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A short class with Sarah and her students. The other ways are under More.
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Today, we'll focus on cycle time in bulldozer operations. Can anyone tell me what cycle time entails?
Does it include the time spent on pushing and returning?
Exactly! The cycle time consists of push time, backtrack time, and maneuver time. Push time is the time spent moving material forward, while backtrack time is the return to the starting position.
What affects the push time specifically?
Good question! Push time is dependent on haul distance and the speed of the bulldozer. Let's remember this with the mnemonic 'PUSH' – P for Push time, U for Underhaul distance, S for Speed, and H for Haul distance.
So, if the haul distance increases, then push time also increases?
Correct! The longer the distance, the more time it takes.
What about the maneuver time?
Hold that thought; we’ll discuss that in the next session!
Continuing from where we left off, let's explore fixed and variable times. Who remembers the distinction?
Variable time changes based on factors like haul distance, while fixed time doesn't?
Exactly right! In our cycle time, push and backtrack are variable, but maneuver time can be fixed based on transmission type.
So what types of transmissions are we talking about?
We have direct transmission and automatic systems. With direct, an operator adjusts gears, leading to longer maneuver times.
And automatic makes it faster, right?
Exactly. Automatic systems, like torque converters, cut maneuver time nearly in half. We can remember that with the acronym 'AUTO' – A for Automatic, U for Unimpeded, T for Time-saving, and O for Operation ease.
That sounds very efficient!
It absolutely is. Keeping maneuver time low is crucial for productivity.
Think of speed as the vehicle's 'heartbeat' in relation to productivity.
It helps us find out how fast we can move material, right?
Spot on! You can determine speed from performance charts. What factors influence this?
Total rolling resistance and grade conditions are key!
Exactly! The heavier the resistance, the slower the speed. We can use the acronym 'SPEED' – S for Soil conditions, P for Performance charts, E for Engine output, E for Efficiency, and D for Distance.
Shouldn't we also consider the load of the bulldozer?
Absolutely! The load plays a crucial role in determining efficiency.
In a manual transmission bulldozer, maneuver time is typically around 0.1 minute (6 seconds), while in an automatic transmission, it is reduced to 0.05 minutes (3 seconds).
The speed of a bulldozer can be determined using a performance chart by estimating the total resistance based on site conditions.
Push and return as fast as can, time's key in this earth-moving plan.
Imagine a bulldozer named 'Benny' who always took extra time to change gears; Benny learned that using automatic gears saved him valuable time, helping him push more dirt each day.
To remember cycle time, think 'P-B-M': P for Push, B for Backtrack, M for Maneuver.
MUTE - Maneuver, Underhaul, Time, Efficiency - helps remember cycle time components.
Term
Cycle Time
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Term
Maneuver Time
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Term
Transmission Type
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The total time taken by a bulldozer to complete one full operational cycle, including push, backtrack, and maneuver times.
The time required for the bulldozer to push material over a specified distance.
The time taken to return to the original position after dumping the material.
The time taken to change speeds or gears during the operation.
The mechanism by which the bulldozer's engine power is transferred to the wheels—can be manual or automatic.
A graphical representation that outlines the expected operational speeds based on various resistance conditions.
The section discusses how different types of transmission systems in bulldozers affect cycle time, including factors like push time and maneuver time.
This section outlines the relationship between transmission types (manual vs. automatic) and cycle time for bulldozers. It details how maneuver time varies with different transmission systems and emphasizes the importance of calculating push and backtrack times based on haul distance and speed to accurately estimate bulldozer productivity.
In bulldozer operations, the cycle time is comprised of multiple components including push time, backtrack time, and maneuver time. The section highlights that while push and backtrack times are variable and depend on haul distance and operational speed, maneuver time is influenced by the type of transmission used—manual or automatic.
Manual transmission requires the operator to manually change gears, which leads to longer maneuver times, while automatic systems like torque converters automatically adjust to load conditions, significantly reducing maneuver time. The text establishes that push time is determined by the haul distance and speed achievable under project conditions, which can be derived from performance charts based on total resistance factors. By understanding these dynamics, operators can better estimate the productivity and efficiency of bulldozer operations, crucial for effective project management.