7.1 - Summary of Key Points
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.
Back-Track Loading Method
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s begin by discussing the back-track loading method. Can anyone tell me its main characteristic?
I think it involves the pusher going back to load another scraper?
Exactly! The pusher has to return to spot the next scraper after the first one is loaded. That's why we call it 'back-tracking.' It's considered the slowest method because this return process takes time.
But why do people prefer this method?
Good question! Despite being slower, it allows for cutting in the same direction, which many operators find easier. Remember: 'Back-track = slow track.'
So what’s the main downside?
The return time is a significant downside, making it less efficient compared to the other loading methods we'll discuss.
Can you summarize the back-track loading method?
Sure! The back-track loading method is the slowest due to the time needed for the pusher to return after loading a scraper, preferred for its directionality.
Chain Loading Method
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Next, let’s explore the chain loading method. Who can explain how this differs from back-track loading?
I think the pusher doesn’t have to return to get the next scraper, right?
Exactly! Once the first scraper is loaded, the next one can directly come to the pusher. This reduces the overall cycle time considerably.
In what scenarios is chain loading most useful?
Chain loading is particularly suited for long, narrow cuts, like roads. To remember, think of 'Chain = No Backtrack.'
So, it's faster than back-track loading?
Yes, due to the reduced return time, it enhances efficiency.
Can you summarize this method?
Certainly! Chain loading allows for quicker loading cycles as the next scraper can come to the pusher without the need for any backtracking.
Shuttle Loading Method
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s talk about shuttle loading. What do you think it involves?
I guess it’s when scrapers are moving in both directions?
Exactly! Shuttle loading is used when two fill areas exist, allowing scrapers to be pushed in opposite directions. What do you think its main advantage is?
It reduces the time the pusher spends moving back, right?
That's correct! The cycle time decreases, making it more efficient. Remember, 'Shuttle = Fast & Flexible.'
Is this method commonly used?
Not as much as the back-track or chain methods, but it has specific applications, especially where materials need to be moved in either direction.
Can you sum it up for us?
Absolutely! Shuttle loading allows scrapers to be moved in both directions, decreasing cycle time when two fill areas are available.
Balancing Scrapers and Pushers
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Finally, let’s discuss the importance of balancing scrapers and pushers. Why is this important?
To not have one waiting for the other?
Yes! Balancing their numbers minimizes waiting time and maximizes productivity. Can anyone recall the formula for finding the number of scrapers served by one pusher?
Is it the cycle time of the scraper divided by the cycle time of the pusher?
Exactly right! Remember to balance these interdependent machines to maintain efficiency: 'Balanced = Productive.'
Can you summarize why balancing is essential?
Certainly! Balancing scrapers and pushers reduces waiting time and enhances productivity, ensuring machines work at their optimal capacity.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section discusses three main loading methods for scrapers: back-track loading, the slowest method due to its return time; chain loading, suitable for long cuts, which reduces return time; and shuttle loading, which allows simultaneous movement towards two fill areas. It emphasizes the importance of balancing scrapers and pushers for improved productivity.
Detailed
Detailed Summary
In this section, various loading methods utilized for scrapers in construction work are described. The back-track loading method is the slowest because it requires the pusher to return after each load, thereby increasing the cycle time. Despite this limitation, it remains popular since it allows for consistent cutting in the same direction.
The chain loading method is preferred for long, narrow cuts, such as roads, as it allows the next scraper to wait for loading without the need for the pusher to backtrack, thereby reducing cycle time significantly.
The shuttle loading method, though less commonly used, permits scrapers to be pushed in both directions when two fill areas are available, thus also decreasing the cycle time.
An important formula is presented for calculating the cycle time of the pusher based on the loading time of the scraper:
T_p = 1.4L_t + 0.25
Additionally, the interdependence of scrapers and pushers is discussed, noting the necessity for balancing their numbers to minimize waiting times, consequently enhancing productivity. One pusher can typically serve several scrapers, allowing operations to run efficiently.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Back-Track Loading Method
Chapter 1 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Back-track loading method is the slowest of all the methods because of the additional pusher travel time for backtracking on returning. But most commonly followed because people prefer cutting in the same direction.
Detailed Explanation
The back-track loading method involves a pusher that moves to load a scraper, and once the scraper is fully loaded, the pusher detaches itself and travels back to find the next scraper to load. This process is called backtracking and takes additional time, making it the slowest method. Despite this, it remains popular because operators prefer to maintain a consistent cutting direction, which simplifies operations and reduces potential complications.
