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Interactive Audio Lesson
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Understanding Cycle Time
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Today we're discussing cycle time for bulldozers. Can anyone tell me what cycle time refers to?
It's the total time to complete a task, right?
Exactly! Cycle time includes both fixed time and variable time components. The fixed time doesn't change, while variable time does depend on factors like haul distance. Can someone explain how these times affect productivity?
The shorter the cycle time, the more productive the bulldozer can be, right?
Right! Remember, we have fixed times like maneuvering gear changes. A good memory aid is the acronym 'FAV'—Fixed-time Adjustments and Variable-time performance. Always keep that in mind!
How does the type of transmission affect fixed time?
Great question! Direct transmission takes longer than power shift mode due to manual gear changes versus automatic ones. These differences impact overall efficiency and should be considered in estimations.
Is there a specific formula to calculate these times?
Yes! If you know the haul distance and speed, you can calculate push time. It's all interconnected! Remember, good estimates lead to better planning for productivity.
In summary, understanding cycle time helps improve productivity. Remember the terms fixed time and variable time carefully!
Performance Charts
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Now, let's discuss performance charts. They help us know the speed of our bulldozer, which is vital for calculating cycle time.
How do we read those charts?
The speed is on one axis, and the total resistance on the other. Can anyone guess what factors we consider for total resistance?
Rolling resistance and grade resistance?
Exactly! Remember 'RG'—Rolling and Grade resistance. By knowing these, we can accurately determine how fast our bulldozer can operate.
What happens if we underestimate these factors?
We might overestimate productivity, ultimately affecting our project planning and costs. This is why understanding these charts is crucial.
Can you show us an example?
Sure! Let's say the performance chart indicates a speed of 5 meters per second based on our project’s rolling resistance. We can now calculate push time accurately.
In summary, understanding performance charts enhances our ability to estimate bulldozer productivity accurately.
Estimating Productivity
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Now we’ll estimate productivity! Can anyone remind us how we calculate productivity in earthmoving using bulldozers?
Is it the blade load divided by cycle time?
Exactly! What do we need to know for blade load?
The type of blade and its capacity?
Absolutely! Additionally, knowing the haul distance and speed is crucial as they influence cycle times. Don't forget the acronym 'BLHS'—Blade Load, Haul, Speed.
What about job efficiency?
Good point! Always factor in job efficiency; machines usually work less than 60 minutes an hour. What could be a typical efficiency?
It could be around 45 minutes or so, right?
Exactly! That brings us to adjusting our productivity calculations based on efficiency. In summary, for each machine operation, consider load, cycle time, efficiency, and project conditions.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section elaborates on cycle time for bulldozer operations, identifying the fixed time (related to gear changes and maneuvering adjustments) and variable time (dependent on haul distance and speed). Understanding these concepts is crucial for accurate productivity estimations in earthmoving operations.
Detailed
Fixed Time and Variable Time
In bulldozer operations, the total cycle time necessary for tasks, such as cutting and pushing earth, comprises both fixed and variable components.
Key Components of Cycle Time:
- Fixed Time: Refers to the constant time required for actions that do not vary with the task's distance or conditions. This includes:
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Maneuvering: Adjustments made while operating the dozer, such as changing gears or accelerating. The time needed here is influenced by the type of transmission system in the bulldozer.
- Direct Transmission requires manual gear changes and takes longer (0.1 minutes).
- Power Shift Transmission allows automatic gear changes and is quicker (0.05 minutes).
- Variable Time: This part of the cycle time changes based on project conditions and includes:
- Push Time: The duration the bulldozer takes to push material to a desired location. This time is variable and heavily influenced by:
- Haul Distance: The greater the distance, the longer the push time.
- Speed of the Dozer: Determined by project-specific conditions, such as resistance from terrain and grade.
- Return/Backtrack Time: The time taken to return to the original position after dumping material, which is usually shorter than the push time since the blade is empty and the dozer can travel faster.
For effective productivity estimation, knowing these times allows operators to calculate the bulldozer's output in loose meter cubes per hour, factoring in machine efficiencies and operational characteristics. Efficiencies impact the total operational time, typically working less than 60 minutes per hour in real project conditions.
Additionally, different methodologies exist for estimating productivity. These include:
- Using performance charts and equipment handbooks.
- Applying thumb rules based on horsepower.
Audio Book
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Understanding Cycle Time
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So, this cutting and pushing will go together. So, the time required to push, backtrack and maneuver into position, so that is called as a cycle time of the bulldozer.
Detailed Explanation
Cycle time is the total duration taken for a bulldozer to complete one full operation, which includes cutting earth, pushing it to a dumping location, and returning to begin the process again. Each part of this operation is essential for effective earthmoving.
