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Interactive Audio Lesson
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Understanding Cycle Time Components
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Today, we are going to discuss the cycle time of a bulldozer. Can anyone tell me what cycle time consists of?
Is it the time it takes to push earth and come back?
Exactly, Student_1! The cycle time includes cutting, pushing the earth, backtracking, and maneuvering. Let's break it down for clarity. The pushing and backtracking times are variable. Can you see why?
Because it depends on the distance we're pushing the earth?
Correct! The haul distance directly impacts these times. Now, can anyone guess what fixed time refers to in this context?
Is it the time taken for maneuvering operations, like changing gears?
Yes, great job, Student_3! Let's remember: Fixed time is your maneuver time, which includes gear changes and speed adjustments. Keep this in mind when estimating productivity!
Factors Influencing Cycle Time
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Now that we know the cycle time components, what factors do you think can affect push time and backtrack time?
The speed of the bulldozer?
Exactly, Student_4! If the speed increases, the time decreases. And what determines how we calculate this speed?
The performance chart!
Yes, precisely! The performance chart lets us see how speed varies with resistance. Remember, resistance includes rolling resistance from terrain and grade resistance from sloping.
So, if the terrain is hilly, the speed will decrease?
Correct! Increased resistance leads to reduced speed, affecting cycle time. Let's take a moment to summarize: both haul distance and speed are crucial for calculating total cycle time.
Estimating Productivity
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In our discussion on productivity, we need to calculate it in terms of loose cubic meters per hour. Can anyone tell me how we arrive at this number?
By dividing the blade load by the cycle time?
Exactly right! The blade load is critical. Where do we even obtain the blade load from?
From the manufacturer or past field measurements!
That's correct! Excellent work. Keep in mind, after calculating the productivity we must consider job efficiency—how much time the bulldozer is actually operational versus downtime. Can anyone explain how that affects our calculations?
If the machine operates only 40 minutes in an hour, we need to multiply the productivity by that time's fraction?
Correct, Student_2! Always remember to adjust for job efficiency when making your productivity estimates. This is a key aspect!
Introduction & Overview
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Quick Overview
Standard
The section elaborates on defining cycle time in bulldozer operations, including pushing, backtracking, and maneuvering. It highlights how these components impact operational efficiency, emphasizing the importance of haul distance and machine speed in calculating cycle time and productivity.
Detailed
Cycle Time of the Bulldozer
This section provides a comprehensive analysis of the cycle time of bulldozers, distinguishing between the different components of the cycle time, including fixed and variable times. The key elements that make up the cycle time include:
- Cutting and Pushing: This is the time the bulldozer takes to cut the earth and push it to the required location.
- Backtracking: This involves returning to the original position to prepare for the next loading operation.
- Maneuvering: Refers to adjusting speed, changing gears, or any other adjustments necessary for effective operation.
The cycle time is divided into fixed time (related to maneuvering) and variable time (push and backtrack), where the variable time is particularly dependent on haul distance. The longer the haul distance, the more time it will take for pushing and returning.
The section also outlines how to determine the push time, backtrack time, and maneuver time using performance charts. These charts provide data on how speed varies with total resistance and project conditions, allowing for accurate estimates of productivity.
Furthermore, an estimation of productivity using loose cubic meters per hour is presented, explaining how to calculate it based on the blade load and cycle time. Factors affecting job efficiency, such as terrain conditions and operator skill, are also discussed, emphasizing their importance in estimating overall productivity and costs associated with earthmoving operations.
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Audio Book
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Understanding Cycle Time
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So, the time required to push, backtrack and maneuver into position, so that is called as a cycle time of the bulldozer. So, you are going to cut the earth, push the earth, dump it at the required place, then backtrack, backtrack in the sense you are going to return, return back to the original position where you want to do the dosing operation again.
Detailed Explanation
Cycle time refers to the total duration of a complete work process performed by the bulldozer, which includes cutting, pushing, dumping the material, and returning to the start position to repeat the operation. Each of these actions contributes to the overall time, reflecting the bulldozer's efficiency and effectiveness. Cutting involves using the blade to slice into the earth, pushing is the movement of the earth to a dumping site, and backtracking is the bulldozer returning to the starting point for another round of work.
Examples & Analogies
Think of a bulldozer like a chef preparing a meal. The chef first gathers the ingredients (cutting), cooks them (pushing), serves them on a plate (dumping), and then cleans the kitchen before starting again (backtracking). Just like the chef has a routine that includes all steps, the bulldozer follows a routine to efficiently complete its task.
Fixed and Variable Times in Cycle Time
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So, we call this as fixed time, this is fixed time and this one is variable time, your push and backtrack it is called this variable time, why do we call this push time and backtrack time as variable time? Because it is variable depending upon your haul distance. So, greater your haul distance greater will be a push time and return time or backtrack time.
Detailed Explanation
Cycle time consists of fixed and variable components. Fixed time includes the constant duration required for actions like maneuvering (speed adjustments, gear changes). Conversely, variable time changes based on the distance the bulldozer must move materials (haul distance); longer distances require more time to push or return than shorter ones, making the push and backtrack times variable.
Examples & Analogies
Imagine you are running to deliver messages in a neighborhood. If your house is close to your friend's, it takes you less time (variable time) to deliver the message than if your friend lived across town. However, no matter how close or far, adjusting your shoes or running speed (fixed time) takes the same amount of time. Similarly, the bulldozer's cycle time is affected by these fixed and variable factors.
Factors Affecting Push and Backtrack Time
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To know the push time and the backtrack time, I need to know the travel distance or the dozing distance or the haul distance. I need to know the travel distance and I also need to know the speed.
