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Interactive Audio Lesson
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Understanding Cycle Time
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Today, we're going to discuss cycle time. Can anyone tell me what cycle time refers to in bulldozer operations?
Is it the total time taken to complete one cycle of work?
Exactly! Cycle time includes the time for cutting, pushing, dumping, returning, and maneuvering. It's crucial for determining productivity.
What part of the cycle time is fixed and variable?
Great question! Fixed time involves maneuvering, while variable time depends on haul distance and speed. Remember, speed can change based on terrain conditions!
How does the speed actually get determined?
Speed is determined using performance charts that consider total resistance on the project site. This is a key factor for calculating push time!
So if the terrain is tough, the speed decreases, right?
Exactly! Remember, the tougher the terrain, the more time it takes to push or return. Great discussion!
Components of Blade Load and Productivity
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Now let’s talk about blade load. Can someone tell me what it is?
Isn't it how much material the bulldozer can move at once?
Correct! It’s typically expressed in loose cubic meters. We get blade load from either the manufacturer's specs or field measurements.
And how do we use blade load to calculate productivity?
You divide the blade load by the cycle time! So, productivity equals blade load divided by cycle time. Remember to consider the state of the material!
What about the job efficiency? How does that fit in?
Job efficiency indicates how many minutes the machine operates in an hour. You’ll typically multiply your productivity by this efficiency to get a realistic figure.
Does this mean if my machine operates for only 30 minutes, I should adjust my productivity in that time frame?
Exactly! Never assume a bulldozer operates the entire hour for optimal estimations.
Maneuvering Time and Conditions
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Next, let's discuss maneuvering time! Who can describe what it entails?
Is it the time taken to change speed and gears?
That’s correct! The type of transmission also greatly influences this time.
What’s the difference between direct transmission and power shift?
Power shift has automatic gear changes whereas direct transmission requires manual changes, which increases maneuver time!
Does maneuver time affect overall cycle time significantly?
Yes! Particularly when estimating productivity, it can make a notable difference.
So if I know my machine’s transmission type, I can calculate maneuver time correctly?
Absolutely! Understanding these details leads to more accurate estimates. Well done, everyone!
Using Production Curves and Correction Factors
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Let's integrate what we've learned and explore production curves. What are they used for?
They show the relationship between dozing distance and productivity!
Exactly! And what must you consider when using these curves?
We need to apply correction factors based on project conditions, such as soil density and operator skill.
Right! Without these adjustments, our productivity estimates could be incorrect.
Can you give us an example of how these correction factors work?
Certainly! If your equipment is operating in worse conditions—like on a slope—the productivity will decrease, and you'd need to adjust accordingly using the coefficients.
So if I'm operating a bulldozer uphill, I should expect lower productivity compared to moving downhill?
Yes! Being aware of these nuances is crucial for accurate calculations and effective project planning!
Introduction & Overview
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Quick Overview
Standard
The section elaborates on the process of calculating the cycle time and blade load for bulldozers, detailing the components that affect these calculations such as haul distance, speed, maneuvering time, and production conditions. It includes the importance of estimating productivity for earthmoving operations.
Detailed
Detailed Summary
The section focuses on calculating the key metrics involved in bulldozer operations, specifically cycle time and blade load.
- Cycle Time Explained: Cycle time is the total time taken for a bulldozer to perform a complete work cycle, which includes cutting, pushing, dumping, returning, and maneuvering. It consists of both fixed and variable times. The fixed time accounts for the maneuver time (changing speed and gears), while variable time is influenced by haul distance and speed.
- Maneuvering Factors: Depending on the type of transmission, maneuver time can vary significantly. Power-shift models (automatic gear change) have shorter maneuver times of about 3 seconds compared to 6 seconds for manual gears. This affects the overall cycle time, which needs to be accurately estimated to evaluate productivity.
- Calculating Push and Backtrack Time: To determine push and backtrack times, knowing travel distances and machine speed is essential. The speed can be derived from performance charts based on project-specific conditions like total resistance and terrain type.
- Blade Load and Productivity: Blade load refers to the material that the bulldozer can move, calculated based on the blade capacity. Productivity is expressed in loose cubic meters per hour and is given by the formula: Productivity = Blade Load / Cycle Time. Additionally, it's important to express productivity accurately, considering factors like material state (loose vs. bank).
- Estimating Cost and Efficiency: Job efficiency must also be factored into the productivity estimate, indicating the operational time per hour.
- Finally, correction factors based on project conditions, machine type, and operator skill are necessary for calculating realistic productivity values, enhancing accuracy for project bidding and operational planning.
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 refers to the total time taken for the bulldozer to complete one full operation cycle. This includes the time to push earth, backtrack to the starting position, and maneuver into the correct position for the next push. Understanding cycle time is crucial for estimating the efficiency and productivity of the bulldozer during earthmoving tasks.
Examples & Analogies
Think of a bulldozer's cycle time like a runner completing a lap. The runner has to run to a point (push the earth), return to the start (backtrack), and then adjust their position to start the next lap (maneuver). The total time for this entire process is similar to the cycle time of the bulldozer.
Fixed and 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. Because it is variable depending upon your haul distance.
Detailed Explanation
In calculating cycle time, we differentiate between fixed time and variable time. Fixed time includes the consistent time requirements for maneuvering the bulldozer. Variable time, however, changes based on the haul distance, which is the distance the bulldozer has to push the dirt. Longer distances mean longer push times and backtrack times.
Examples & Analogies
Imagine a taxi driver who always takes 10 minutes to get the car ready (fixed time) but takes variable time to reach a destination depending on how far away it is. Similarly, the bulldozer has consistent and variable times that affect how quickly it can complete its tasks.
