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Today, we’re going to learn about converting vehicle weight into tons. Can anyone tell me why we use tons instead of kilograms?
Maybe because tons are easier to work with for larger weights?
Exactly! One ton equals 1000 kilograms. So if our machine weighs 50,000 kg, how many tons is that?
That would be 50 tons!
Great job! Now, let’s remember that when we express rolling resistance, we use kg per ton. Can anyone repeat that?
We express rolling resistance in kg per ton!
Perfect! Now let’s move on to how we calculate rolling resistance.
Now, given our weight of 50 tons and a rolling resistance of 28 kg per ton, how do we calculate the total rolling resistance?
We multiply 50 tons by 28 kg per ton!
Correct! What do we get?
That would be 1400 kg.
Exactly! And that is the rolling resistance the machine has to overcome. Does everyone understand how rolling resistance works?
Yes, it’s based on the weight and the resistance value!
Great! Let’s move on to penetration resistance.
Now let’s look at penetration resistance. If our tire sinks 6 cm into the surface, and we know it takes 6 kg per ton per cm, how can we calculate the total penetration resistance?
We multiply the depth by the resistance value and the gross weight!
Exactly! What’s the formula?
It’s 6 cm × 6 kg per ton per cm × 50 tons.
That’s right! What do we get?
1800 kg!
Great! So, now how do we find total resistance we encounter?
We add rolling resistance and penetration resistance!
Fantastic! That’s a total of 3200 kg. Well done!
Next, we need to consider grade resistance. Can anyone explain what happens when our machine is climbing a slope?
The machine has to work harder against gravity!
Exactly! So, if the slope increases, what can we say about the required tractive effort?
It increases too!
Right! How can we determine the grade resistance? Does anyone remember the guideline?
For every 1% of grade, we need 10 kg per ton.
Exactly! And how about grade assistance?
That’s when we’re going downhill, and it helps reduce the power needed!
Correct! Choosing the right haul route can minimize these resistances significantly.
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The section details how to convert vehicle weight from kilograms to tons, calculate rolling and penetration resistance, and understand grade resistance affecting machinery on various slopes, emphasizing the importance of these calculations in estimating the total power required for effective machinery performance.
The section begins by converting the gross weight of a vehicle from kilograms to tons, a common practice since rolling resistance is expressed in kg per ton. For instance, a vehicle with a gross weight of 50,000 kg is converted to 50 tons. With this conversion, the section explores how to calculate the rolling resistance, which is given as 28 kg per ton. By multiplying the vehicle's gross weight by the rolling resistance value, we find the total rolling resistance to be 1400 kg.
Next, the section covers penetration resistance, calculated based on the depth a tire sinks into the surface—6 cm in this case. Using a value of 6 kg per ton per centimeter, the penetration resistance is found to be 1800 kg. By summing the rolling resistance and penetration resistance, the total resistance against which machinery must exert effort is established at 3200 kg.
Additionally, the section introduces grade resistance, which arises when machinery moves uphill, requiring additional power to overcome gravity's opposition. As the slope percentage increases, so does the required tractive effort, which complicates the selection of an optimal haul route. Conversely, the concept of grade assistance is explained whereby machinery experiences reduced power requirements when moving down slopes.
Lastly, practical calculations are introduced, including the grading guidelines (10 kg per ton for a 1% slope), which can be referenced against available literature. The section closes by discussing the significance of understanding available power, as prescribed by the manufacturer, and the factors affecting usability of that power in real-world conditions.
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So, let us convert the vehicle weight into tons, because your rolling resistance is commonly expressed as kg per ton. So, let us convert the weight of the machine into tons. You know that the gross weight of the machine is given as 50,000 kg. So, 1000 kg = 1 ton, so divided you will get the gross weight of the machine as 50 tons.
In this step, we convert the weight of the vehicle from kilograms to tons to standardize the measurement for rolling resistance calculations. The gross weight of the machine is given as 50,000 kg. Since 1 ton equals 1000 kg, we divide 50,000 kg by 1000 to find the vehicle's weight in tons, resulting in 50 tons.
Think of converting weights similar to how you might convert currency. Just like you can convert dollars to euros based on the current exchange rate, converting kilograms to tons makes it easier to work with standard units in certain calculations.
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Now the rolling resistance you need to calculate for this particular haul route is given as 28 kg per ton. So, you multiply the gross weight of the machine by the rolling resistance value. So, gross weight is 50 tons multiplied by the rolling resistance is 28 kg per ton for that particular haul route. This gives you the rolling resistance of 1400 kg.
