a ton of the vehicle weight over level surfaces.
Grade Resistance: Refers specifically to the additional effort required to move equipment uphill or downhill on a slope, which is considered separately from rolling resistance.
Surface Resistance and Penetration Resistance: Rolling resistance can be divided into these two components. Surface resistance refers to the force against the motion of the equipment that’s moving over a surface, while penetration resistance is related to how deeply a tire sinks into a surface, requiring additional force to keep moving.
Overall, a proper understanding of these parameters enables the effective selection and operation of earthmoving equipment within projects, ensuring that it meets the necessary performance while maximizing efficiency.