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Overview 72

The chapter discusses the various forms of resistance encountered by machines on project sites, including rolling and grade resistance, and how to calculate the total resistance to determine the necessary tractive effort and power requirements of machinery. It emphasizes the importance of using correct power ratings provided by manufacturers and understanding project conditions such as slope and traction to estimate usable power effectively for operational efficiency.

Sections

Rolling Resistance Calculation

This section explains how to calculate rolling resistance and grade resistance for moving vehicles, emphasizing their significance in determining the required power for machines on varying slopes.

1 Section Overview

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1.1 Conversion of Vehicle Weight

This section discusses the conversion of vehicle weight into tons, the calculation of rolling resistance, and the factors affecting tractive efforts needed for project site operations.

1.2 Calculation of Total Rolling Resistance

This section covers the calculation of total rolling resistance, factoring in vehicle weight and penetration resistance.

1.3 Penetration Resistance Calculation

This section covers the calculation of penetration resistance in vehicles, including rolling resistance and grade resistance.

1.4 Total Resistance Calculation

This section covers the calculations involved in determining total resistance for vehicles on haul routes, including rolling resistance and grade resistance.

Grade Resistance Discussion

This section discusses grade resistance and its importance in determining the tractive effort required for machinery operating on slopes.

2 Section Overview

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2.1 Grade Resistance and Assistance

This section explains how to calculate rolling resistance and grade resistance in vehicles, along with the concept of grade assistance when moving downhill.

2.2 Calculating Grade Resistance

This section explains how to calculate rolling and grade resistance for vehicles, helping to determine power requirements for effective machine operation.

Power Requirement Estimation

This section discusses the estimation of power requirements for vehicles, focusing on rolling resistance, penetration resistance, and grade resistance.

3 Section Overview

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3.1 Determining Available Power

This section explains how to calculate the available power needed for heavy machinery to overcome various resistance forces during operation.

3.2 Usable Power Calculation

This section outlines how to calculate usable power for machinery by analyzing resistances such as rolling and grade resistance.

3.3 Rimpull and Drawbar Pull

This section discusses the concepts of rimpull and drawbar pull, highlighting how they relate to vehicle resistance and the requirements for selecting machinery based on resistance calculations.

3.4 Calculating Usable Force

This section discusses calculating the usable force of machinery based on rolling and grade resistance, highlighting the importance of understanding these factors for selecting appropriate equipment.

3.5 Estimating Power Requirements with a Problem Example

This section discusses how to calculate the power requirements of machinery based on rolling resistance and grade resistance.

Learning Objectives

  • Rolling resistance depends on the weight of the machine and is used to calculate total resistance.

  • Grade resistance varies with the slope percentage, affecting the tractive effort required for machinery.

  • Usable power is derived from the total power available from the machine after accounting for various resistances.

Key Concepts

Rolling Resistance

The resistance that opposes the motion of a machine due to its weight, expressed in kg per ton.

Grade Resistance

The additional resistance faced by machinery moving up or down slopes, with its value depending on the slope percentage.

Usable Power

The effective power available for performing work after accounting for resistance forces in a project site.

Tractive Effort

The force required to move equipment against resistance, which varies based on machine weight and type of slope.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting
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