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A short class with Sarah and her students. The other ways are under More.
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Good afternoon, class! Today we're diving into what makes up the cycle time of a scraper and a pusher. Can anyone tell me what the cycle time includes?
I think it includes load time and dump time.
Exactly! Cycle time is made up of several components, including load time (LT), haul time (HT), dump time (DT), return time (RT), spot time (ST), turn time (TT), and ADBT, which stands for Acceleration, Deceleration, and Braking Time. Now, can someone tell me how we categorize these components?
Are they divided into fixed and variable times?
Correct! Fixed times are those that don't depend on the distance traveled, while variable times like haul and return depend on distance and speed. Remember the acronym F.V. for Fixed and Variable! Can anyone explain why it’s crucial to understand the load time?
Is it because loading time affects overall efficiency?
Exactly! Efficient loading maximizes productivity. Great job today!
Now, let’s talk about the load growth curve. Why do we need to consider this curve when loading a scraper?
It's important because overloading might reduce the loading rate?
Excellent point! The load growth curve illustrates that when you try to load the scraper to its maximum capacity, the rate of loading starts diminishing after a certain point. We shouldn’t try to fill the scraper bowl completely to avoid inefficiency. Can anyone guess what's the maximum payload often recommended?
Something like 85%? That’s when the loading speed decreases.
Exactly! So always aim for optimal loading. This confirms the principle of 'diminishing returns.' Well done, everyone!
Let's move to haul and return time. What factors do you think these times depend upon?
The distance traveled and the speed of the machine?
Correct! Additionally, it’s impacted by project site conditions. Why is maintaining haul routes crucial?
To improve travel speed and reduce costs?
Exactly! Appropriate maintenance increases productivity and decreases costs. Remember, a well-managed haul route saves time and money. Excellent insights today!
Let's wrap up with dump and turn times. What affects the dump time?
The size of the scraper and the type of material being dumped!
Exactly! Larger scrapers and tricky materials lead to longer dump times. And what about turning time?
It varies based on whether the scraper is in a cut area or a fill area.
Great point! The congestion in each area impacts the turn time as well. Always remember this to optimize cycle efficiency. Fantastic engagement today, everyone!
Sum of times for loading, hauling, dumping, and other operations.
Components like loading and dumping that don’t vary with distance.
Time taken for hauling and return trips that depend on distance.
An analytical tool demonstrating diminishing returns when overloading.
The path that needs to be maintained for efficient transport of materials.
When loading's done but goes beyond, the speed does slow, it won't respond.
Imagine a farmer trying to fill a basket; overfilling makes the lid pop, thus slowing down the harvest!
Remember ADBT: Always Drive Brakes Tightly when calculating slowing down times!
F.V. = Fixed time and Variable time: Useful for remembering the categories of time in cycle.
Term
What does LT stand for?
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Term
What is the significance of the load growth curve?
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Total time taken to complete a cycle of operations in earth-moving equipment including loading, hauling, dumping, turning, and returning.
Time components of cycle time not dependent on travel distance, such as loading and dumping.
Time components of cycle time that depend on distance traveled and speed during hauling and returning operations.
Graphical representation showing the diminishing returns when trying to achieve maximum payload in scraping operations.
The path or roadway taken for transporting materials away from the excavation site.
The cycle time for pushers consists of various components that include loading, haul, dump, return, spotting, turning, and acceleration related to their interaction with scrapers.
This section examines the components of cycle time associated with scrapers and their pushers, breaking down the cycle time into fixed and variable elements, explaining the significance of each, and emphasizing the importance of optimizing loading times and haul routes.
Cycle time is a crucial factor in determining productivity in earthmoving operations. It is expressed as:
Cycle Time = LT + HT + DT + RT + ST + TT + ADBT
(Where: LT - Load Time, HT - Haul Time, DT - Dump Time, RT - Return Time, ST - Spot Time, TT - Turn Time, ADBT - Acceleration, Deceleration, Braking Time)
Key components of cycle time can be categorized into fixed and variable times. Fixed time includes all times that do not depend on the distance traveled, such as loading, dumping, turning, and ADBT. Conversely, variable time includes haul and return times, which significantly depend on distance and travel speed influenced by project conditions.
It is essential to recognize that the loading concepts include the ideal loading mechanism to optimize the scraper's capacity, including understanding the load growth curve that shows diminishing returns when overloading the scraper.
Additional components involve proper maintenance of haul routes to minimize travel-related delays and improve machine productivity. Techniques like using bulldozers to rip hard surfaces before scraper loading can enhance efficiency. This section further elaborates on the stages of dump time, turning time in different areas, and the cycle time components for pushers, emphasizing the need to balance the number of scrapers with pushers effectively.