Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skills—perfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Understanding Swell Factor
Unlock Audio Lesson
Let's start with the concept of swell factor. Who can tell me what the swell factor is?
Is it the difference in volume between bank and loose soil?
Exactly! The swell factor is the ratio of loose dry unit weight of the material to the bank dry unit weight. It helps us understand how much the material expands when it's disturbed. Did you know that for push-loaded scrapers, this swell factor increases by 10% due to additional compaction?
Why does the compaction change the swell factor?
Great question! The pressure from the pusher compresses more material into the scraper bowl, increasing its density, thus affecting the swell factor.
Remember, an easy way to recall this is: "More push means more compact, 10% is a handy fact!"
Got it! So we need to use the adjusted swell factor whenever we're calculating loads.
Absolutely, let's summarize: the swell factor critical for understanding the volume of loaded materials and it can vary based on the operational method.
Calculating Total Resistance
Unlock Audio Lesson
Now, let's dive into calculating the total resistance that a scraper faces during operation. Who remembers how we assess this resistance?
We need to look at both the rolling resistance and the grade resistance!
Exactly! Rolling resistance remains constant at 50 kg per ton. Now, if we consider the grades of 5%, 3%, and -3%, how would we convert these grades into kg per ton?
We multiply the grade percentage by 10 to convert to kg per ton!
Correct! So, for example, a 5% grade equals 50 kg per ton. This conversion helps us assess different resistance segments along the haul route.
Let’s remember: "Grade up, resistance up; grade down, resistance down!" This can help when determining overall loads.
So we need to calculate it segment-wise for accuracy?
Yes, breaking it into segments gives us a clear view of the travel resistance at each step!
Balancing Scrapers and Pushers
Unlock Audio Lesson
Moving on, how do we balance the work between scrapers and pushers? Anyone remember how their cycle times play into this?
The pusher cycle time is usually smaller, right? So more scrapers can be served by one pusher.
Exactly! The ratio of cycle times helps determine how many scrapers a pusher can effectively manage. What’s the formula we use?
It’s the scraper cycle time divided by the pusher cycle time!
Correct! And what’s a typical balanced number of scrapers we've discussed?
It can be 5.68 scrapers per pusher based on our calculations!
Right! Since we can’t have a fraction, we have to round it up or down based on operational economics. Always think about balancing efficiency!
So, we could round to either 5 or 6 and then assess our productivity?
Exactly! Remember, efficiency in operations comes from optimal balancing!
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
In this section, we explore the methodologies for calculating the travel time of scrapers in earthmoving operations, including how to balance the workload between scrapers and pushers to enhance efficiency. Key factors such as swell factor, resistance types, and cycle times are discussed in detail.
Detailed
Travel Time Calculation
This section delves into the important topic of travel time calculation for scrapers used in earthmoving operations. It begins by defining the concepts of productivity and the significance of estimating cycle times for related machines, including pushers.
The section outlines the specifics of working with scrapers, emphasizing the influence of factors such as the swell factor (increased by 10% for push-loaded scrapers due to compaction) and rolling resistance (noted as 50 kg per ton). The cycle time is derived from the combination of loading, dumping, and turning times, culminating in the overall efficiency of the operation.
To accurately assess the travel speed, the resistance along different sections of the haul route is computed, reflecting the varying gradients and their conversion into kg per ton. Additionally, the process of segmenting the haul cycle into distinct distances is explained to facilitate precise time calculations.
Finally, the techniques for balancing scrapers and pushers are presented, highlighting how optimal relationships and timing between these interdependent machines can lead to minimized operational costs and maximized productivity.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Overview of Travel Time Components
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The travel time needed for the scraping operation is broken down into several components. This includes the time spent traveling multiple segments of the haul route, loading time, dumping time, turning time, and time spent decelerating.
Detailed Explanation
Travel time calculation involves determining the total time taken for different activities in the scraping operation. This includes the sum of various time intervals spent on travel across segments, loading, and unloading materials. Specifically, each segment is analyzed separately to assess how long the scraper stays in each phase of operation. By adding up these individual times, we obtain the total travel time for the operation.
