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A short class with Sarah and her students. The other ways are under More.
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Today, we are going to discuss the cycle time of a bulldozer. Can anyone tell me what cycle time consists of?
Is it the time it takes to push earth and come back?
Exactly, Student_1! The cycle time includes cutting, pushing the earth, backtracking, and maneuvering. Let's break it down for clarity. The pushing and backtracking times are variable. Can you see why?
Because it depends on the distance we're pushing the earth?
Correct! The haul distance directly impacts these times. Now, can anyone guess what fixed time refers to in this context?
Is it the time taken for maneuvering operations, like changing gears?
Yes, great job, Student_3! Let's remember: Fixed time is your maneuver time, which includes gear changes and speed adjustments. Keep this in mind when estimating productivity!
Now that we know the cycle time components, what factors do you think can affect push time and backtrack time?
The speed of the bulldozer?
Exactly, Student_4! If the speed increases, the time decreases. And what determines how we calculate this speed?
The performance chart!
Yes, precisely! The performance chart lets us see how speed varies with resistance. Remember, resistance includes rolling resistance from terrain and grade resistance from sloping.
So, if the terrain is hilly, the speed will decrease?
Correct! Increased resistance leads to reduced speed, affecting cycle time. Let's take a moment to summarize: both haul distance and speed are crucial for calculating total cycle time.
In our discussion on productivity, we need to calculate it in terms of loose cubic meters per hour. Can anyone tell me how we arrive at this number?
By dividing the blade load by the cycle time?
Exactly right! The blade load is critical. Where do we even obtain the blade load from?
From the manufacturer or past field measurements!
That's correct! Excellent work. Keep in mind, after calculating the productivity we must consider job efficiency—how much time the bulldozer is actually operational versus downtime. Can anyone explain how that affects our calculations?
If the machine operates only 40 minutes in an hour, we need to multiply the productivity by that time's fraction?
Correct, Student_2! Always remember to adjust for job efficiency when making your productivity estimates. This is a key aspect!
Composed of cutting, pushing, backtracking, and maneuvering times.
Time for pushing and backtracking which depends on haul distance.
Time related to maneuvering, which is more consistent across operations.
Blade load divided by cycle time.
Cut, push, backtrack, then maneuver with ease, cycle time’s made simple, just remember these!
Imagine a bulldozer named Bob, who cuts earth all day. Bob pushes dirt, then takes a back trip after each play. Bob changes gears when the load gets tough, but he knows it’s the cycle time that matters the most!
P B M C - Push, Backtrack, Maneuver, Cycle - helps remember the key components of bulldozer cycle time.
PBMC - Push, Backtrack, Maneuver, Cycle Time.
Term
What is cycle time?
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Term
Define push time.
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The total time taken to complete a cycle of operations including cutting, pushing, backtracking, and maneuvering.
Variable time taken to push earth to a designated dump location.
Variable time taken to return to the starting position for the next operation.
Fixed time needed for changing gears and adjusting speeds.
The distance over which earth is pushed from the cutting point to the dumping location.
This section discusses the cycle time of bulldozers, including its components and factors affecting productivity.
The section elaborates on defining cycle time in bulldozer operations, including pushing, backtracking, and maneuvering. It highlights how these components impact operational efficiency, emphasizing the importance of haul distance and machine speed in calculating cycle time and productivity.
This section provides a comprehensive analysis of the cycle time of bulldozers, distinguishing between the different components of the cycle time, including fixed and variable times. The key elements that make up the cycle time include:
The cycle time is divided into fixed time (related to maneuvering) and variable time (push and backtrack), where the variable time is particularly dependent on haul distance. The longer the haul distance, the more time it will take for pushing and returning.
The section also outlines how to determine the push time, backtrack time, and maneuver time using performance charts. These charts provide data on how speed varies with total resistance and project conditions, allowing for accurate estimates of productivity.
Furthermore, an estimation of productivity using loose cubic meters per hour is presented, explaining how to calculate it based on the blade load and cycle time. Factors affecting job efficiency, such as terrain conditions and operator skill, are also discussed, emphasizing their importance in estimating overall productivity and costs associated with earthmoving operations.