2.2. Calculating Blade Load and Cycle Time

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 taken for the bulldozer to complete one full operation cycle. This includes the time to push earth, backtrack to the starting position, and maneuver into the correct position for the next push. Understanding cycle time is crucial for estimating the efficiency and productivity of the bulldozer during earthmoving tasks.

Think of a bulldozer's cycle time like a runner completing a lap. The runner has to run to a point (push the earth), return to the start (backtrack), and then adjust their position to start the next lap (maneuver). The total time for this entire process is similar to the cycle time of the bulldozer.

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. Because it is variable depending upon your haul distance.

In calculating cycle time, we differentiate between fixed time and variable time. Fixed time includes the consistent time requirements for maneuvering the bulldozer. Variable time, however, changes based on the haul distance, which is the distance the bulldozer has to push the dirt. Longer distances mean longer push times and backtrack times.

Imagine a taxi driver who always takes 10 minutes to get the car ready (fixed time) but takes variable time to reach a destination depending on how far away it is. Similarly, the bulldozer has consistent and variable times that affect how quickly it can complete its tasks.

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 push time, we need to know both the distance the bulldozer will push material and the speed at which it will move. The formula for push time typically involves the relationship between speed and distance. The further the dozing distance, the longer the push time will be.

Consider a person pushing a shopping cart down an aisle. The further they have to push the cart, the longer it will take them based on their speed. The same applies to the bulldozer - more distance equals more time spent pushing.

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 understand how fast the bulldozer can push, we refer to a performance chart that provides speeds under various conditions. Knowing the terrain, rolling resistance, and grade resistance allows us to calculate the operating speed of the bulldozer, which is crucial for accurate cycle time and productivity estimations.

Think of a bicycle rider adjusting their speed depending on the slope of the road. If the road is flat, they can go faster, while uphill slows them down. The bulldozer’s speed varies similarly based on the site conditions.

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 is the period required for adjustments in operation, such as changing gears or accelerating. This time can vary greatly depending on whether the bulldozer uses manual gear changes or an automatic system. Understanding this is important for accurate cycle time calculations since different types of transmissions will yield different maneuver times.

Imagine a driver in a manual car versus an automatic. The manual driver takes extra time to shift gears at the right moments, while the automatic system does it quickly and efficiently. Similarly, the bulldozer's maneuver time is influenced by its transmission type.

Depending upon this transmission mode, your maneuver time will change. Say if you are going to go for power shift that is automatic gear change, the maneuver time is 0.05-minute.

The type of transmission directly affects maneuver time. For example, power shift transmissions (automatic) allow for quicker adjustments than manual ones. This difference is quantified in terms of minutes, significantly impacting the overall efficiency and cycle time of operations.

Think of a vending machine. An automatic one quickly delivers a drink with the push of a button, while a manual machine requires more steps to get the same item. The bulldozer operates similarly, with automatic transmissions doing the job faster.

So, after estimating this, you have to take into account the job efficiency.

Job efficiency takes into account that the bulldozer will not operate at full capacity for the entire duration. This means estimating how long the machine can effectively work within an hour. The efficiency ratio must be factored into productivity calculations to provide a realistic output estimation.

Just like a student might not study non-stop for an hour and instead take breaks, the bulldozer won't be working every moment of its hour due to possible delays or inefficiencies.

So, for that you need to know unit cost is nothing but cost per loose meter cube.

Unit cost of production refers to the expenses associated with moving a cubic meter of earth. This requires knowing the a) the hourly cost of operating the bulldozer and b) the productivity during that hour. With both figures, we can determine a cost-effective operation.

Imagine a pizza shop that knows how much it costs to make one pizza and how many pizzas it can make in an hour. By dividing the costs by the output, they can set a price that covers their expenses.

So, what we discussed is one way of estimating the productivity. So, for that you need the information on the blade capacity and you need the information of the haul distance and you need the information on the rolling resistance and grade resistance.

To estimate productivity, one method involves knowing the bulldozer's blade capacity, haul distance, and site conditions like rolling resistance. These factors determine how quickly and efficiently the bulldozer can perform its tasks. Combining these with correction factors will yield the actual productivity rate.

Think of baking cookies. The capacity of your oven, the distance and time you bake, and the ingredients play a role in determining how many cookies you can produce. In the same way, the bulldozer's various performance features and external conditions determine how productive it can be.

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