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A short class with Sarah and her students. The other ways are under More.
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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.
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.
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.
The total time for one complete operation including loading, hauling, dumping, and returning.
Time components not influenced by travel distance, such as loading and dumping.
Time components influenced by travel distance and speed.
Concept showing that overloading results in decreased loading rates due to material resistance.
Method where a pusher assists a scraper during loading and then retreats.
A technique involving multiple scrapers working in sequence to enhance productivity.
Involves scrapers that continuously move between loading and dumping sites.
Loading, hauling, dumping with grace, Scrapers operate at a steady pace.
Imagine three scrapers working together like a relay race, passing their loads to each other for a faster haul.
Remember 'FIVE LHTDRS' for the components of cycle time: Fixed, Variable, Haul, Turn, Dump, Return, Spot.
FIVE: Fixed, Involved times, Variable, Efficiency - A guide to understanding cycle time.
Term
What is cycle time?
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Term
What comprises fixed time in cycle time?
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Term
What is the load growth curve?
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What is chain loading?
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The total time taken to complete one full operation of loading, hauling, dumping, and returning.
Components of cycle time that do not depend on travel distance, including loading and dumping.
Components of cycle time that depend on travel distance and speed.
A curve illustrating the relationship between loading time and payload percentage, highlighting diminishing returns.
A loading method where the pusher helps the scraper load, then retreats to assist another scraper.
A loading method where multiple scrapers work in sequence to optimize loading and hauling operations.
A loading method involving scrapers that travel between loading and dumping sites for continuous operation.
This section discusses the cycle time components of scrapers and loading methods, highlighting the importance of timing and efficiency in loading operations.
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.
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:
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:
Understanding these components and methods is crucial for optimizing scraper efficiency and productivity in construction and earthmoving operations.