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Interactive Audio Lesson
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Understanding Cycle Time
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Today, let's discuss the concept of cycle time in bulldozers. Can anyone tell me what cycle time includes?
Isn't it the total time it takes for a bulldozer to perform a complete dozing cycle?
Exactly, it encompasses the time spent pushing, backtracking, and maneuvering. We can remember this with the acronym 'PBM': Push, Backtrack, Maneuver.
So how does the haul distance affect the push time?
Great question! The push time increases linearly with haul distance. The longer the distance, the more time is required to complete the push.
And is the backtrack time similar?
Not exactly. While backtrack time is generally shorter since the bulldozer travels with an empty blade, it still depends on the distance. Let’s recap: Cycle time consists of Push, Backtrack, and Maneuver times.
Evaluating Productivity
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Now, let's talk about how we evaluate a bulldozer's productivity. Who can share how we measure it?
Is it based on the blade load and cycle time?
Exactly, productivity is calculated by dividing the blade load by the cycle time. It’s crucial to specify whether we’re measuring in the loose state or bank state.
What's the difference between those states?
The bank state refers to the material in its natural, undisturbed condition, while the loose state is when it's been excavated and disturbed. Both affect the productivity results.
Right! And with that, we use performance charts to find the speed based on resistance.
Perfect! Always remember that the performance chart is essential for determining speed under actual project conditions.
Using Production Curves
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Next, let’s delve into production curves. Who can explain what they are?
Are they graphs that show how productivity changes with different dozing distances?
Exactly! They illustrate the relationship of dozing distances versus productivity, and different lines on the graph correspond to various bulldozer models.
How do we use them in our calculations?
Great! You choose an ideal productivity value from the curve based on your dozing distance and then apply adjustment factors for specific site conditions.
What factors do we adjust for?
Factors such as operator skill level, material type, and terrain slope. Remember, the curves are based on standard conditions, so adjustments are crucial!
Calculating Actual Productivity
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Now that we understand production curves, let's look at calculating actual productivity. Who remembers how we start?
We first find the ideal value from the curve for our bulldozer model.
Correct! Then what do we do next?
We apply the correction factors based on our project specifics!
Indeed! This will give us the realistic productivity we can expect under actual working conditions. Always think of the ideal value as a starting point.
This sounds really important for estimating costs in projects!
Absolutely! Accurate productivity estimates lead to better budgeting and bidding strategies. Always strive to apply your adjustments thoughtfully.
Introduction & Overview
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Quick Overview
Standard
The section elaborates on defining and calculating cycle time, the relationship between haul distance and push time, and introduces the concept of production curves for estimating bulldozer productivity, including necessary corrections for project conditions.
Detailed
In construction and earthmoving operations, understanding and optimizing the cycle time of machines such as bulldozers is crucial for productivity. This section breaks down the cycle time into three key components: fixed time (maneuvering time), defined as the requisite time for speed adjustments or gear changes; variable times such as push time and backtrack time, influenced by haul distance and speed. The section also highlights the significance of the performance chart, which illustrates how speed correlates with total resistance on-site. Furthermore, productivity is derived through calculations involving the machine's blade load and cycle time, and adjustments must be made to account for project-specific efficiency. The concept of production curves is introduced as a method of estimating productivity utilizing manufacturer-provided graphs that relate dozing distance with expected output. The section emphasizes that such curves assume ideal conditions and necessitate corrections based on actual project parameters such as operator skill, material type, and terrain gradient. Hence, accurately estimating bulldozer productivity involves selecting values from production curves and adjusting them by applying correction factors reflective of operational realities.
Audio Book
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Cycle Time and Its Components
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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
Cycle time refers to the total time required for a bulldozer to complete one full operation cycle. This operation includes cutting the earth, pushing it to a designated area, dumping, and then returning to the starting position (backtracking). Understanding cycle time is vital because it directly affects the productivity of the bulldozer—the faster you can complete these operations, the more efficient the work is.
Examples & Analogies
Think of the bulldozer's cycle time like the time it takes to bake a batch of cookies. First, you need to prepare the dough (cutting), then place it in the oven (pushing), and finally take them out when they're cooked (dumping). Afterward, you may need to clean up and prepare for the next set, which is similar to backtracking. Just like in baking, the total time taken for all these processes will determine how quickly you can produce your cookies.
Fixed and Variable Times
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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
In the context of bulldozer operations, fixed time refers to the consistent time needed for tasks such as maneuvering (changing speed or gears), while variable time changes based on factors like haul distance. Push time and backtrack time are variable because the greater the distance that material needs to be pushed or returned, the more time it takes. This variation makes planning and estimating productivity essential for efficient operations.
Examples & Analogies
Imagine you are moving boxes from one room to another. If the room is close by, it takes only a minute to make a trip (fixed time for moving boxes). However, if that room is far away, each trip takes longer (variable time). Depending on how far away the room is, the total time to complete the task can significantly increase.
Determining Speed and Distance
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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. 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.
