Enrol to start learning
Reading is open to everyone. Enrolling is free, and it is what unlocks the audio lessons, practice tests and progress tracking.
5. Cycle Time Calculation
Learn content
Interactive Audio Lesson
Unlock the classroom podcast
The transcript is free to read. A free account plays the conversation back.
Today, we will begin with the back-track loading method. Can anyone tell me what happens once the scraper is fully loaded?
The pusher detaches and goes back to find the next scraper?
Exactly! This movement back to locate the next scraper is termed 'backtracking'.
But why is it considered the slowest loading method?
Good question! It's mainly due to the additional time consumed by the pusher in returning. So, remember, 'Backtrack is Slow' can be our mnemonic.
What are the situations where it’s still preferred?
People often choose it because it allows for cutting material in the same direction, which is preferred in many scenarios.
To summarize, we've learned that back-track loading is slow due to backtracking but is popular for consistent cutting direction.
Unlock the classroom podcast
The transcript is free to read. A free account plays the conversation back.
Now, let's discuss the chain loading method. Student_4, can you explain how this differs from back-track loading?
In chain loading, the pusher stays in one place while the next scraper comes to it instead of returning?
That’s right! This reduction in return time makes the cycle time shorter. Can anyone think of where this method might be most useful?
Is it typically used on long roads or narrow cuts?
Exactly! It's well-suited for those scenarios. Remember, 'Chain is Quick for Roads' to help you recall its purpose.
In summary, chain loading reduces wait time and cycle time, making it effective for long cuts.
Unlock the classroom podcast
The transcript is free to read. A free account plays the conversation back.
Next, we’ll cover shuttle loading. Can someone summarize what happens in this method?
The pusher can push scrapers in both directions?
Yes! It’s commonly applied when you have fill areas in both directions, allowing scrapers to move efficiently.
So, this one also saves time, right?
Correct! As with chain loading, the total cycle time is less. Visualize this — a shuttle working back and forth can enhance efficiency. Remember, 'Shuttle Goes Both Ways'!
Let's summarize: Shuttle loading allows dual direction movement, which significantly lowers cycle time.
Unlock the classroom podcast
The transcript is free to read. A free account plays the conversation back.
Lastly, let's look at how we calculate cycle time using the formula. Does anyone recall the formula for cycle time as discussed?
Tp = 1.4Lt + 0.25?
Absolutely right! Here, Tp is the cycle time of the pusher, and Lt is the scraper load time. Why do you think this formula is important?
It helps us understand the efficiency and timing of lifting material, right?
Exactly! Effective planning and understanding of these cycles can maximize productivity in projects. Remember, 'Timing is Key!'
In summary, the formula helps predict cycle times which are critical for operation scheduling.
Unlock the classroom podcast
The transcript is free to read. A free account plays the conversation back.
Finally, let’s talk about balancing scrapers and pushers. Why is it vital to have the right balance?
If the balance is off, one might have to wait for the other?
Exactly! Matching the number of pushers to the number of scrapers prevents downtime. Any thoughts on how we measure this balance?
Do we use the cycle times to determine how many scrapers a pusher can serve?
Spot on! We can use the ratio of their cycle times to find out the number needing service. Remember: 'Balance Equals Efficiency.'
To wrap up, balancing machinery ensures minimal waiting and optimal productivity on site.
Overview
Short Summary
The section discusses various loading methods for scrapers and their respective cycle times, focusing on back-track, chain, and shuttle loading methods.
Medium Summary
This section details three different loading methods for scrapers: back-track loading, chain loading, and shuttle loading. It highlights the characteristics and time implications of each method, introducing a formula for calculating cycle time and emphasizing the importance of balancing interdependent machines.
Detailed Summary
Detailed Summary of Cycle Time Calculation
This section explores three primary loading methods used in conjunction with scrapers: the back-track loading method, the chain loading method, and the shuttle loading method.
Back-Track Loading
The back-track loading method involves a pusher moving to push a fully loaded scraper in one direction. After loading, the pusher detaches and returns to position itself behind the next scraper, consuming significant time in its backtracking movement. This method is the slowest because of the additional travel time involved but is still popular due to the preference for cutting in a single direction.
Chain Loading
In contrast, the chain loading method reduces return time by allowing the next scraper to wait near the pusher instead of having the pusher return to find it. This method is particularly useful for long, narrow cuts, like roads, and results in a quicker cycle time compared to back-track loading.
Shuttle Loading
The shuttle loading method applies when there are fill areas in both directions. Here, the pusher can switch directions to serve scrapers in both fill directions, which also reduces cycle time compared to back-track loading.
Calculation and Balancing
The section introduces a formula by Caterpillar to determine the cycle time of the pusher based on the loading time of the scraper (Tp = 1.4Lt + 0.25). It emphasizes the importance of balancing the number of scrapers to pushers, as interdependent machines must be correctly matched to minimize waiting times, thus maximizing productivity and reducing costs.
Audio Book
Unlock the audio lesson
The script is above and free to read. A free account plays it back, in the voice you pick.