Detailed Explanation
Understanding the push and backtrack times requires knowledge of both the distance to move (dozing distance) and the bulldozer's speed. The distance traveled directly influences how long the bulldozer takes to push material and return. Additionally, the bulldozer’s speed must be determined based on specific project conditions, including both rolling and grade resistance, which can affect performance.
Examples & Analogies
Consider riding a bike. If you know how far you need to go (distance) and how fast you can ride (speed), you can estimate how long your trip will take. For bulldozers, just like in bike riding, knowing distance and speed helps determine the time required for each cycle.
Maneuver Time and Its Influences
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So, already I told you maneuver time is nothing, but the time needed for changing your speed accelerating, changing the gears, or reducing the speed, so that is what is called as a maneuver time. So, this maneuver time will depend upon the type of transmission.
Detailed Explanation
Maneuver time is the time required for important adjustments made during the operation, like changing gears or speeding up. The type of transmission (manual or automatic) affects this time. In a manual transmission, the operator must do it manually, which takes longer than with an automatic transmission that adjusts itself, thereby making the bulldozer more efficient in its cycle time.
Examples & Analogies
Think about driving a car. In a manual car, you must press the clutch and change gears, taking extra time. In contrast, in an automatic car, the gears shift on their own, allowing for a smoother and quicker driving experience. Similarly, bulldozers with automatic transmission save maneuver time compared to those with manual transmission.
Application of the Performance Chart
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So, in the earlier lecture, I discussed about how to determine the speed from the performance chart. So, with the help of the performance chart, you can determine the speed. So, in the performance chart, you will be having the speed in the x-axis and you have the total resistance either in percentage or in rimpull in kg it is given.
Detailed Explanation
Performance charts are valuable tools that illustrate how a bulldozer's speed relates to the resistance it faces. By consulting these charts, operators can find the optimal speed for different working conditions, considering factors like terrain and load. This knowledge allows them to make informed decisions to enhance efficiency and safety during operation.
Examples & Analogies
Imagine looking at a map of a hiking trail. The map shows you how steep the trail is—steeper sections will slow you down. By using the map effectively, you can decide how fast to walk to conserve energy. Similarly, bulldozer operators use performance charts to determine the best speeds for efficient work, based on the terrain they are operating on.
Understanding Productivity Estimation
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Now let us see how to estimate the productivity of the bulldozer. So, we are going to estimate the productivity a lose meter cube per hour. As I told you whenever you express the volume, you should be very specific that whether you are expressing the volume in the loosen state or bank state, that is natural state or in the compacted state.
Detailed Explanation
Estimating productivity involves calculating how much earth the bulldozer can move in a given time frame, typically expressed in cubic meters per hour. It is crucial to clarify whether this measurement refers to the loosened state (after excavation) or bank state (before disturbance). Such specificity ensures accurate assessments of performance capacity during actual operations.
Examples & Analogies
Think of how you measure flour when baking. If a recipe calls for a cup of packed flour versus a cup of sifted flour, each volume is different. In the same way, when measuring productivity, it's essential to specify the state of the material being moved (loosened or bank state) to assess the bulldozer's capability accurately.
Calculating Unit Cost of Production
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So, for that you need to know unit cost is nothing but cost per loose meter cube. Say I am going to find it in the loosen state cost per meter cube of earth moved, I need to calculate. It is nothing but your hourly cost associated with the machine divided by the hourly productivity.
Detailed Explanation
The unit cost of production determines the cost of moving one cubic meter of earth using the bulldozer. This is calculated by dividing the total hourly cost of operating the bulldozer by the hourly productivity rate. Understanding this cost is vital for budgeting, bidding on projects, and making informed financial decisions related to earthmoving operations.
Examples & Analogies
Imagine running a lemonade stand. To find out how much each cup of lemonade costs to make, you divide your total costs (lemons, sugar, cups) by the number of cups sold. Similarly, in construction, knowing the unit cost for moving earth helps managers determine expenses accurately and ensure they stay within budget.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: Composed of cutting, pushing, backtracking, and maneuvering times.
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Variable Time: Time for pushing and backtracking which depends on haul distance.
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Fixed Time: Time related to maneuvering, which is more consistent across operations.
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Productivity Calculation: Blade load divided by cycle time.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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Example of estimating a bulldozer's cycle time involving a push distance and speed determined by a performance chart.
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A scenario illustrating how changing terrain affects bulldozer speed and consequently cycle time.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Cut, push, backtrack, then maneuver with ease, cycle time’s made simple, just remember these!
📖 Fascinating Stories
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Imagine a bulldozer named Bob, who cuts earth all day. Bob pushes dirt, then takes a back trip after each play. Bob changes gears when the load gets tough, but he knows it’s the cycle time that matters the most!
🧠 Other Memory Gems
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P B M C - Push, Backtrack, Maneuver, Cycle - helps remember the key components of bulldozer cycle time.
🎯 Super Acronyms
PBMC - Push, Backtrack, Maneuver, Cycle Time.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Cycle Time
Definition:
The total time taken to complete a cycle of operations including cutting, pushing, backtracking, and maneuvering.
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Term: Push Time
Definition:
Variable time taken to push earth to a designated dump location.
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Term: Backtrack Time
Definition:
Variable time taken to return to the starting position for the next operation.
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Term: Maneuver Time
Definition:
Fixed time needed for changing gears and adjusting speeds.
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Term: Haul Distance
Definition:
The distance over which earth is pushed from the cutting point to the dumping location.