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Interactive Audio Lesson
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Understanding Cycle Time
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Today we're going to understand the cycle time of a bulldozer. Cycle time comprises push time, backtrack time, and maneuver time. Can anyone tell me what push time means?
Is it the time taken to push the material forward?
Exactly! Push time varies based on haul distance and the speed of the machine. Now, what about backtrack time?
Is that when the bulldozer returns to its starting point?
Correct! It’s typically less than push time since the bulldozer travels empty. Good job! Let's remember: 'P for Push and B for Backtrack.' It helps to recall their sequence.
Factors Affecting Maneuver Time
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Next, let’s consider maneuver time. This time is affected by how the bulldozer changes gears. What two types of transmission are there?
There’s manual gear change and automatic gear change?
Right! The choice affects maneuver time: 0.05 minutes for automatic and 0.1 minutes for manual. Can anyone remember the mnemonic for this?
I think it’s ‘Auto = Fast, Manual = Slow’ to help remember the differences!
Great memory! Remembering these nuances is key to understanding bulldozer productivity.
Calculating Productivity
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Now, let’s calculate productivity. It’s defined as blade load divided by total cycle time. What factors influence this calculation?
I think the haul distance and speed of the machine are important?
And the job efficiency factor too, right? The machine won’t be working the entire hour.
Exactly! Adjusting for work efficiency is crucial for accurate estimates. Can someone give an example?
If a bulldozer works for 45 minutes, it means the efficiency is 45/60 or 0.75!
Well done! So, productivity estimation is critical for efficient project management.
Cost Estimation and Its Importance
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Finally, let’s discuss cost estimation. Why do you think it's important in bidding?
So we can quote a fair price and not lose money during the project?
Exactly! Knowing unit costs helps plan effectively. What’s the formula to find the unit cost of production?
It's the hourly cost divided by hourly productivity!
Perfect! Always remember to evaluate costs thoroughly to avoid unfortunate miscalculations.
Introduction & Overview
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Quick Overview
Standard
In this section, we delve into the components of bulldozer productivity, including cycle time, push and backtrack times, maneuvering, and how to calculate these based on operational conditions and efficiency factors. It highlights the importance of accurate estimations for effective project management.
Detailed
Estimating Productivity of the Bulldozer
In this section, we detail the critical elements involved in estimating bulldozer productivity, defined primarily in terms of loose cubic meters per hour. The bulldozer’s cycle time encapsulates various components such as push time, backtrack time, and maneuver time, each significantly influenced by the haul distance and machine speed.
Key concepts include:
1. Cycle Time: The total time taken for the bulldozer to perform its work cycle, which includes:
- Push Time: The time spent pushing material, which varies based on haul distance and machine speed.
- Backtrack Time: The return journey, generally shorter than push time due to the mixed load conditions.
- Maneuver Time: Dependent on gear changes, influenced by the type of transmission used, either direct or automatic.
2. Working Efficiency: Not all hour time is productive; efficiency must be accounted for to reflect actual work runtime.
3. Productivity Calculation: It involves determining blade load from the manufacturer's specifications or field measurements and calculating cycle time to derive productivity.
4. Job Efficiency and Cost Estimation: Drafting accurate estimates is critical for project bidding and cost management, incorporating job efficiency factors to adapt estimates to actual site conditions.
5. Alternative Estimation Methods: Thumb rules and production curves are highlighted as quick methods to estimate productivity based on horsepower and other operational metrics, requiring adjustments to account for real-world conditions.
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 the bulldozer is a crucial measure that includes all the actions the bulldozer performs during a single complete operation. This involves three main activities: cutting the earth, pushing it to the desired location, and then returning to the starting point (backtracking) to repeat the operation. The combined duration of these activities defines the cycle time, which is a vital metric for estimating productivity.
Examples & Analogies
Imagine using a shovel to dig soil, load it into a wheelbarrow, and then push the wheelbarrow to a location to dump the soil. After dumping, you return to start the process again. Just like in this scenario, the time it takes to complete all these actions with the bulldozer equates to the cycle time.
Fixed 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, 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. 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
Cycle time comprises fixed and variable elements. The fixed time relates to maneuvering, which is mostly constant, while the variable time corresponds to the push and backtrack stages, which fluctuate based on the haul distance. The longer the distance the bulldozer has to move material, the greater the push and backtrack times. Additionally, these times can also vary depending on the speed at which the bulldozer operates.
Examples & Analogies
Think about driving a car to deliver packages. If you have to drive 5 miles, it will take you a certain amount of time to reach the destination (variable, based on distance). However, regardless of the distance, you will spend some time at traffic lights and stop signs (fixed). The total time is the sum of both the variable and fixed times.
Determining Speed
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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. So, you very well know how to determine the speed. So, in the earlier lecture, I discussed about how to determine the speed from the performance chart.
Detailed Explanation
In order to calculate push time and backtrack time, two critical factors need to be established: the travel or haul distance, and the speed of the bulldozer. The speed can be determined using a performance chart, which relates the speed to the resistance faced by the bulldozer in a given operational environment.
Examples & Analogies
Using a bicycle as an analogy, to estimate how long it will take to reach a destination, you would first measure the distance to your destination and then know your cycling speed. With this information, you can easily calculate the time needed to get there.
