Calculation of Total Rolling Resistance - 1.2 | Overview 72 | Construction Engineering & Management - Vol 1
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Understanding Vehicle Weight and Rolling Resistance

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0:00
Teacher
Teacher

Today, we will start with understanding how we convert vehicle weight into tons, crucial for calculating rolling resistance. Can anyone tell me how many kilograms are in a ton?

Student 1
Student 1

Is it 1,000 kilograms?

Teacher
Teacher

That's correct! Now, if our machine weighs 50,000 kg, how many tons would that be?

Student 2
Student 2

It would be 50 tons since you divide 50,000 by 1,000!

Teacher
Teacher

Exactly! Now, if we know the rolling resistance is 28 kg per ton, how would we compute the total rolling resistance for our vehicle?

Student 3
Student 3

I think we multiply the 50 tons by 28 kg per ton.

Teacher
Teacher

Correct! This results in a rolling resistance of 1,400 kg. Great teamwork! Remember: Weight in tons multiplied by rolling resistance gives us total rolling resistance.

Calculating Penetration Resistance

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Teacher
Teacher

Next, let’s discuss penetration resistance. If the tire sinks 6 centimeters into a surface, how do we calculate that resistance?

Student 4
Student 4

We multiply the depth by the effort required, which is 6 kg per ton per centimeter?

Teacher
Teacher

Exactly! So if our machine weighs 50 tons, what do we get for penetration resistance?

Student 1
Student 1

It would be 6 kg multiplied by 50 tons multiplied by 6 centimeters, totaling 1,800 kg.

Teacher
Teacher

That's correct! Good job! So, what is the significance of knowing penetration resistance?

Student 2
Student 2

It helps us understand how much effort is needed to move the vehicle.

Teacher
Teacher

Excellent! That's the connection we were looking for. Always remember how depth impacts resistance!

Total Resistance Calculation

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Teacher
Teacher

Now we’re going to combine what we've learned. How do we find the total resistance the vehicle faces?

Student 3
Student 3

We add the rolling resistance and penetration resistance together!

Teacher
Teacher

Correct! So if we have rolling resistance of 1,400 kg and penetration resistance of 1,800 kg, what’s our total?

Student 4
Student 4

That would be 3,200 kg!

Teacher
Teacher

Well done! Remember, understanding the total resistance helps us determine how much tractive effort we need for the vehicle to operate successfully. Can anyone tell me the required tractive effort we deduce from this?

Student 1
Student 1

It would be the total resistance of 3,200 kg!

Teacher
Teacher

Exactly! Great job summarizing today's lesson.

Introduction & Overview

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Quick Overview

This section covers the calculation of total rolling resistance, factoring in vehicle weight and penetration resistance.

Standard

In this section, we explore how to convert vehicle weight into tons, calculate rolling resistance, determine penetration resistance based on tire penetration, and compute the total resistance faced by a vehicle during operation.

Detailed

In this section, we begin by converting the vehicle weight from kilograms to tons for adequate rolling resistance formulation. The gross weight of the machine is given as 50,000 kg (converted to 50 tons), with the rolling resistance provided as 28 kg per ton. By multiplying the gross weight by the rolling resistance, we calculate a total rolling resistance of 1,400 kg. Additionally, we explore penetration resistance based on the tire's depth of penetration into the surface (6 cm), with the required effort being 6 kg per ton per centimeter of penetration. This results in a penetration resistance of 1,800 kg. Finally, to find the total resistance faced by the vehicle, we add the rolling resistance and penetration resistance, yielding a total of 3,200 kg. This total is critical for determining the necessary tractive effort for the vehicle to operate efficiently under the specified conditions.

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Converting Vehicle Weight to Tons

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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.

Detailed Explanation

In this chunk, we are focusing on converting the weight of a vehicle from kilograms to tons. The reason for this conversion is that rolling resistance is generally calculated in kilograms per ton. Since the vehicle's gross weight is given as 50,000 kg, we can convert this into tons by dividing it by 1000 (since 1 ton equals 1000 kg). Thus, 50,000 kg divided by 1000 equals 50 tons.

Examples & Analogies

Think of it like converting your weight from pounds to stones for a weigh-in contest; it’s the same quantity expressed in a different unit. Just like 200 pounds can be converted to approximately 14 stones, here we convert vehicle weight for easier calculations in engineering.

Calculating Rolling Resistance

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Now the rolling resistance you need to calculate for this particular haul route it 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. So, now we are going to calculate for your particular vehicle what is the total rolling resistance? That is nothing but 1400 kg, so 1400 kg is your rolling resistance.

Detailed Explanation

In this chunk, we are calculating the total rolling resistance using the value of rolling resistance per ton. With the previously calculated gross weight of 50 tons and a rolling resistance value of 28 kg per ton, we multiply these two values together: 50 tons multiplied by 28 kg/ton equals 1400 kg. Therefore, the total rolling resistance the vehicle needs to overcome is 1400 kg.

