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Interactive Audio Lesson
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Understanding Cycle Time Components
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Let's start with the basic components of cycle time for scrapers and pushers. Can anyone tell me what factors influence these times?
Is it mainly loading and dumping times?
Exactly! Loading, dumping, and traveling times all contribute to the cycle time. Additionally, the swell factor plays a significant role when calculating weights. What do we remember about the swell factor?
It’s the ratio of loose volume to bank volume! But it increases by 10% when using a pusher, right?
Correct! This increase is due to the additional compaction from the pusher. Remember, it’s essential to account for density changes in material as well.
How do we handle the different loading times?
Great question! We use average times provided by manufacturers, which are crucial for accurate cycle time calculations.
So, knowing these components helps us estimate total cycle time effectively?
Exactly! Let’s summarize: cycle time is affected by loading and dumping times, swell factor, and operational efficiency of the machines. Keep these in mind!
Calculating Productivity
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Now that we understand the factors, let's calculate the productivity of a scraper. If the heaped capacity is 23.70 m³ and we load 95% of that, how much are we loading?
That would be 22.52 m³!
Exactly! Now, when converting to bank volume using the swell factor of 0.80, what’s the volume?
We have to multiply 22.52 by 0.80, which gives us 18.016 m³.
Close! But first, we need to account for the 10% increase in the swell factor due to compaction with the pusher. Can someone calculate that for me?
So we calculate 22.52 * 0.8 * 1.1 = 19.82 m³.
Great job! Knowing how to process these calculations is vital for estimating cycle time realistically.
Balancing Scrapers and Pushers
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We've talked about productivity, now let’s discuss balancing machines. Why do you think it's vital to balance the number of scrapers with the pushers?
To minimize wait time for the machines and maximize productivity! Right?
Exactly! One pusher can assist several scrapers, typically 4 to 5. How can we determine the right number for efficiency?
By comparing their cycle times?
Absolutely! To find the balanced number of scrapers per pusher, we divide the scraper cycle time by the pusher cycle time. Who can recall what those times are?
The scraper cycle time is 7.78 minutes, and the pusher cycle time is 1.37 minutes!
Perfect! Now, can anyone calculate the number of scrapers that can be optimally served by one pusher?
It would be 5.68 scrapers, but we’d round that down, right?
Correct! Thus, we consider the economics for either 5 or 6 scrapers to finalize our decision.
Introduction & Overview
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Quick Overview
Standard
In this section, we delve into the cycle times associated with scrapers and pushers, exploring the influential factors such as swell factor, loading times, and haul distances. We also highlight the importance of balancing the number of scrapers and pushers to optimize productivity within the construction process.
Detailed
Detailed Summary
In this section, we explore the cycle time for scrapers and pushers, key pieces of earth-moving equipment. We begin by discussing the various parameters that affect cycle time, including the swell factor, rolling resistance, and the weight of the material being transported. The swell factor is critical in determining the conversion between loose volume and bank volume of materials, which is essential for accurate weight estimation. Notably, the swell factor increases by 10% when pushers are used, due to additional compaction pressures.
We also detail the operational side, such as the estimated average loading, dumping, and turning times which contribute significantly to the overall cycle time. With the introduction of practical examples, we see how to calculate the production rates and the costs associated with moving earth materials. Another crucial aspect is the coordination of scrapers and pushers; the section illustrates how to balance their use to maximize operational efficiency. Ultimately, understanding cycle time is vital for project planning and execution, ensuring machines operate at optimal capacity and reducing costs.
Audio Book
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Overview of Cycle Time Calculation
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So, now let us work on the first problem on productivity estimation of the scraper. So, a scraper with the assistance of the pusher is moving the dry earth soil having unit weight of 1660 kg per bank meter cube.
Detailed Explanation
In this section, we are focusing on how to estimate the productivity of a scraper and its accompanying equipment, the pusher. A scraper carries dry earth soil, which has a specific unit weight. Understanding the unit weight is crucial for calculating how much material the scraper can effectively transport. The cycle time for both the scraper and the pusher determines the overall efficiency of the earth-moving operation. The goal is to balance the work done by both machines to improve productivity.
Examples & Analogies
Think about it like a team of two workers moving boxes. One worker (the scraper) carries a load of boxes, while the other worker (the pusher) helps load boxes onto the first worker. If the first worker takes too long to load, the second worker has to wait, which means the team isn't working efficiently. By figuring out how long each task takes, we can make sure both workers are busy and moving quickly.
Understanding Swell Factor
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So, hope you remember what is swell factor? We have defined what is swell factor in early lecture, it is a ratio of loose dry unit weight of the material by bank dry unit weight of the material.
Detailed Explanation
The swell factor is a crucial concept in earth moving and excavation. It helps us understand how much volume of material will change when it's moved from one state to another. The ratio is defined as the loose dry unit weight divided by the bank dry unit weight. When pushing soil, the additional pressure from the pusher increases the density of the material (hence increasing the swell factor) due to compaction, which is essential for calculating how much can be moved effectively.