Create a free accountSo, once the loading of scraper 1 is completed, the pusher will back-track return back and spot the next a scraper, scraper 2 and start pushing it in the same direction... So, one limitation of this back-track loading method is it needs additional time for returning back backtracking.
Detailed Explanation
The back-track loading method involves a pusher that, after loading the first scraper (scraper 1), detaches and returns to find the next scraper (scraper 2). This process creates a delay as the pusher must travel back to the previous location, making this method the slowest option available for loading scrapers. Although it is slower, it is widely used because it maintains a consistent direction for cutting, which many operators prefer.
Examples & Analogies
Imagine a train that has to stop at every station to pick up a passenger. After serving one station, it must return to pick up the next passenger. This makes the process slower, but it's often done this way to keep the passengers on the same route, just like scrapers moving in the same direction.
Unlock the audio lesson
The script is above and free to read. A free account plays it back, in the voice you pick.
Create a free accountSo, this we commonly follow for long cuts, long narrow cuts... So, here also since the returning time is reduced. So, you can say that the chain loading cycle time will be less.
Detailed Explanation
In chain loading, the pusher does not need to return to the previous location after pushing the first scraper. Instead, once scraper 1 is loaded, scraper 2 can come and position itself near the pusher for the next loading. This means that the time to return is significantly less, making the overall cycle time faster and more efficient, especially for long and narrow cuts like roads.
Examples & Analogies
Think of a car in a drive-thru where different customers place their orders sequentially. Once the first customer is served, the next one can pull up and be served without the car driving back to a different spot. This keeps the flow moving efficiently, similar to chain loading.
Unlock the audio lesson
The script is above and free to read. A free account plays it back, in the voice you pick.
Create a free accountThis is not commonly followed, but you can follow it when you have 2 fill areas... So, here also return time is reduced.
Detailed Explanation
Shuttle loading is used when there are two fill areas located in opposite directions. The pusher can load one scraper and then immediately push another scraper in the opposite fill area. Because fill areas are present on both sides, the return time is reduced, leading to a shorter cycle time. However, this method is less common than the other two.
Examples & Analogies
Imagine a mail carrier who can drop off mail at two different locations along the same street without needing to drive back to the post office every time. This efficiency speeds up the delivery process, just like shuttle loading speeds up the scraper loading.
Unlock the audio lesson
The script is above and free to read. A free account plays it back, in the voice you pick.
Create a free accountSo, there is a thumb rule formula given by the caterpillar to determine the cycle time of the pusher... T = 1.4L + 0.25.
Detailed Explanation
To calculate the cycle time of the pusher, we can use the formula: Tp = 1.4Lt + 0.25. In this formula, Tp represents the cycle time of the pusher and Lt represents the loading time of the scraper. This helps in understanding how long it takes for the pusher to complete its task of loading the scraper.
Examples & Analogies
Consider a recipe that tells you how long to boil pasta based on its quantity. If you know how long it takes to boil a certain amount of pasta, you can estimate the overall cooking time based on that quantity, similar to how this formula allows us to estimate the cycle time for scrapers based on loading time.
Unlock the audio lesson
The script is above and free to read. A free account plays it back, in the voice you pick.
Create a free accountAnother important thing as I mentioned earlier, we need to balance the interdependent machines... N = Ts / Tp.
Detailed Explanation
To maximize productivity, it is vital to balance the number of scrapers with the number of pushers. By determining the ratio of cycle times (scraper's cycle time divided by pusher's cycle time), we can find out how many scrapers one pusher can effectively serve without creating wait times. The goal is to keep all machines operating smoothly without delays.
Examples & Analogies
Think of a basketball game where one player is always waiting for the ball to arrive. If there are too many players on one team and not enough on the other, one team will have delays in receiving the ball. Having the right number of players will keep the game flowing smoothly, just like balancing scrapers and pushers keeps the workflow efficient.
--
Key concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
- Back-Track Loading:
A method characterized by the need for the pusher to return to the scraper.
- Chain Loading:
A method that reduces cycle time by positioning the next scraper close to the pusher.
- Shuttle Loading:
A dual-direction loading approach based on available fill areas.
- Cycle Time Calculation:
Important in determining the efficiency and scheduling of equipment operations.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
In a project involving a long narrow road, chain loading would significantly reduce wait times compared to back-track loading.
In operations where material is to be filled in both directions, shuttle loading would enhance efficiency by reducing cycle times.
Memory aids
Imagine a pusher on a construction site. It pushes the first scraper but has to walk back to find the next one, slowly trudging back and forth. Then, think of a pusher in chain loading; it stands still while the next scraper rushes to it!
Flash Cards
Glossary
Back-Track Loading
A loading method where a pusher returns to locate the next scraper after detaching from a fully loaded scraper.
Chain Loading
A loading method where the next scraper waits near the pusher, minimizing return time.
Shuttle Loading
A loading method that allows interaction with scrapers moving in both directions based on multiple fill areas.
Cycle Time
The total time taken for the pusher to perform its duties, determined by loading, positioning, and travel times.
Pusher
A machine that assists scrapers by pushing them during the loading process.
Scraper
A type of heavy equipment used for loading, hauling, and dumping materials.