Examples & Analogies

You can imagine this scenario similar to how much force you need to keep pushing a heavy cart on a flat surface. If the cart weighs 50 units and it requires 28 units of force for every unit of weight to keep it moving, your total required force will increase proportionately as you add weight.

Calculating Penetration Resistance

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Now we need to find the penetration resistance. It is given to you in the problem that the tyre is sinking to the depth of 6 centimeters into the surface. So, you know that for each centimeter of penetration the amount of effort needed is 6 kg per ton per centimeter. So, you multiply that by how much is the depth of penetration? It is nothing but 6 centimeter, and what is the gross weight of the machine? It is nothing but 50 tons. So, that gives you the penetration resistance as 1800 kg.

Detailed Explanation

Here, we are determining the penetration resistance, which is the force required when the tire sinks into the ground. The problem states that each centimeter of penetration requires an additional 6 kg of force per ton of vehicle weight. The tire has penetrated 6 centimeters into the ground, so we multiply the penetration depth (6 cm) with the force required per ton (6 kg/ton) and the gross weight of the machine (50 tons), resulting in a total penetration resistance of 1800 kg.

Examples & Analogies

Imagine if you’re trying to push a heavy object across a deep rug. The deeper the object sinks into the rug, the more effort you’ll need to exert to move it. The depth of the tire in the soil acts just like the depth of the object in the rug, requiring more force the deeper it sinks.

Finding Total Resistance

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Now we can find the total resistance, that is nothing but add your rolling resistance and the penetration resistance. It is nothing but your 1400 kg + 1800 kg, so that gives me the answer as 3200 kg is the total resistance.

Detailed Explanation

In this section, we are calculating the total resistance the vehicle must overcome while moving. The total resistance is the sum of the rolling resistance (1400 kg) and the penetration resistance (1800 kg). Adding these two values gives a total resistance of 3200 kg that the vehicle needs to counteract to move effectively.

Examples & Analogies

Think of it like carrying heavy boxes while walking: if one box (the rolling resistance) weighs 1400 kg and another box (the penetration resistance) weighs 1800 kg, the combined total weight you will need to carry is 3200 kg. This is what the vehicle has to overcome to keep moving.

Determining Tractive Effort

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So, I need tractive effort of at least 3200 kg to overcome this resistance in a project site. So, the total tractive effort needed to overcome this resistance is 3200 kg. So, select the machine accordingly, that is the purpose of estimating all this resistance, so that we can know what is the required power for your machine? Select a machine that can generate enough power to overcome this resistance.

Detailed Explanation

In this part, we summarize our findings by stating that the vehicle must produce a tractive effort of at least 3200 kg to move against the total resistance calculated earlier. This information is crucial for choosing a machine that can generate sufficient power to manage the identified resistance forces in real-world conditions.

Examples & Analogies

Imagine selecting a backpack to carry your boxes. If you know that you have to carry a total weight of 3200 kg, you wouldn’t select a small backpack; you’d opt for something robust and durable that can comfortably handle the load without breaking, thus ensuring you can complete your task.

Definitions & Key Concepts

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Key Concepts

  • Vehicle Weight Conversion: Converting kg to tons for rolling resistance calculations.

  • Rolling Resistance: The resistance exerted by tires during movement.

  • Penetration Resistance: Resistance encountered due to tire sinking into the surface.

  • Total Resistance: Combined resistance that impacts vehicle efficiency.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • If a vehicle weighs 50 tons with a rolling resistance of 28 kg per ton, the total rolling resistance would be calculated as 50 tons * 28 kg/ton = 1,400 kg.

  • For a tire sinking 6 cm into the ground with a gross weight of 50 tons, the penetration resistance would be 6 cm * 6 kg/ton/cm * 50 tons = 1,800 kg.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Rolling home, heavy as stone, weight in tons not alone, together we roll with force to control.

📖 Fascinating Stories

  • Imagine a heavy truck trying to make its way through soft soil. As it rolls, it struggles, sinking more and needing to push harder. This battle symbolizes how rolling and penetration resistances work together in the world of machinery.

🧠 Other Memory Gems

  • For finding resistance: Remember RP (Rolling Penetration) Correctly; use Weight * kg/ton.

🎯 Super Acronyms

RTP (Rolling - Tractive - Penetration) - elements to calculate total resistance!

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Rolling Resistance

    Definition:

    The resistance faced by a rolling object due to deformation of the tires and the surface.

  • Term: Penetration Resistance

    Definition:

    Resistance encountered when a tire sinks into the surface, measured in relation to the weight of the vehicle.

  • Term: Tractive Effort

    Definition:

    The force required to overcome resistance forces and move a vehicle.