Examples & Analogies
Imagine a sponge filled with water. When you squeeze it (like the pusher), the sponge becomes denser, and more water can be pushed out in a small space. Similarly, when the pusher adds pressure, the soil becomes denser and the amount that can be effectively moved changes.
Calculating the Gross Weight
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So, the gross weight of the machine is nothing but your empty weight plus the weight of the load in the machine.
Detailed Explanation
To accurately calculate how much load can be transported, we need to determine the gross weight of the scraper when it's loaded. This involves adding the empty weight of the scraper to the weight of the load it carries. Understanding the gross weight helps us ensure that we are not exceeding the machine's safe operating limits, which is critical for safety and longevity of the equipment.
Examples & Analogies
This is similar to weighing yourself before and after carrying a heavy backpack. The increase in weight gives you a clear idea of how much you are carrying. In the same way, knowing the empty weight and the load allows us to ensure the vehicle can handle the total weight safely.
Analyzing Resistance in the Haul Route
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Now, we need to find the total resistance.
Detailed Explanation
Total resistance analysis is critical in estimating how much effort the scraper and pusher need to move the load. There are various types of resistance, such as rolling resistance due to the surface and grade resistance depending on the slope of the haul route. Each segment of the haul route has different resistances based on the slope, which needs to be calculated to understand the actual work required by the scraper and pusher.
Examples & Analogies
Picture riding a bike uphill versus downhill. Going uphill (resistance) is harder and requires more effort, while going downhill makes it easier. Just like the resistance helps determine how fast and efficiently you can pedal, it helps us understand how efficiently the scraper can move materials.
Calculating Travel Time
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Now, you can calculate the travel time. So, time is nothing but your distance by speed.
Detailed Explanation
Travel time is essential in understanding how long it takes for the scraper and pusher to complete their cycle. By dividing the distance by the speed, we can estimate how long each segment of the haul route will take. This information allows us to sum the time for the entire journey, helping us to identify any inefficiencies in the operation.
Examples & Analogies
Think of it like driving a car. The distance to your destination is like the haul route, and your speed is how fast you're driving. If you want to know how long the trip will take, you divide the distance by your speed. This calculation helps you plan your time, just like travel time helps plan and improve efficiency in using the scraper.
Determining Total Cycle Time
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If I go for 5 scrapers what will be the associated productivity and production cost?
Detailed Explanation
Total cycle time combines all elements of operation (travel time, loading time, unloading time) into a single figure that reflects how long it takes to complete one full cycle of work. This is crucial in determining the productivity of the scrapers and pushers in terms of how much material is moved and how costs are affected based on their efficiency.
Examples & Analogies
Imagine preparing a meal where you have various tasks: chopping, cooking, and serving. Each task takes time, and you want to know how long your meal preparation will take in total. Understanding total cycle time in this context helps to break down each task and identify how to make the overall process smoother and more efficient.
Balancing Scrapers and Pushers
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So, now the balanced number is 5.68.
Detailed Explanation
Balancing the number of scrapers and pushers is essential for maximizing productivity. It’s calculated by dividing the scraper cycle time by the pusher cycle time to determine how many scrapers can effectively work with one pusher. This balance is crucial to ensure that neither machine has excessive waiting time, maintaining a steady workflow and maximizing productivity.
Examples & Analogies
This is like organizing a relay race where each runner needs to maximize their speed to ensure the next runner is ready without delay. If runners are perfectly timed, the team can finish faster, just like balancing scrapers and pushers keeps the operation running efficiently.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: The total duration to complete an operation involving loading, hauling, and dumping.
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Swell Factor: A critical ratio that affects volume and weight calculations during excavation.
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Productivity Balancing: Achieving an optimal number of scrapers per pusher to enhance workflow.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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If a scraper has a heaped capacity of 23.7 m³ and is loaded to 95%, the effective load volume becomes 22.52 m³. Then considering the swell factor, the bank volume to manage is calculated using the increased swell factor due to compaction by pushers.
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The operational efficiency was benchmarked by estimating that one pusher can operate concurrently with approximately 5 to 6 scrapers, based on their cycle times.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Swell’s that change from loose to tight, ten percent on pushers makes it right!
📖 Fascinating Stories
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Imagine a construction site where pushers are hard at work. As each scraper fills up, the swell factor quietly rises, hiding within the machine's efficiency, revealing the secrets of earth moving.
🧠 Other Memory Gems
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L-D-T – Loading, Dumping, Traveling – the three core components of cycle time!
🎯 Super Acronyms
CYCLE - Comprehensive Yield through Calculated Loading and Efficiency.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Swell Factor
Definition:
A ratio that describes the increase in volume of soil when it is excavated and moved, representing the relationship between loose and bank volumes.
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Term: Cycle Time
Definition:
The total time taken to complete a full operating cycle by a scraper or pusher, including loading, hauling, and dumping.
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Term: Rolling Resistance
Definition:
The force that resists the motion of a vehicle on a surface, typically measured in kg per ton.