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 Cycle Time
Unlock Audio Lesson
Today, we're going to explore the concept of cycle time. Can anyone tell me what makes up the cycle time for a scraper?
Is it just how long the scraper takes to move materials?
Good start! Cycle time includes multiple components: fixed time and variable time. Can anyone name some components of fixed time?
Like loading and dumping times?
Exactly! Fixed time includes loading, dumping, and turning times. Now, variable time—what influences that?
Travel distance and machine speed?
Correct! Variables depend on how far the scraper hauls materials and its speed. Remember this acronym, 'LHTDRS': Load, Haul, Turn, Dump, Return, Spot. It's a great way to recall these elements!
Summary: Cycle time consists of fixed and variable components, which influence scraper efficiency in operations.
Load Growth Curve
Unlock Audio Lesson
Let's move on to the load growth curve. Why do you think loading a scraper to its maximum capacity might not be beneficial?
Maybe because it can cause too much resistance?
Exactly! As the bowl fills up, it offers resistance to new material, where our loading rate decreases after a certain point. This is termed the 'law of diminishing returns'. What do you think is the optimal loading percentage?
Around 85%?
Right! Loading around 85% is optimal to maintain efficiency. To visualize, remember this mnemonic: 'Less Is More' when loading scrapers.
Summary: Loading beyond optimal levels can diminish efficiency. The load growth curve helps identify the best loading practices.
Loading Methods
Unlock Audio Lesson
Now, let's discuss the loading methods we mentioned earlier. Can anyone name them?
Back-track loading and chain loading!
Correct! Let’s break these down. In back-track loading, the pusher assists the scraper during loading and then retreats. What happens in chain loading?
Multiple scrapers work together in a sequence!
Spot on! Lastly, shuttle loading involves scrapers traveling between the loading and dumping sites. Can you think of situations where one might be preferred over the others?
Back-track loading might be better in tight spaces.
Absolutely! Choosing the right method can depend on the site conditions. Remember: 'Choose Wisely, Load Efficiently' — a motto for effective loading practices.
Summary: We covered three loading methods: back-track, chain, and shuttle loading, emphasizing their effectiveness based on site conditions.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section examines how cycle time is divided into fixed and variable components, explains loading methods such as back-track loading, chain loading, and shuttle loading, and emphasizes the role of project site conditions and equipment compatibility in optimizing loading efficiency.
Detailed
Loading Methods - Section 2.2
The concept of cycle time in scraper operations consists of several components, which can be categorized into fixed and variable time. Fixed time does not depend on the travel distance and includes:
- Loading Time: Consistent across scraper sizes, it is primarily influenced by the assistance of a pusher loader. The average load time for common earth is approximately 0.8 minutes.
- Dumping Time: Varies based on scraper size and material characteristics, such as cohesiveness and constraints at the dumping site.
- Turning and ADBT: The time taken for acceleration, deceleration, and braking.
Variable time is affected by both haul and return distances, which are determined by project conditions and the machine's speed.
The load growth curve illustrates the phenomenon of diminishing returns, indicating that attempting to load a scraper to its maximum capacity can reduce loading rates due to increased resistance from already loaded material.
In addition to cycle time, this section introduces three primary loading methods:
1. Back-Track Loading: The pusher assists the scraper during loading, then retreats.
2. Chain Loading: Uses multiple scrapers in a sequence for continuous operation.
3. Shuttle Loading: Involves scrapers that travel between loading and dumping sites.
Understanding these components and methods is crucial for optimizing scraper efficiency and productivity in construction and earthmoving operations.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding Cycle Time
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Cycle time = LT + HT + DT + RT + ST + TT + ADBT (Where, LT-Load, HT-Haul, DT-Dump, RT-Return, ST-Spot, TT-Turn, ADBT- Acceleration, Deceleration, and Braking)
Detailed Explanation
Cycle time is the total time taken to complete a single operation cycle of a scraper, combining various time components such as loading, hauling, dumping, returning, spotting, turning, and ADBT (acceleration, deceleration, and braking). This formula provides a comprehensive overview of how long it takes for the scraper to process an entire load, from loading to returning to the start point for the next load.
Examples & Analogies
Think of a delivery service. Just as a delivery truck has to pick up a package (loading), drive to a customer (hauling), deliver the package (dumping), return to the depot (returning), and then get ready for the next delivery (spotting and turning), a scraper follows its own cycle with specific time components that add up to the total time taken to complete a loading task.
Fixed vs. Variable Time Components
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
You can split the cycle time into two parts: fixed time and variable time. Fixed time does not depend on the travel distance and includes loading, dumping, turning, accelerating, and decelerating. Variable time includes haul and return times, which are significantly dependent on travel distance and machine speed.
Detailed Explanation
The cycle time can be divided into fixed and variable components. Fixed time is consistent and does not change regardless of travel distance. Examples include the time taken to load, turn, and dump. On the other hand, variable time is affected by how far the scraper needs to travel and the speed at which it moves. The variable time changes based on the project conditions, such as terrain resistance and the machine's capabilities.
