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A short class with Sarah and her students. The other ways are under More.
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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!
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.
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!
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!
Cycle Time - Total time needed for one complete bulldozer cycle.
Blade Load - Volume of material that can be moved by the bulldozer.
Maneuver Time - Time taken to adjust gears and speeds.
Job Efficiency - Effective operation time compared to total time.
Performance Chart - Tool for determining machine speed based on resistance.
Production Curves - Graphical tool to estimate productivity based on parameters.
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.
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.
For dozers to cut, and push, and track, Time is key, don't hold back!
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.
To remember cycle time's parts: C (Cutting), P (Pushing), D (Dumping), R (Returning), M (Maneuvering) – 'CPDRM'.
Use 'CPB' for Cycle Time (C), Productive Load (P), and Blade Load (B).
Term
What is Cycle Time?
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Term
Define Blade Load.
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What is Maneuver Time?
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Explain Job Efficiency.
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The total time required to complete one full operation cycle of a bulldozer, encompassing cutting, pushing, dumping, and returning.
The amount of material a bulldozer can effectively move or push, usually measured in loose cubic meters.
The fixed time contributed to the overall cycle time for gear changes and adjustments in operation speed.
The ratio of actual operating time to the total time available in one hour, affecting productivity calculations.
A graphical representation used to determine appropriate speed based on project-specific conditions and total resistance.
Graphs that illustrate the expected productivity of bulldozers based on different operational parameters, such as dozing distances.
This section discusses the concepts of cycle time and blade load for bulldozers, emphasizing their significance in estimating productivity.
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.
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.