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A short class with Sarah and her students. The other ways are under More.
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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.
Converting from kg to tons simplifies calculations for resistance.
A value representing the force resisting motion based on weight and surface.
Resistance caused by tire depth in the surface affecting overall performance.
Additional power required for uphill movement against gravity.
Reduced effort needed when moving downhill due to gravity.
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!
Remember RAVE: R = Rolling Resistance, A = Assistance, V = Vehicle Weight, E = Effort, to cover the key resistance topics!
Term
What is rolling resistance?
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Term
What is penetration resistance?
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Term
How does a slope affect grade resistance?
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Term
Define grade assistance.
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The resistance that opposes the motion of a vehicle when it moves over a surface, commonly expressed in kg per ton.
The resistance encountered when a vehicle's tires sink into the surface, measured in kg.
The force opposing the motion of a vehicle when it is moving uphill, dependent on slope percentage.
The reduction in tractive effort required when a vehicle moves downhill due to gravitational help.
This section discusses the conversion of vehicle weight into tons, the calculation of rolling resistance, and the factors affecting tractive efforts needed for project site operations.
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.