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Interactive Audio Lesson
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Understanding Cycle Time
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Today, we will explore the concept of cycle time in bulldozer operations. Cycle time consists of the time taken to push material, backtrack, and maneuver the machine. Can anyone tell me what they believe is cycle time?
Isn't it the total time needed for a bulldozer to complete one full operation?
Precisely! And what factors do you think influence cycle time?
I think the distance the bulldozer needs to push the earth affects it.
And also the speed, right?
Exactly! The farther you have to push, the longer cycle time, and your speed affects how quickly you can do that. Remember, we can categorize cycle time into push time, backtrack time, and maneuver time.
What's the difference between push time and backtrack time?
Great question! Push time is the duration spent pushing material, whereas backtrack time is when you return to the starting point, which usually takes less time since the blade isn't loaded. Let's move on to how we calculate these times. Remember, push and backtrack times are variable based on distance!
In summary, we discussed cycle time, which includes three components: push time, backtrack time, and maneuver time. Push time depends on haul distance and speed. Next, we'll explore job efficiency.
Job Efficiency
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Now, let's delve into job efficiency. What do you understand by this term?
Is it the time the machine spends actually working compared to the total available time?
Exactly! Job efficiency is the actual working time of the bulldozer during an hour, which can be much less than 60 minutes. Why do you think this matters?
It probably affects productivity calculations.
Correct! For accurate productivity estimates, we need to know job efficiency and multiply it with the calculated productivity. If, for instance, the bulldozer only works efficiently for 45 minutes in an hour, that will influence our final estimates.
So if we say job efficiency is 50 minutes, we'd take 50/60 to find that factor?
Spot on! Always divide the efficient working time by 60 to find your efficiency factor. Summary of what we learned: Job efficiency is actual working time in comparison to total time, crucial for productivity calculations.
Calculating Productivity
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Let's discuss how we calculate the productivity of a bulldozer. Can anyone mention the factors we need to consider?
We need to consider the blade load and the cycle time.
That's right! Productivity can be calculated using the formula: productivity = blade load / cycle time. But what defines blade load?
I believe blade load is the amount of material the bulldozer can push.
Exactly! You can find this information from the manufacturer or through past experience. Now, what about cycle time? How do we find that?
We need to calculate push, backtrack, and maneuver times?
Yes, and remember push and backtrack are variable time depending on haul distance and speed. Next, we’ll review how to calculate speed using performance charts.
In summary, we learned productivity of bulldozers depends on blade load and cycle time, while cycle time is made up of push time, backtrack time, and maneuver time.
Utilizing Production Curves
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Lastly, let’s discuss how we can utilize production curves to estimate productivity. Do any of you know what these curves represent?
They show the relationship between dozing distance and productivity?
Correct! Manufacturers provide these curves based on ideal conditions. Can anyone tell me what we need to apply when using them?
We need to account for real conditions and apply correction factors?
Exactly! You will apply correction factors based on operator skill, material type, visibility, and slope conditions. Always refer to the handbook for specific values or factors.
So if we pull a productivity value from the curve, we can adjust it with our project condition factors?
Right! Ensuring accurate estimates is key for project planning. To summarize, production curves are used to estimate productivity, adjusted with correction factors based on real project conditions.
Introduction & Overview
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Quick Overview
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The section covers essential concepts such as cycle time, which comprises push and backtrack times, and maneuver time, both of which impact the bulldozer's productivity. It explains how these times vary based on haul distance and machine operation. The importance of calculating job efficiency and various methods to estimate productivity using production curves, performance charts, and thumb rules are also discussed.
Detailed
Detailed Summary
In this section, we explore various aspects of job efficiency and operating time relevant to bulldozer operations. The primary focus is on cycle time, which includes:
- Push Time: The period spent pushing material, which is influenced by haul (or dozing) distance and machine speed.
- Backtrack Time: The time taken for the bulldozer to return to its original position, typically less than push time since the blade is empty during this phase.
- Maneuver Time: This time is affected by the mode of gear transmission (manual vs. automatic) and actually varies according to the adjustments made by the operator (e.g., changing gears).
The distinction between fixed time and variable time is crucial, with the variable time calculated as dependent on haul distance - longer distances result in more time spent pushing and backing. The section emphasizes the significance of job efficiency, which refers to the actual operating time of the bulldozer per hour (often less than 60 minutes for real tasks).
To estimate productivity effectively, a thorough understanding of the equipment, job conditions, and efficiency factors is vital. This could involve using detailed performance charts, knowing the machine's resistance under differing conditions, or employing thumb rules. The section concludes with methods for calculating unit costs for earthmoving operations, essential for project bidding and proper financial planning.
Audio Book
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Cycle Time of the Bulldozer
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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. 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
The cycle time of a bulldozer is the total time it takes to complete one operational loop, which includes cutting, pushing, and returning. This time is crucial for calculating how efficiently the bulldozer can work. In essence, every time the machine cuts the earth, pushes it to a dump site, and then returns to start over again, it completes a cycle. Understanding cycle time helps in planning and optimizing operations.