Examples & Analogies
Think of cycle time like a round of golf. Each hole requires you to drive the ball, navigate the course, and return to your starting position before moving to the next hole. Similarly, a bulldozer must complete its task and return, all within a given cycle time.
Maneuvering Time
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So, other things are maneuvering, maneuvering in the sense whatever adjustments you do, like for increasing the speed, accelerating or decreasing the speed, changing the gear...
Detailed Explanation
Maneuvering time refers to the adjustments made to the bulldozer during operation, such as changing speeds or gears. This time is crucial because it can affect the overall efficiency of the machine during operation.
Examples & Analogies
Consider driving a car where speeding up and changing gears are essential to maintaining speed and control. If you take too long to change gears, it can slow you down just as it does for a bulldozer when maneuvering.
Fixed Time vs. Variable 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...
Detailed Explanation
In bulldozer operations, time can be categorized as fixed or variable. Fixed time includes consistent times required for maneuvering, while variable time changes depending on conditions such as haul distance, which is the distance over which the bulldozer must push material. The greater the distance, the longer the variable time.
Examples & Analogies
Imagine a delivery driver: their fixed time includes stopping at traffic lights and making turns, while their variable time might depend on how far they have to drive. The longer the drive, the longer the variable time.
Calculating Push Time and Backtrack Time
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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
To accurately calculate push time and backtrack time, you need to understand the haul distance. Push time increases with the distance the material needs to be moved, while backtrack time, which is the return trip, is similarly affected. Therefore, haul distance is a key factor in estimating productivity.
Examples & Analogies
Think about pushing a cart. The farther you need to push it, the more time it will take. Similarly, the bulldozer's efficiency can be impacted by how far it needs to travel to dump its load.
Factors Influencing Speed
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So, to know the push time and the backtrack time, I need to know the travel distance or the dozing distance or the haul distance... So, in the earlier lecture, I discussed about how to determine the speed from the performance chart.
Detailed Explanation
To determine push and backtrack times, you must know the travel or dozing distance and the speed of the machine. Speed can be directly influenced by resistance faced on the project site, which can be sourced from performance charts that detail how different conditions affect machine speed.
Examples & Analogies
Consider riding a bicycle on flat ground versus up a hill. The flat ground allows for faster speeds, while the hill slows you down. Similarly, understanding terrain resistance helps predict the bulldozer's actual speed.
Understanding Maneuver Time and Transmission Types
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So, now let us see what is this maneuver time?... The maneuver time will depend upon the type of transmission.
Detailed Explanation
Maneuver time varies depending on whether the bulldozer has direct transmission (manual gear change) or an automatic transmission (torque converter). Each type takes a different amount of time to adjust speeds, which in turn affects the overall cycle time of the bulldozer.
Examples & Analogies
Consider using a manual versus an automatic car. An automatic car allows for smoother transitions between speeds, often leading to faster driving times. The same principle applies to maneuvering a bulldozer based on its transmission type.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: A duration encompassing all operations on a bulldozer.
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Fixed Time: Time required for actions that remain constant regardless of distance.
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Variable Time: Time that changes depending on project-specific factors.
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Maneuver Time: Adjustments made by the operator affecting efficiency.
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Performance Chart: Tool for understanding bulldozer speed and resistance.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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A bulldozer operating on a flat terrain with a haul distance of 50 meters will need to adjust cycle time based on the specified speed.
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If a bulldozer switches from power shift to direct transmission, the fixed time will increase, affecting overall productivity.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Cycle time takes a while to measure, fixed time's a treasure, variable's the pleasure.
📖 Fascinating Stories
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Imagine a bulldozer at a construction site, always adjusting its gears. It takes consistent time to shift gears (fixed) and different times to push soil depending on the distance (variable), making it a smart worker in the field.
🧠 Other Memory Gems
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Use 'CVFM' to remember: C for Cycle time, V for Variable time, F for Fixed time, and M for Maneuvering time.
🎯 Super Acronyms
Remember 'R-G' for Rolling and Grade resistance, critical in using performance charts.
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 all operations involving a bulldozer, consisting of fixed and variable time.
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Term: Fixed Time
Definition:
The portion of cycle time that remains constant regardless of operational conditions.
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Term: Variable Time
Definition:
The portion of cycle time that varies depending on external factors such as haul distance and speed.
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Term: Maneuver Time
Definition:
The time taken to adjust the bulldozer's operation, including gear changes and acceleration, affecting overall efficiency.
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Term: Performance Chart
Definition:
Graphical representation of a bulldozer's speed versus its resistance, aiding in operational assessments.