Determining Push 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.
Detailed Explanation
To calculate push time, we need to know both the distance the bulldozer will push material and the speed at which it will move. The formula for push time typically involves the relationship between speed and distance. The further the dozing distance, the longer the push time will be.
Examples & Analogies
Consider a person pushing a shopping cart down an aisle. The further they have to push the cart, the longer it will take them based on their speed. The same applies to the bulldozer - more distance equals more time spent pushing.
Speed Determination
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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
To understand how fast the bulldozer can push, we refer to a performance chart that provides speeds under various conditions. Knowing the terrain, rolling resistance, and grade resistance allows us to calculate the operating speed of the bulldozer, which is crucial for accurate cycle time and productivity estimations.
Examples & Analogies
Think of a bicycle rider adjusting their speed depending on the slope of the road. If the road is flat, they can go faster, while uphill slows them down. The bulldozer’s speed varies similarly based on the site conditions.
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.
Detailed Explanation
Maneuver time is the period required for adjustments in operation, such as changing gears or accelerating. This time can vary greatly depending on whether the bulldozer uses manual gear changes or an automatic system. Understanding this is important for accurate cycle time calculations since different types of transmissions will yield different maneuver times.
Examples & Analogies
Imagine a driver in a manual car versus an automatic. The manual driver takes extra time to shift gears at the right moments, while the automatic system does it quickly and efficiently. Similarly, the bulldozer's maneuver time is influenced by its transmission type.
Impact of Transmission on Maneuver Time
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Depending upon this transmission mode, your maneuver time will change. Say if you are going to go for power shift that is automatic gear change, the maneuver time is 0.05-minute.
Detailed Explanation
The type of transmission directly affects maneuver time. For example, power shift transmissions (automatic) allow for quicker adjustments than manual ones. This difference is quantified in terms of minutes, significantly impacting the overall efficiency and cycle time of operations.
Examples & Analogies
Think of a vending machine. An automatic one quickly delivers a drink with the push of a button, while a manual machine requires more steps to get the same item. The bulldozer operates similarly, with automatic transmissions doing the job faster.
Considering Job Efficiency in Productivity Estimation
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So, after estimating this, you have to take into account the job efficiency.
Detailed Explanation
Job efficiency takes into account that the bulldozer will not operate at full capacity for the entire duration. This means estimating how long the machine can effectively work within an hour. The efficiency ratio must be factored into productivity calculations to provide a realistic output estimation.
Examples & Analogies
Just like a student might not study non-stop for an hour and instead take breaks, the bulldozer won't be working every moment of its hour due to possible delays or inefficiencies.
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.
Detailed Explanation
Unit cost of production refers to the expenses associated with moving a cubic meter of earth. This requires knowing the a) the hourly cost of operating the bulldozer and b) the productivity during that hour. With both figures, we can determine a cost-effective operation.
Examples & Analogies
Imagine a pizza shop that knows how much it costs to make one pizza and how many pizzas it can make in an hour. By dividing the costs by the output, they can set a price that covers their expenses.
Estimation Techniques
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So, what we discussed is one way of estimating the productivity. So, for that you need the information on the blade capacity and you need the information of the haul distance and you need the information on the rolling resistance and grade resistance.
Detailed Explanation
To estimate productivity, one method involves knowing the bulldozer's blade capacity, haul distance, and site conditions like rolling resistance. These factors determine how quickly and efficiently the bulldozer can perform its tasks. Combining these with correction factors will yield the actual productivity rate.
Examples & Analogies
Think of baking cookies. The capacity of your oven, the distance and time you bake, and the ingredients play a role in determining how many cookies you can produce. In the same way, the bulldozer's various performance features and external conditions determine how productive it can be.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time - Total time needed for one complete bulldozer cycle.
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Blade Load - Volume of material that can be moved by the bulldozer.
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Maneuver Time - Time taken to adjust gears and speeds.
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Job Efficiency - Effective operation time compared to total time.
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Performance Chart - Tool for determining machine speed based on resistance.
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Production Curves - Graphical tool to estimate productivity based on parameters.
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 with a blade load of 5 cubic meters spends 10 seconds pushing dirt and 5 seconds returning, totaling a cycle time of 15 seconds.
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If the blade load is 10 cubic meters and the cycle time is 20 seconds, the productivity would be calculated as 10 / (20/3600) = 1800 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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For dozers to cut, and push, and track, Time is key, don't hold back!
📖 Fascinating Stories
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Imagine a bulldozer named Benny. Every day, he cuts and pushes dirt, but Benny never forgets to check his cycle time, ensuring he's efficient and fast, just like his friend the speedy rabbit on the construction site.
🧠 Other Memory Gems
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To remember cycle time's parts: C (Cutting), P (Pushing), D (Dumping), R (Returning), M (Maneuvering) – 'CPDRM'.
🎯 Super Acronyms
Use 'CPB' for Cycle Time (C), Productive Load (P), and Blade Load (B).
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 required to complete one full operation cycle of a bulldozer, encompassing cutting, pushing, dumping, and returning.
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Term: Blade Load
Definition:
The amount of material a bulldozer can effectively move or push, usually measured in loose cubic meters.
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Term: Maneuver Time
Definition:
The fixed time contributed to the overall cycle time for gear changes and adjustments in operation speed.
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Term: Job Efficiency
Definition:
The ratio of actual operating time to the total time available in one hour, affecting productivity calculations.
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Term: Performance Chart
Definition:
A graphical representation used to determine appropriate speed based on project-specific conditions and total resistance.
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Term: Production Curves
Definition:
Graphs that illustrate the expected productivity of bulldozers based on different operational parameters, such as dozing distances.