5. Example Problem on Productivity Estimation

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.

Cycle time refers to the total time a bulldozer takes to complete one full operation cycle, which includes cutting the earth, pushing it to a designated spot, dumping it, and then returning to the starting position. Each part of this process contributes to the overall cycle time. The cycle time is critical as it helps estimate how efficiently the bulldozer is operating.

Think of the bulldozer as a chef preparing a meal. The cycle time would be similar to the time it takes from when the chef starts chopping vegetables, cooking them, serving the dish, and then cleaning up before starting the next meal. Just like every step in the cooking process takes time, every step in the bulldozer's operation adds to the total cycle time.

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?

In the context of bulldozer operations, fixed time refers to the time it takes for maneuvers (like changing gears), which is relatively constant. In contrast, variable time refers to the push and backtrack times, which can change based on factors like haul distance and the speed of the bulldozer. The further the distance or the slower the speed, the longer these variable times will be.

Imagine driving a car on a long road trip. The time it takes to shift gears (fixed time) remains relatively the same regardless of distance. However, the time spent driving to your destination varies based on traffic conditions and how far away you are (variable time). Thus, in both cases, you have a predictable part and a part that changes.

To know the push time and the backtrack time, I need to know the travel distance or the dozing distance or the haul distance.

To calculate the push time (the time taken to move the bulldozer forward) and backtrack time (the time taken to return to start position), you first need to know certain distances, specifically the dozing distance or haul distance. The longer the distance, the longer the push and backtrack times will be.

Think of pushing a shopping cart. If your grocery store requires you to push the cart from one end of the store to the other far down aisle, it will take longer than if the distance is just a few feet away. Thus, just as knowing the distance affects your time in the store, it similarly affects the bulldozer's operation.

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.

The speed of the bulldozer can be determined from a performance chart, which presents data on speed versus total resistance. This chart helps operators find the optimal speed based on the specific project conditions and terrain. Knowledge of the speed is crucial as it directly impacts the cycle time and productivity.

Imagine running a race; knowing your average speed can help you understand how long it will take you to finish the race. Similarly, by using the performance chart, operators can estimate how quickly they can complete their work, akin to planning your strategy to finish the race effectively.

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.

Maneuver time involves the adjustments made while operating the bulldozer, like changing gears or modulating speed. This time can vary significantly depending on whether the bulldozer uses direct transmission (manual gear changes) or automatic options like torque converters. The less time spent on these adjustments, the more efficient the operation.

Consider a cyclist who has to change gears frequently while riding up and down hills. If the cyclist has an automatic gear system that adjusts seamlessly, they can focus on pedaling faster rather than shifting gears, much like how bulldozers with automatic systems can operate more efficiently.

Now let us see how to estimate the productivity of the bulldozer. So, we are going to estimate the productivity a lose meter cube per hour.

Productivity of a bulldozer is calculated in terms of loose cubic meters moved per hour. This is obtained by dividing the blade load (amount of material the bulldozer can move in one cycle) by the total cycle time, which includes all components of time discussed earlier. It is crucial to specify whether the volume is measured in a loose state or bank state to avoid confusion.

Imagine a construction worker moving sand with a wheelbarrow. If they need to know how much sand they can transport in an hour, they would assess how much fits in the wheelbarrow (blade load) and how often they can make trips (cycle time). Similarly, measuring bulldozer productivity relies on these simple principles.

Now, to calculate the unit cost associated with every activity, unit cost of earthmoving operation. So, for that you need to know unit cost is nothing but cost per loose meter cube.

The unit cost of production is calculated by dividing the total cost of operating the bulldozer (including ownership and operational costs) by the productivity measured in loose cubic meters. This calculation is vital for budgeting and for determining bids during contracting work.

This is similar to calculating the cost of producing a specific product in a factory. If a factory has to calculate how much each product costs to produce, they would take their total production costs and divide it by the number of products made, just like how we calculate unit costs for bulldozer operations.

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