5.2. Cycle Time for Scraper and Pusher

So, now let us work on the first problem on productivity estimation of the scraper. So, a scraper with the assistance of the pusher is moving the dry earth soil having unit weight of 1660 kg per bank meter cube.

In this section, we are focusing on how to estimate the productivity of a scraper and its accompanying equipment, the pusher. A scraper carries dry earth soil, which has a specific unit weight. Understanding the unit weight is crucial for calculating how much material the scraper can effectively transport. The cycle time for both the scraper and the pusher determines the overall efficiency of the earth-moving operation. The goal is to balance the work done by both machines to improve productivity.

Think about it like a team of two workers moving boxes. One worker (the scraper) carries a load of boxes, while the other worker (the pusher) helps load boxes onto the first worker. If the first worker takes too long to load, the second worker has to wait, which means the team isn't working efficiently. By figuring out how long each task takes, we can make sure both workers are busy and moving quickly.

So, hope you remember what is swell factor? We have defined what is swell factor in early lecture, it is a ratio of loose dry unit weight of the material by bank dry unit weight of the material.

The swell factor is a crucial concept in earth moving and excavation. It helps us understand how much volume of material will change when it's moved from one state to another. The ratio is defined as the loose dry unit weight divided by the bank dry unit weight. When pushing soil, the additional pressure from the pusher increases the density of the material (hence increasing the swell factor) due to compaction, which is essential for calculating how much can be moved effectively.

Imagine a sponge filled with water. When you squeeze it (like the pusher), the sponge becomes denser, and more water can be pushed out in a small space. Similarly, when the pusher adds pressure, the soil becomes denser and the amount that can be effectively moved changes.

So, the gross weight of the machine is nothing but your empty weight plus the weight of the load in the machine.

To accurately calculate how much load can be transported, we need to determine the gross weight of the scraper when it's loaded. This involves adding the empty weight of the scraper to the weight of the load it carries. Understanding the gross weight helps us ensure that we are not exceeding the machine's safe operating limits, which is critical for safety and longevity of the equipment.

This is similar to weighing yourself before and after carrying a heavy backpack. The increase in weight gives you a clear idea of how much you are carrying. In the same way, knowing the empty weight and the load allows us to ensure the vehicle can handle the total weight safely.

Now, we need to find the total resistance.

Total resistance analysis is critical in estimating how much effort the scraper and pusher need to move the load. There are various types of resistance, such as rolling resistance due to the surface and grade resistance depending on the slope of the haul route. Each segment of the haul route has different resistances based on the slope, which needs to be calculated to understand the actual work required by the scraper and pusher.

Picture riding a bike uphill versus downhill. Going uphill (resistance) is harder and requires more effort, while going downhill makes it easier. Just like the resistance helps determine how fast and efficiently you can pedal, it helps us understand how efficiently the scraper can move materials.

Now, you can calculate the travel time. So, time is nothing but your distance by speed.

Travel time is essential in understanding how long it takes for the scraper and pusher to complete their cycle. By dividing the distance by the speed, we can estimate how long each segment of the haul route will take. This information allows us to sum the time for the entire journey, helping us to identify any inefficiencies in the operation.

Think of it like driving a car. The distance to your destination is like the haul route, and your speed is how fast you're driving. If you want to know how long the trip will take, you divide the distance by your speed. This calculation helps you plan your time, just like travel time helps plan and improve efficiency in using the scraper.

If I go for 5 scrapers what will be the associated productivity and production cost?

Total cycle time combines all elements of operation (travel time, loading time, unloading time) into a single figure that reflects how long it takes to complete one full cycle of work. This is crucial in determining the productivity of the scrapers and pushers in terms of how much material is moved and how costs are affected based on their efficiency.

Imagine preparing a meal where you have various tasks: chopping, cooking, and serving. Each task takes time, and you want to know how long your meal preparation will take in total. Understanding total cycle time in this context helps to break down each task and identify how to make the overall process smoother and more efficient.

So, now the balanced number is 5.68.

Balancing the number of scrapers and pushers is essential for maximizing productivity. It’s calculated by dividing the scraper cycle time by the pusher cycle time to determine how many scrapers can effectively work with one pusher. This balance is crucial to ensure that neither machine has excessive waiting time, maintaining a steady workflow and maximizing productivity.

This is like organizing a relay race where each runner needs to maximize their speed to ensure the next runner is ready without delay. If runners are perfectly timed, the team can finish faster, just like balancing scrapers and pushers keeps the operation running efficiently.

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