Examples & Analogies
Think of this like a car journey where you need to account for the time spent driving on different roads, stopping for gas, or taking a break. Just like in that journey, every little stop and travel time needs to be accounted for to plan the total time it takes to get to your destination.
Calculating Segment Travel Times
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
For the first 60 meters, the speed is 7 km/h. This converts to 0.51 minutes. For further segments, speeds vary, necessitating calculations for each section's travel time.
Detailed Explanation
Travel time for each segment is calculated using the formula: Time = Distance / Speed. The speeds are converted from kilometers per hour to meters per minute to facilitate this computation. Each segment is handled separately, ensuring different speeds for varying road conditions are accurately accounted for. For example, if the speed is 7 km/h for the first segment, we convert this speed to meters per minute and divide the distance (60 m) by this speed to find the travel time for that segment.
Examples & Analogies
Imagine timing yourself while cycling through a park. Each path has different speed limits based on how smooth or bumpy it is. Similarly, in scraping operations, different segments may allow for varying speeds, requiring careful calculation of how long each segment will take based on conditions.
Adding Up Total Time
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The total travel time is achieved by summing all the individual segment times as well as loading and dumping times. The loading time is indicated as 0.8 minutes, and the dumping time is 0.37 minutes, contributing to the total cycle time.
Detailed Explanation
After calculating the travel times for each segment of the haul route, we add these times along with fixed times such as loading and unloading. Each of these activities contributes to the overall efficiency and time management of the scraping operation. The formula used here is simply: Total Time = Sum of Travel Times + Loading Time + Dumping Time. This provides a comprehensive understanding of how long the entire scraping cycle will take.
Examples & Analogies
Think about preparing a meal in the kitchen. If making pasta involves boiling water (a fixed time), cooking the pasta (varied time depending on the amount), and serving it (another fixed time), you'd sum all these times to know how long dinner will take. Similarly, in scraping operations, we combine different times for an accurate estimate.
Finalizing Cycle Time
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The final scraper cycle time is calculated, which is the total of the travel time, loading time, and unloading time. This figure is crucial for estimating productivity and determining operational efficiency.
Detailed Explanation
Once we have the total of travel times, loading, and dumping times, we establish the overall scraper cycle time. This crucial metric helps assess how productive the scraping operation is, indicating how many cycles can be completed in an hour and allowing for overall operational efficiency assessments. Understanding cycle times helps in resource allocation and project scheduling.
Examples & Analogies
Think of it like planning a series of appointments. You need to know how long each appointment will take and how long it generally takes to travel between them. By the end of your planning, you have a total time for your day, which tells you how many appointments you can realistically fit in. Similarly, calculating the scraper cycle time tells us how many hauling cycles we can achieve in a specific timeframe.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Swell Factor: Significantly influences the volume and weight of material during transportation.
-
Cycle Time: Involves all phases of the scraper's operation, from loading to hauling and unloading.
-
Resistance Types: Understanding both rolling and grade resistance is essential to estimating accurate travel times.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
A scraper with a maximum heaped capacity of 23.7 cubic meters is loaded to 95% capacity, meaning the operational volume is adjusted accordingly.
-
In calculating travel resistance, a 5% gradient is converted to 50 kg per ton, which affects overall travel speeds.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
-
When we load, we must find, swell factor helps the weight unwind.
📖 Fascinating Stories
-
Picture a scraper load getting heavier; a pusher's push compresses the earth, making it denser and altering the swell factor by 10%.
🧠 Other Memory Gems
-
RGR - Resistance, Grade, and Rolling are the keys to knowing how much weight you’ll be hauling.
🎯 Super Acronyms
RADIUS
- Resistance And Distance In Unit Scrapers for efficient calculations.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Swell Factor
Definition:
The ratio of loose dry unit weight of a material to its bank dry unit weight, indicating volume change upon disturbance.
-
Term: Cycle Time
Definition:
The time taken for a machine to complete one full cycle of operation, including loading, hauling, and dumping.
-
Term: Rolling Resistance
Definition:
The resistance encountered by a machine while moving across a surface, often expressed in kg per ton.
-
Term: Grade Resistance
Definition:
The resistance experienced due to inclination or decline in the surface gradient during hauling.