Detailed Explanation
To calculate the push and backtrack times, it is essential to know both the travel distance (how far the bulldozer has to move material) and the speed at which the bulldozer operates. The speed can often be derived from performance charts that indicate various factors affecting how quickly the bulldozer can operate under specific conditions.
Examples & Analogies
Think of driving a car. Before you can calculate how long a trip will take, you need to know how far you're going (the distance) and how fast you can drive (the speed). If you know you have to travel 60 miles and can drive at an average speed of 30 miles per hour, you can easily calculate that the trip will take about 2 hours.
Maneuver Time and Transmission 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 time it takes for the operator to change speeds or gears in the bulldozer. This time can be affected by the type of transmission—either a manual gear change (direct transmission) or an automatic system (torque converter). In general, automatic transmissions have shorter maneuver times because the system manages gear changes without operator input.
Examples & Analogies
Think about driving a manual versus an automatic car. When driving a manual, you need to physically change gears, which takes time and skill (longer maneuver time). In contrast, with an automatic car, the car takes care of shifting gears for you, allowing you to focus on the road and speed up quickly (shorter maneuver time).
Estimating Productivity
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Now let us see how to estimate the productivity of the bulldozer. So, we are going to estimate the productivity in loose 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
Productivity in earthmoving operations is typically measured in loose cubic meters per hour. It's important to specify the state of the material—whether loose (after being dug up) or in bank state (natural, undisturbed). Knowing the blade load (how much material can be moved at once) and the cycle time of the bulldozer (how long it takes to complete one cycle of operation) is crucial to calculating this productivity accurately.
Examples & Analogies
Think of a team of workers who are moving sand. If they're measuring how much sand they can move in an hour, they need to decide whether to count the loose sand (after it's dumped from a truck) or packed sand (in its natural compacted state). Just like how counting different states can yield different totals, estimating bulldozer productivity needs to consider how the material is measured.
Factors Affecting Productivity and Correction Factors
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These production curves are drawn based upon ideal conditions. What are all ideal conditions? It is drawn assuming 100% job efficiency, that means your machine is going to work for 60 minutes in a hour, so that is what is the assumption.
Detailed Explanation
Production curves represent ideal conditions, like assuming the bulldozer operates for the full hour without interruptions and under optimal conditions. In reality, factors such as machine efficiency, operator skill, soil type, and environmental conditions can all affect productivity. Adjusting estimates based on these factors ensures more realistic and applicable calculations.
Examples & Analogies
Imagine you have a perfect sewing machine that works flawlessly 100% of the time. This is a hypothetical situation. In reality, machines can jam, operators might take breaks, or certain materials might be harder to sew. Understanding that ideal conditions don't always exist helps us estimate more accurately in real-life scenarios, like predicting how long it will take to complete a large sewing order.
Using Production Curves for Estimation
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So, if you know your equipment model number, so refer to the appropriate equipment handbook look for the appropriate model number and choose a production value directly. So, if you know the dozing distance, say the dozing distance is 60 meter and the model number is say F. So, you can directly calculate the production value.
Detailed Explanation
Manufacturers often provide production curves that allow operators to determine productivity based on the specific model of the bulldozer and the dozing distance. By using these curves, estimators can select corresponding production values instantly, saving time on calculations. However, actual operating conditions must be applied to these ideal values to ensure accuracy.
Examples & Analogies
Consider a recipe book that gives you baking times based on specific oven types and conditions. If you're using a similar oven, you can trust the times given. But if your oven has quirks or extra heat, you may need to adjust times. Similarly, while the production curves offer good estimates, the estimator must consider actual site conditions.
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 duration required for a dozer to execute a full dozing operation.
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Production Curves: Graphical tools that aid in predicting productivity based on operational parameters.
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Correction Factors: Adjustments made to ideal values from production curves to account for varying project 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 6 minutes to push and 3 minutes to backtrack, with 2 minutes for maneuvering, the cycle time would be 11 minutes.
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Using a performance chart, if the speed estimated is 5m/min with a push distance of 30m, the push time would be 6 minutes for that operation.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Maneuver, backtrack, push away, Cycle time is here to stay!
📖 Fascinating Stories
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Imagine a bulldozer pushing soil to build a road. Each time it travels forward, it pushes the dirt, then rolls back empty, adjusting gear as it advances again—illustrating cycle time in action.
🧠 Other Memory Gems
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Remember 'PBM' for cycle time: Push, Backtrack, Maneuver.
🎯 Super Acronyms
For estimating productivity, think ‘PCD’ — Production Curves and Distances.
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 cycle of operation for a bulldozer, including push time, backtrack time, and maneuver time.
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Term: Flex Time
Definition:
Time variable depending on operational conditions, such as haul distance.
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Term: Performance Chart
Definition:
A graphical representation of the relationship between speed and resistance for different operational conditions for a machine.
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Term: Production Curves
Definition:
Graphs that show the expected productivity of a bulldozer relative to its dozing distance.
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Term: Correction Factors
Definition:
Adjustments made to ideal productivity values based on actual project site conditions to yield realistic estimates.
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Term: Job Efficiency
Definition:
The actual operational time a machine can work effectively, usually expressed as a percentage of total time.