Examples & Analogies
Imagine cooking a meal. Preparing ingredients (fixed time) takes the same amount of time, regardless of how far you have to walk to the stove (variable time). If you have to go across the house for spices, the walking time adds to your cooking time, just as haul and return times add to the cycle time of the scraper.
Loading Time of the Scraper
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The loading time of the scraper is fairly consistent, irrespective of the scraper size. Average load time for a pusher loaded scraper in common earth is about 0.8 minutes.
Detailed Explanation
Loading time remains largely unchanged regardless of the size of the scraper because larger scrapers are often assisted by pusher loaders, which boost efficiency. Manufacturers can provide precise loading times according to specific equipment and material types, like the standard 0.8 minutes for common earth.
Examples & Analogies
Consider a car wash. Whether you drive a compact car or a larger SUV, the time it takes to wash the vehicle might not differ much if the washing machine is designed to handle both types. Just as a pusher system keeps loading times consistent, a well-designed car wash serves vehicles efficiently.
Load Growth Curve
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Loading scrapers to the maximum capacity will reduce rather than increase the rate of production. As the bowl fills beyond 85%, resistance from existing material reduces the loading rate, illustrating the law of diminishing returns.
Detailed Explanation
It's important to avoid overloading scrapers, as filling them to capacity can actually hinder loading efficiency. When the bowl is nearly full, incoming material faces more resistance, causing the loading rate to drop. This highlights the necessity of determining an optimum loading capacity to maximize productivity.
Examples & Analogies
Try pouring a cup of sugar. Initially, it fills easily, but as it gets close to the top, it is harder to pour in without spilling. Instead of maximizing output (filling to the brim), it's more effective to maintain a level that allows smooth pouring, just like loading scrapers.
Maintaining Haul Routes
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Haul and return time depends upon distance and travel speed, which are influenced by project site conditions. Maintaining haul routes can significantly enhance productivity and reduce cycle time.
Detailed Explanation
The efficiency of a scraper's cycle is heavily influenced by how well the haul routes are maintained. Proper upkeep reduces rolling resistance and enhances machine speed, leading to faster and more productive operations. This includes using graders or bulldozers for maintenance and controlling dust to improve visibility.
Examples & Analogies
Imagine driving a car on a well-maintained highway versus a bumpy dirt road. You can travel faster and more smoothly on the highway, just as scrapers perform better on properly maintained roads.
Dump Time Factors
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Dump time depends on scraper size, material type, and dump area constraints. Bigger scrapers take longer to dump, and cohesive materials increase dumping time. Dumping procedures vary based on site constraints.
Detailed Explanation
The time it takes to dump a load can vary widely based on several factors, including the size of the scraper and whether the material is loose or sticky. Narrow dumping sites with high congestion can also cause delays. Understanding these variables is crucial for efficient operations.
Examples & Analogies
Think of emptying a backpack full of sand versus a backpack full of toys. The sand (cohesive material) takes longer to pour out because it clumps together, whereas toys (loose material) come out quickly. Similarly, larger scrapers and congested sites can slow down dump times.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Cycle Time: The total time for one complete operation including loading, hauling, dumping, and returning.
-
Fixed Time: Time components not influenced by travel distance, such as loading and dumping.
-
Variable Time: Time components influenced by travel distance and speed.
-
Load Growth Curve: Concept showing that overloading results in decreased loading rates due to material resistance.
-
Back-Track Loading: Method where a pusher assists a scraper during loading and then retreats.
-
Chain Loading: A technique involving multiple scrapers working in sequence to enhance productivity.
-
Shuttle Loading: Involves scrapers that continuously move between loading and dumping sites.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
A scraper with a load time of 0.8 minutes for common earth, demonstrating the consistent loading time irrespective of scraper size.
-
In back-track loading, as the pusher retreats after helping a scraper, it can quickly assist another, optimizing time efficiency.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
-
Loading, hauling, dumping with grace, Scrapers operate at a steady pace.
📖 Fascinating Stories
-
Imagine three scrapers working together like a relay race, passing their loads to each other for a faster haul.
🧠 Other Memory Gems
-
Remember 'FIVE LHTDRS' for the components of cycle time: Fixed, Variable, Haul, Turn, Dump, Return, Spot.
🎯 Super Acronyms
FIVE
- Fixed
- Involved times
- Variable
- Efficiency - A guide to understanding cycle time.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Cycle Time
Definition:
The total time taken to complete one full operation of loading, hauling, dumping, and returning.
-
Term: Fixed Time
Definition:
Components of cycle time that do not depend on travel distance, including loading and dumping.
-
Term: Variable Time
Definition:
Components of cycle time that depend on travel distance and speed.
-
Term: Load Growth Curve
Definition:
A curve illustrating the relationship between loading time and payload percentage, highlighting diminishing returns.
-
Term: BackTrack Loading
Definition:
A loading method where the pusher helps the scraper load, then retreats to assist another scraper.
-
Term: Chain Loading
Definition:
A loading method where multiple scrapers work in sequence to optimize loading and hauling operations.
-
Term: Shuttle Loading
Definition:
A loading method involving scrapers that travel between loading and dumping sites for continuous operation.