Examples & Analogies
Imagine a chef making a pizza. First, they prepare the dough (cutting), then spread the sauce and toppings (pushing), and finally, they put it in the oven (dumping). Once baked, they retrieve the pizza from the oven and clean the area for the next pizza (backtracking). The entire process is similar to the bulldozer's cycle time.
Fixed vs. Variable 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, so the time needed for changing the gear, all those things comes under the maneuvering. 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?
Detailed Explanation
Maneuver time is considered fixed because it involves the time taken for specific adjustments like changing speeds or gears. In contrast, push time and backtrack time are variable; they depend on the distance being traveled. For example, if the distance to the dump site increases, the push time increases, making it a variable factor in the overall cycle time.
Examples & Analogies
Think of driving a car. The time it takes to change gears (maneuvering) is relatively consistent regardless of how far you drive. However, if you drive to a location that's far away versus one that's close, the driving time varies depending on the distance, which parallels the variable push and backtrack times.
Calculating Push 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. So, this is solely dependent upon your haul distance, so this is dependent upon your haul distance, so that is why we call it as variable obviously it depends upon the speed also.
Detailed Explanation
The formula for calculating the time needed to push or backtrack a bulldozer is directly linked to the haul distance and the speed of the machine. Essentially, a longer distance means we'll spend more time pushing the load and coming back. The machine's operational speed also influences how long these tasks will take, meaning both haul distance and speed are crucial to accurately determining time.
Examples & Analogies
Imagine walking a dog. If you have a small yard, it takes just a few minutes to walk around, but if you take your dog to a large park, you'll spend significantly more time walking back and forth. Similarly, longer haul distances mean more time for bulldozer operations.
Understanding Maneuver Time
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So, now let us see what is this maneuver time? 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 involves the adjustments made by the operator for speed and gear changes. This time can vary based on the type of transmission the bulldozer uses—manual or automatic. Manual gear changes might take longer as the operator must physically shift gears, while automatic systems handle these changes more efficiently, resulting in shorter maneuver times.
Examples & Analogies
Consider a bike with manual gears versus an automatic bike. Changing gears in a manual bike requires more attention and takes longer compared to an automatic bike where the gears shift seamlessly. This makes the bike with an automatic transmission quicker in response, much like bulldozers operated with automatic transmissions.
Estimation of Productivity
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So, 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 bulldozer productivity involves calculating how much material can be moved in a specified timeframe, typically loose cubic meters per hour. It's crucial to specify whether you refer to loose material (after excavation) or bank material (before excavation) since each has different implications for productivity calculations.
Examples & Analogies
When filling a bag with flour, the amount it holds depends on how packed it is. A loosely filled bag has less weight than a tightly packed one. Similarly, distinguishing between loose and bank state in earthmoving operations affects productivity estimates.
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 time for one complete bulldozer operational cycle.
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Push Time: Duration spent pushing material during operation.
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Backtrack Time: Time spent returning to the base location after the push.
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Maneuver Time: Time taken to adjust speed or gears during operation.
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Job Efficiency: The percentage of time the bulldozer effectively works in relation to the total time.
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Blade Load: The quantity of material pushed by the bulldozer in a cycle.
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Production Curves: Graphs depicting productivity as a function of dozing distance.
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Correction Factors: Adjustments applied to productivity estimates based on real working conditions.
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 bulldozer takes 10 minutes to push material 40 meters and 5 minutes to backtrack, then the cycle time is 15 minutes. If it operates at 50% efficiency for 60 minutes, the job efficiency would be 30 minutes.
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A bulldozer with a blade load capacity of 2 cubic meters and a cycle time of 30 minutes would have a productivity of 4 cubic meters per hour.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Push and backtrack, in time we learn, Maneuver quick, for productivity we yearn.
📖 Fascinating Stories
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Imagine a bulldozer named Bud, who was always in a rush. He quickly pushed soil, then backtracked with great control, adjusting his path to become the master of efficiency.
🧠 Other Memory Gems
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Remember 'PBM' - Push, Backtrack, Maneuver for the components of cycle time.
🎯 Super Acronyms
Use 'JET' for Job Efficiency Time to remind you of the actual working minutes over available minutes.
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 by the bulldozer to complete one full operational cycle, including push time, backtrack time, and maneuver time.
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Term: Push Time
Definition:
The time taken by the bulldozer to push material to the designated location.
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Term: Backtrack Time
Definition:
The time taken for the bulldozer to return to its starting position after unloading material.
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Term: Maneuver Time
Definition:
The duration needed for the operator to change speed or gears during bulldozer operation.
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Term: Job Efficiency
Definition:
The ratio of the actual working time of the bulldozer to the total available time in an hour.
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Term: Blade Load
Definition:
The amount of material the bulldozer is capable of pushing in one cycle.
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Term: Production Curves
Definition:
Graphs representing the relationship between dozing distance and productivity under ideal conditions.
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Term: Correction Factors
Definition:
Adjustments made to account for real working conditions that differ from the ideal conditions represented in production curves.