Maneuver Time and Its Types
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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 refers to the period it takes for the bulldozer to adjust its speed or change gears during operations. This time is influenced by the type of transmission system used: either direct (manual shifting) or automatic (power-shift). Each type has different time requirements for changing gears, which directly affects overall cycle time.
Examples & Analogies
Consider editing a document on your computer: if you have to press a lot of buttons to change formatting manually (direct transmission), it'll take longer than if you had a smart format tool that instantly handles changes for you (automatic transmission).
Estimating Bulldozer Productivity
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So, 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
To estimate a bulldozer's productivity, the output needs to be measured in loose cubic meters per hour. It is crucial to clarify whether this measurement is of loose material (as dug) or in its bank state (natural state before digging). Understanding this distinction helps in accurately conveying the bulldozer's productivity.
Examples & Analogies
Consider measuring how much flour you have before and after sifting: the volume of flakes observed after sifting (loose state) differs from tightly packed flour in its original bag (bank state). Knowing which state you're measuring can change the way you comprehend the quantity.
Calculating Blade Load and Cycle Time Components
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So, it is nothing but your blade load divided by the cycle time. So, how to determine the blade load just now we discussed. So, you can get it from the manufacturer, what is the blade capacity or from your own past experience you can get it. Or you can do the field measurement yourself and find the dimension of the pile of material lying in front of the blade and determine the blade capacity.
Detailed Explanation
Bulldozer productivity can be calculated by dividing blade load (the capacity of the bulldozer's blade to carry material) by the cycle time (the total time taken for one complete operation). Blade load can be determined from manufacturer specifications, previous field experience, or by measuring the pile of material directly.
Examples & Analogies
Think of it as trying to fill a bucket (blade load) in a well (cycle time). The more efficiently you can fill that bucket and haul it up (shorter cycle time), the better productivity you have.
Job Efficiency and Working Time
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So, after estimating this, you have to take into account the job efficiency. So, one thing you should know that your machine is not going to be operated for the entire 60 minutes in an hour. So, depending upon your project condition, it may operate for 45 minutes or 50 minutes. So, it may even operate only for 30 minutes, it depends upon your project condition.
Detailed Explanation
When estimating productivity, it is vital to consider job efficiency, which accounts for the actual time the machine operates within an hour. This realized time may vary based on project conditions and can be less than 60 minutes, impacting the overall productivity calculation. Hence, the effective working time must be considered while performing calculations.
Examples & Analogies
If you are completing homework and spend some time getting distracted (similar to operational downtime), you won't be able to finish all the questions in one hour. Your actual 'working' time is less than that hour, just like a bulldozer may not work continuously throughout its scheduled time.
Unit Cost of Production
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This is a very important because as I told you, when you prepare for bidding when you plan for bidding in unit rate work, in unit rate contract unit rate work. We are very much interested in this data, what is the unit cost associated with every activity, unit cost of earthmoving operation.
Detailed Explanation
Understanding the unit cost of production is key, especially when preparing for bidding on contracts. This involves calculating costs related to operating the bulldozer per unit volume of material moved (e.g., per loose cubic meter). This financial context aids decision-making and helps in providing accurate bid estimates.
Examples & Analogies
Imagine planning a catering service: you need to know how much each dish costs to prepare in order to estimate your total costs and price your services correctly. Just as in catering, accurately estimating production costs for earthmoving is crucial for effective business planning.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: Sum of push time, backtrack time, and maneuver time, crucial for calculating productivity.
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Job Efficiency: The effective operational time of the bulldozer within an hour, important for realistic productivity estimates.
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 has a push time of 5 minutes, backtrack time of 3 minutes, and maneuver time of 1 minute, its cycle time is 9 minutes.
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Using an average efficiency of 0.8, if the productivity is calculated at 30 loose cubic meters per hour, the effective output would be 30 * 0.8 = 24 loose 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, then maneuver right, cycle time together, keeps productivity in sight.
📖 Fascinating Stories
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Imagine a bulldozer racing against time. It pushes heavy dirt, takes a swift backtrack, and adjusts gears to keep going.
🧠 Other Memory Gems
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PBM - Push, Backtrack, Maneuver; remember the order for cycle time.
🎯 Super Acronyms
C for Cycle, P for Push, B for Backtrack, M for Maneuver - all parts of time!
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Cycle Time
Definition:
The total time taken for a bulldozer to complete its work cycle, including push time, backtrack time, and maneuver time.
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Term: Push Time
Definition:
The time spent pushing material forward by the bulldozer, influenced by haul distance and speed.
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Term: Backtrack Time
Definition:
The return journey of the bulldozer after pushing material, generally shorter than push time.
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Term: Maneuver Time
Definition:
Time required for the bulldozer to change gears and adjust speed, affected by transmission type.
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Term: Job Efficiency
Definition:
The actual time the bulldozer operates effectively within an hour, typically less than 60 minutes.
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Term: Blade Load
Definition:
The amount of material the bulldozer blade can carry at one time.
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Term: Unit Cost of Production
Definition:
The cost associated with moving a unit volume of material, calculated as hourly cost divided by hourly productivity.