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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 learn about the cycle time of a scraper. Can anyone tell me what cycle time includes?
Doesn't it include load time and haul time?
Yes, exactly! Cycle time is defined by several components: Load Time (LT), Haul Time (HT), Dump Time (DT), Return Time (RT), Spotting Time (ST), Turning Time (TT), and ADBT, which stands for Acceleration, Deceleration, and Braking Time.
How do we categorize these times?
Great question! We can divide them into fixed and variable times. Fixed times do not depend on travel distance, while variable times depend on both distance and speed.
What are examples of fixed time?
Examples of fixed time include loading and dumping times, as they do not change with distance. Let's summarize: fixed time includes loading, dumping, and turning, while haul and return are variable.
Now that we've covered the components, how can we differentiate between fixed and variable times?
Fixed time is not affected by how far we travel, right?
Exactly! The loading, dumping, and turning times are fixed because they remain constant regardless of the distance. Now, can anyone tell me what makes haul and return times variable?
That's because it depends on the distance traveled and the speed of the machine.
Right! The speed can be affected by different project conditions, which is why we need to consider these factors when assessing cycle time.
Let's now explore the concept of the load growth curve. Why do we need to be cautious about loading scrapers to full capacity?
Because overloading can reduce the loading rate?
Absolutely! As the bowl gets fuller, the material inside starts resisting incoming earth, which leads to what we call the law of diminishing returns. Can anyone think of a practical implication of this?
Regularly checking the optimal loading time to avoid wasting time?
Yes! Aiming for the optimum loading practices enhances efficiency and reduces unnecessary delays.
Now, let's talk about haul and return times. What can we do to optimize these times?
We need to maintain the haul route well to make it easier for the machine to travel.
Exactly! Maintaining the haul route reduces rolling resistance, which, in turn, increases the travel speed and productivity of the machine. Can anyone suggest methods to maintain the haul route?
Using water trucks and graders!
Correct! Those practices will significantly help in reducing cycle time and enhance productivity.
Let's transition to discussing pusher tractors. How do they assist scrapers in cycle time?
They help reduce the loading time of scrapers!
Correct! They can even serve multiple scrapers. But why is it important to balance the number of pushers with scrapers?
To prevent either from waiting on the other, which would increase the cycle time and reduce efficiency.
Exactly! Balance is key to optimizing production. Now, can anyone list what parts make up the cycle time of a pusher?
Loading time, boost time, maneuver time, and positioning time!
Well done, everyone! Let’s wrap up with a quick recap.
In the cycle time race, Load, Haul, Dump in their place; Fixed times firm, variable can sway, Keep them balanced for work and play.
Once upon a time, in a land of earthmovers, a brave scraper learned the importance of not overloading. It found joy in speeding down well-kept haul routes while keeping its partners, the pusher tractors, balanced for maximum productivity!
To remember the components of cycle time, think 'LHD 2 STT AD,' standing for Load, Haul, Dump, Spotting, Turning, Accelerate, Decelerate.
Remember 'LHTDSTTAD' to recall Load, Haul, Turn, Dump, Spot, Turn, Acceleration, Deceleration - the key components of cycle time!
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What is cycle time?
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What is fixed time?
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What is variable time?
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What happens when scrapers are overloaded?
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Why is maintaining haul routes important?
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The total time required for a scraper to complete a loading, hauling, dumping, and returning operation.
The time taken to load material onto the scraper.
The time taken to transport the loaded scraper to the dump site.
The time taken to unload the material from the scraper.
The time taken for the empty scraper to return to the loading site.
The time taken to position the scraper at the loading site.
The time taken for the scraper to turn during operations.
The time taken for the scraper to increase/decrease speed and to come to a stop.
Components of cycle time that do not depend on travel distance.
Components of cycle time that depend on travel distance.
The cycle time of a scraper consists of several components including load time, haul time, dump time, return time, spotting time, turning time, and acceleration, deceleration, and braking times.
Cycle time is crucial for understanding the efficiency of a scraper. It can be divided into fixed time (loading, dumping, turning, acceleration, deceleration) and variable time (haul and return), which reflect the impact of distance and speed on productivity. Insight into optimum loading practices also helps maximize operational efficiency.
The cycle time of a scraper is defined mathematically as the sum of various time components: Load Time (LT), Haul Time (HT), Dump Time (DT), Return Time (RT), Spotting Time (ST), Turning Time (TT), and Acceleration/Deceleration and Braking Time (ADBT). The important takeaway is that cycle time can be categorized into fixed and variable elements. Fixed times are consistent regardless of distance, including loading, dumping, and turning, while variable times, such as haul and return times, depend significantly on the travel distance and speed of the machine, which, in turn, is influenced by project site conditions. The significance of load growth curves reveals that overfilling a scraper leads to diminishing returns on loading rates. By managing cycle time effectively, especially through proper haul route maintenance, operators can enhance productivity and reduce costs. Furthermore, pusher tractors are utilized for loading scrapers effectively, emphasizing the balance needed between pushers and scrapers for optimal operation.