5.1. Details of the Example Problem

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.

The cycle time for a bulldozer is the total time it takes to perform a full operation which includes cutting, pushing, dumping, and returning. Cycle time is essential to understand bulldozer efficiency, as it outlines how long the machine spends on various tasks. The process is sequential: first, the bulldozer cuts the earth, then pushes it to the desired location, dumps it, and finally backtracks to prepare for another cycle. Hence, each of these steps contributes to the overall cycle time.

Think of a bulldozer like a delivery truck making a round trip. It has to stop at a warehouse to load, drive to the delivery location, drop off the items, and then return to the warehouse. Just as you would measure how long the truck takes for the entire round trip, measuring the bulldozer's time to complete its tasks helps assess its overall effectiveness.

So, other things are maneuvering, maneuvering in the sense whatever adjustments you do, like for increasing the speed, accelerating or decreasing the speed, changing the gear, so the time needed for changing the gear, all those things comes under the maneuvering. 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.

In bulldozer operations, 'maneuvering' refers to the adjustments made by the operator, such as changing gears or speeds, which takes a relatively consistent and predictable amount of time, termed as fixed time. On the other hand, 'push time' and 'backtrack time' are classified as variable time because they can change based on the haul distance—the further the distance, the more time it will take to push and return.

Imagine a runner participating in a race. The time they take to start running (fixed time) is relatively short and consistent. However, the time it takes to complete the race (variable time) will differ based on the distance of the race. Longer races take more time, similar to how bulldozer push time and backtrack time increase with greater haul distances.

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. So, in the earlier lecture, I discussed about how to determine the speed from the performance chart.

To accurately measure push and backtrack times, it’s crucial to know both the distance traveled (haul distance) and the speed of the bulldozer. Speed can be derived from a performance chart that outlines how different conditions affect the bulldozer’s performance. Understanding these factors helps in calculating the time taken for each part of the bulldozer's cycle.

Think of it like planning a road trip. Before setting out, you would first determine the distance to your destination and how fast you plan to drive. This knowledge allows you to estimate how long the journey will take, just as understanding distance and speed helps the operator estimate the bulldozer's operational time.

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. So, in all the machines, there are 2 types of transmission possible.

Maneuver time refers to the amount of time taken to make adjustments such as changing gears, accelerating, or decelerating. This time can vary significantly depending on the type of transmission in the bulldozer. The two common types are direct transmission, where the operator manually changes the gears, and automatic systems, which adjust these settings without manual input.

Consider driving a car: if you have a manual transmission, you have to shift gears yourself, which can take extra time and practice. In contrast, with an automatic transmission, the car shifts gears on its own, making driving smoother and quicker in some situations. Similarly, the transmission type in bulldozers influences how quickly it can respond to the operator’s commands.

So, 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.

To estimate productivity, which is measured in loose cubic meters per hour, it’s important to specify the condition of the material. Loose state means that the material has been excavated and is much easier to handle than when it is in its natural packed form, known as bank state. This distinction is essential to provide accurate estimates of the bulldozer's output.

Imagine filling a bag with sand. If you pack the sand tightly into the bag (bank state), it will look different and weigh more than when you simply scoop loose sand into the bag (loose state). Just like estimating how much sand you can carry, estimating productivity requires knowing the state of the material being moved.

So, for that you need to know unit cost is nothing but cost per loose meter cube. Say I am going to find it in the loosen state cost per meter cube of earth moved, I need to calculate. It is nothing but your hourly cost associated with the machine divided by the hourly productivity.

To find the unit cost of production for earthmoving, you calculate the cost associated with the bulldozer’s operation over an hour and then divide that by the calculated productivity. This gives you the cost per loose cubic meter moved, which is critical for budgeting and bidding in construction projects.

Think of a lemonade stand. If you spend $5 on ingredients and can make 10 glasses of lemonade in an hour, the unit cost per glass would be$5/10 = $0.50. Similarly, knowing how much it costs to operate the bulldozer helps in setting the right prices for the services it provides.

So, after estimating this, you have to take into account the job efficiency. So, one thing you should know that your machine is not going to be operated for the entire 60 minutes in an hour. So, depending upon your project condition, it may operate for 45 minutes or 50 minutes. So, it may even operate only for 30 minutes, it depends upon your project condition.

Job efficiency is the proportion of time the machine is actually working compared to the total available time in an hour. This efficiency can be influenced by factors such as the project's specific conditions and operational delays. For accurate productivity estimates, it's crucial to take this efficiency into account.

Imagine you have a one-hour study session. If you only focus and work effectively for 30 minutes, your study efficiency is 50%. Recognizing how much time is effectively spent on tasks, much like in our bulldozer example, helps in realistic planning and goal setting.

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