5.4. Estimating Truck Production

But the loading time will be number of bucket loads multiplied by the bucket cycle time.

Another important thing you have to keep in mind is, for any machine whatever may be the mission we have discussed about different types of machines so far. All the machines we are concerned about the safe gravimetric capacity of the machine. For every machine, what is this safe operating load in terms of weight is given by the manufacturer, so that we call it as a gravimetric capacity. So, only that capacity your machine can take because the structural frame of the machine is designed to handle that particular load only. So, we are not supposed to load the machine beyond the gravimetric capacity. So, since the density of material can vary from case to case, it is always advisable to check whether the load weight is within the safe gravimetric capacity.

Loading time is determined by the number of bucket loads multiplied by the time it takes to complete one loading cycle (bucket cycle time). Each machine, including trucks, has a safe operating limit known as gravimetric capacity, defined by the manufacturer. This is the maximum weight that the machine can safely handle without risking structural damage. It is crucial to adhere to this limit, as overloading can lead to mechanical failures.

Think of a truck like a backpack. Just as a backpack has a maximum weight it can carry without breaking, a truck has a maximum weight (gravimetric capacity) it can safely transport. If you overload the backpack, the straps may break or wear out quickly. Similarly, overloading a truck leads to faster wear and tear, increasing repair costs and reducing its lifespan.

Check the load weight against the gravimetric capacity of the truck, how to check that? For that, you need to know what is the unit weight of your material. If you know the density of your material you can multiply by the volumetric load you will get the actual weight of material in the truck, you will get the truck load. That should be within the rated gravimetric capacity of the machine given by the manufacturer.

To ensure that a truck is not overloaded, it is essential to know the density of the material being transported. By calculating the actual weight of the load using the formula (Density × Volumetric Load), you can compare it to the truck’s rated gravimetric capacity. This is an important step in maintaining the health of the machinery and ensuring operations run smoothly.

Imagine you're trying to lift boxes of different weights for a moving job. Just as you would need to know how much each box weighs to avoid overloading yourself, the truck operator must know the load weight to avoid overloading the truck. If a box is heavier than your carrying capacity, you'd risk injury or strain, just like a truck can suffer damage if overloaded.

See many times you can see that people will put these side boards, and in the trucks commonly you can see they put the side boards and try to increase the volume of the truck. If the material which you are going to handle is less dense, in that case, it will not create much problem, you have to check whether the loaded weight in the truck is within the gravimetric capacity. But if the material is going to be denser like wet sand or other denser material, what happens is there are more chances that your machine may be overloaded.

Increasing the volume of a truck's load by adding sideboards can lead to overloading, especially with denser materials. While it may seem like an effective way to boost productivity, it can cause significant problems. If the truck carries materials that are dense, such as wet sand, there is a higher risk of exceeding the truck's gravimetric capacity, leading to mechanical failures and higher operational costs due to increased wear and tear.

Consider a tightrope walker carrying a long pole. If the pole is too heavy, the walker risks losing balance and falling. Similarly, adding denser materials to a truck can exceed its safe operating load, jeopardizing not just the truck but the entire operation. The balance must be maintained between performance and safety.

That means the weight of material in the truck will be above the safe gravimetric capacity defined by the manufacturer. In that case, it will result in a lot of wear and tear to the machine, so particularly your tires will flex and it will result in abusing of tires. So, you know that for most of the machines the tire cost is almost 35% of the truck operating cost.

Operating a truck beyond its gravimetric capacity can cause significant damage, particularly to the tires. Overloaded tires undergo extra stress and wear out much faster, potentially leading to costly repairs and replacements. Since tires represent a substantial portion of truck operating costs, overloading not only impacts safety but also the financial bottom line of the operation.

Think about driving a car with a flat tire versus having a well-inflated one. The flat tire puts extra strain on the car, leading to more wear and tear, just like overloading a truck does on its tires. Regularly maintaining your tires keeps your car safe and efficient, just like adhering to a truck's weight limit keeps it operational and minimizes repair costs.

So next is about the dumping time. So, as we discussed earlier the dumping time will depend upon the type of hauling unit whether it is going to be rear dump or it is going to be bottom dump or side dump accordingly the dump time will vary. Whether the material is easy flowing material or sticky material, rock, blasted rock, all these things will affect your dumping time. And the congestion in the dumping area, you know that in the construction site, many equipment will be working parallel.

Dumping time is influenced by several factors, including the type of dumping mechanism (rear, bottom, or side dump) and the nature of the material being handled. If the materials are sticky or consist of rocks, they will take longer to dump. Moreover, if the dumping area is congested with other machinery, it can cause delays in the dumping process, further affecting efficiency.

Picture a busy restaurant where a server is taking orders. If the restaurant is packed with customers (congestion), it takes longer for the server to get to the table and deliver food. Similarly, if the dumping area is busy with various machines, the dump truck may have to wait, slowing down operations.

Haul time it depends upon your haul distance and the speed, speed you can get it from the performance chart. So, to use the performance chart, you need to know what is the weight of the machine and also you need to know what are all the resistances in your project site.

Haul time is determined primarily by the distance traveled and the speed of the hauling unit. The speed can typically be derived from a performance chart, but this requires knowledge of the truck's weight and any resistances encountered on-site, such as rolling resistance and grade resistance (slope). This data will help in accurate timing and scheduling of operations.

Imagine calculating how long it will take to drive from one city to another. You consider how far it is (haul distance) and how fast your car can go (speed) under various conditions (like traffic), just as you must account for distance and vehicle speed for trucks on a job site.

Now let us see how to balance the interdependent machines, trucks and the excavators. Balancing the capacity of the hauling equipment and the excavator bucket size will result in maximum loading efficiency and reduce total cost.

Balancing the number of trucks with the capacity of excavators is critical for achieving optimal productivity. When the capacity of the trucks aligns closely with the bucket size of the excavator, both can operate efficiently without significant waiting time for either piece of equipment. This balance leads to enhanced productivity and lower costs over the long run.

Think of it like a relay race, where the runner passes the baton to the next runner. If the outgoing runner is too slow or too fast compared to the incoming runner, the race will be inefficient. Similarly, balancing the capabilities of trucks and excavators ensures a smooth transition of materials, optimizing the speed of the operation.

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