Once we have the vehicle weight in tons, we can calculate the rolling resistance. The problem states that the rolling resistance is 28 kg per ton. We perform the calculation by multiplying the gross weight (50 tons) by the rolling resistance (28 kg/ton). Thus, 50 tons × 28 kg/ton = 1400 kg. This means the force opposing the vehicle's motion on the haul route due to rolling resistance is 1400 kg.
Imagine riding a bicycle. If you know how much weight you are carrying per kilometer and how much it slows you down, you can calculate how difficult it will be to pedal based on the weight, just like we calculated rolling resistance based on vehicle weight and resistance per ton.
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Now we need to find the penetration resistance. It is given to you that the tyre is sinking to a depth of 6 centimeters into the surface. For each centimeter of penetration, the amount of effort needed is 6 kg per ton per centimeter. So, you multiply that by the depth of penetration (6 cm) and the gross weight of the machine (50 tons). This gives you the penetration resistance as 1800 kg.
In this step, we calculate the penetration resistance, which is the force needed to push the tyre down into the ground. The problem states that the tyre sinks 6 cm into the surface and requires 6 kg of effort per ton for each centimeter of sinking. We multiply the depth of penetration (6 cm) by the gross weight of the machine (50 tons) and the effort needed per ton (6 kg), resulting in Penetration Resistance = 6 cm × 50 tons × 6 kg per ton = 1800 kg.
Consider trying to push a toy car into the sand. The deeper you try to push it, the harder it gets because the sand resists the car's movement. Just like that, when a vehicle's tyre sinks into soft ground, it faces resistance that we can calculate by considering how deep it sinks.
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Now we can find the total resistance, which is the sum of rolling resistance and penetration resistance. This leads to 1400 kg (rolling) + 1800 kg (penetration) = 3200 kg total resistance. Thus, the tractive effort of at least 3200 kg is needed to overcome this total resistance.
To find out how much total force (resistance) the vehicle must overcome to move, we add the rolling resistance (1400 kg) and the penetration resistance (1800 kg). The calculation gives us a total resistance of 3200 kg. This means that the vehicle needs to generate at least 3200 kg of tractive effort to effectively move along the haul route.
Think of a tug-of-war where both teams need to overcome the combined weight of the opposing team to win. Similarly, in this scenario, the vehicle's engine must produce enough force to overcome both rolling and penetration resistances combined to move forward.
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So, select the machine accordingly, that is the purpose of estimating all this resistance, so we can know what is the required power for your machine. Select a machine that can generate enough power to overcome this resistance.
The aim of calculating the rolling and penetration resistance is to determine the appropriate machinery for the job. Estimating the resistance helps us understand how much power the machine needs to perform efficiently in a given haul route. This informs our decision about which machine to select based on its capabilities.
It's similar to choosing a vehicle for a road trip. If you know the distance and what kind of roads you'll be on, you can select a vehicle with enough power and fuel efficiency to handle those conditions, ensuring a smooth journey.
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
Vehicle Weight Conversion: Converting from kg to tons simplifies calculations for resistance.
Rolling Resistance: A value representing the force resisting motion based on weight and surface.
Penetration Resistance: Resistance caused by tire depth in the surface affecting overall performance.
Grade Resistance: Additional power required for uphill movement against gravity.
Grade Assistance: Reduced effort needed when moving downhill due to gravity.
See how the concepts apply in real-world scenarios to understand their practical implications.
A vehicle weighing 50,000 kg is converted to 50 tons for resistance calculations.
A machine on a slope of 5% will require additional power calculated as 5% * 10 kg/ton.
A tire sinking 6 cm into the surface will have 1800 kg of penetration resistance with proper calculations.
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
To convert weight, remember the clue, kg to tons, it's simple to do, divide by a thousand, don’t forget too!
Imagine a heavy truck, lifting its load up a hill. As it climbs, gravity pulls it back, making it push harder—this is grade resistance! Luckily, it rolls down easily, thanks to grade assistance.
RPG for Resistance: R for Rolling, P for Penetration, G for Grade!
Review key concepts with flashcards.
Review the Definitions for terms.
Term: Rolling Resistance
Definition:
The resistance that opposes the motion of a vehicle when it moves over a surface, commonly expressed in kg per ton.
Term: Penetration Resistance
Definition:
The resistance encountered when a vehicle's tires sink into the surface, measured in kg.
Term: Grade Resistance
Definition:
The force opposing the motion of a vehicle when it is moving uphill, dependent on slope percentage.
Term: Grade Assistance
Definition:
The reduction in tractive effort required when a vehicle moves downhill due to gravitational help.