Examples & Analogies
Imagine a train that has to travel back to the station to pick up the next passenger after it has dropped off passengers. While it takes time to come back, it ensures that all passengers enjoy a smooth ride without direction changes. Similarly, in construction, workers often prefer the back-track method as it keeps the workflow streamlined.
Chain Loading Method
Chapter 2 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Chain loading is suited for long and narrow cuts. Here, the return time is reduced because once a scraper is fully loaded, the next scraper waits nearby rather than requiring the pusher to backtrack.
Detailed Explanation
In the chain loading method, as soon as one scraper becomes fully loaded, it doesn't require the pusher to return all the way back. Instead, the next scraper waits near the pusher, allowing for a faster transition to push the next scraper. This reduction in return time increases efficiency, making this method suitable for long and narrow construction projects, like roads.
Examples & Analogies
Think of a line of students shaking hands with a teacher. Once one student has finished, they can quickly move aside while the next student steps forward, rather than the teacher walking back to the end of the line every time. This efficiency in movement reflects how chain loading improves the flow in operations.
Shuttle Loading Method
Chapter 3 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Shuttle loading requires two separate fill areas in opposite directions. Here, the pusher moves back and forth, allowing for scrapers to operate in both directions, which reduces return time.
Detailed Explanation
In shuttle loading, the pusher can push scrapers in two directions because there are fill areas on both sides. Once a scraper is loaded, the pusher detaches and pushes a different scraper heading in the opposite direction. This method is less common but effective for operations needing material placed in various spots, as it effectively minimizes travel and waiting times.
Examples & Analogies
Imagine a ferry that can transport people and cars from two docks on opposite sides. Rather than taking a long route and coming back, it directly drops off and picks up passengers from both sides, significantly speeding up its service. Similarly, shuttle loading effectively utilizes resources by allowing scrapers to move in both directions.
Cycle Time and Balancing Machines
Chapter 4 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
A thumb rule formula is given to determine the cycle time of the pusher using the loading time of the scraper. Additionally, balancing the number of scrapers and pushers is crucial to reduce waiting times and improve efficiency.
Detailed Explanation
To calculate the cycle time of the pusher (Tp), you can use the loading time of the scraper (Lt) with the formula: Tp = 1.4Lt + 0.25. This helps in scheduling and efficiency optimization. Furthermore, having the right balance between scrapers and pushers is essential; too many scrapers or pushers can lead to longer waiting times and disrupt the workflow.
Examples & Analogies
Consider a restaurant kitchen where too many cooks can lead to chaos, and not enough cooks can slow things down. The ideal number of cooks ensures that orders are processed smoothly and efficiently, maintaining a steady flow in the kitchen. Similarly, balancing the number of scrapers and pushers ensures everything runs smoothly on the construction site.
Key Concepts
-
Back-track Loading: Slow method; requires pusher to return.
-
Chain Loading: Faster method as the next scraper waits without backtracking.
-
Shuttle Loading: Moves scrapers in opposite directions; efficient with two fill areas.
-
Balancing: Essential for minimizing waiting times and maximizing productivity.
Examples & Applications
In a construction site for a road, the chain loading method is preferred because scrapers can continuously load without delays.
In a scenario with two fill areas on opposite sides, shuttle loading would allow for efficient material transport without unnecessary returns.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
When back-tracking takes too long, chain loading speeds things along.
Stories
Imagine a construction site where a pusher has to run back and forth after loading each scraper, making it slow. One day, a wise operator introduced chain loading, and the scrapers waited patiently to reduce the waiting times.
Memory Tools
For 'B' (Back-track) remember 'Slow,' for 'C' (Chain) think 'Fast,' and for 'S' (Shuttle) keep in mind 'Flex.'
Acronyms
BCS
Back-track is Slow
Chain is Fast
Shuttle is Flexible.
Flash Cards
Glossary
- Backtrack Loading
A loading method where the pusher returns to load the next scraper after fully loading the previous one.
- Chain Loading
A loading method where the next scraper comes to the pusher without requiring the pusher to backtrack.
- Shuttle Loading
A loading method used when two fill areas exist, allowing scrapers to be pushed in opposite directions.
- Cycle Time
The total time taken to complete one cycle of operations with the scraper and pusher.
- Interdependence
The relationship between scrapers and pushers where the efficiency of one affects the other.
Reference links
Supplementary resources to enhance your learning experience.