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Interactive Audio Lesson
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Converting Vehicle Weight and Calculating Resistance
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To start, let’s convert vehicle weight into tons since rolling resistance is frequently expressed in kg per ton. Can anyone tell me how we do that?
We divide the weight in kg by 1000, because 1000 kg equals 1 ton.
Exactly! For example, if our machine weighs 50,000 kg, how many tons does it weigh?
That would be 50 tons.
Correct! Now, the rolling resistance is given as 28 kg per ton. Can anyone help me calculate the total rolling resistance for our 50 tons machine?
We multiply 50 tons by 28 kg per ton to get 1400 kg.
Great job! So the total rolling resistance is 1400 kg.
What does that mean for the machine? How do we move it?
It means that the machine needs 1400 kg of tractive effort to overcome that resistance!
Understanding Penetration and Total Resistance
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Now let’s add another layer—penetration resistance. If the tire sinks 6 cm into the surface, how do we figure out the penetration resistance?
We multiply the depth of penetration by the effort required per centimeter and then by the total weight.
Very well! Given that it requires 6 kg per ton per centimeter for penetration, how do we calculate that?
We can multiply 6 kg by 6 cm and then by 50 tons, resulting in 1800 kg.
Exactly! Let’s find the total resistance. Can someone add the rolling and penetration resistance for us?
That would be 1400 kg plus 1800 kg, equaling 3200 kg total resistance.
Correct! Now, we know the machine needs at least 3200 kg of tractive effort to overcome this resistance.
Exploring Grade Resistance and Assistance
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When machinery ascends a slope, what do we call the opposing force?
That’s called grade resistance!
Exactly! And what happens when the machine is moving down a slope?
That’s grade assistance, which reduces the power needed!
Perfect! Let’s say we have a 5% slope. How would we quantify the grade resistance required?
For each 1% of grade, we need 10 kg per ton. So it would be 5 times that for a 5% slope, or 50 kg per ton.
Right! Can someone calculate the needed tractive effort if our machine is 50 tons?
That would be 50 times 50 kg, which equals 2500 kg!
Awesome! So, how do we apply this when planning our haul route?
We should avoid steep slopes if we can, to reduce required power and costs.
Introduction & Overview
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Quick Overview
Standard
The section explains how to convert vehicle weight into tons for calculating rolling resistance, penetration resistance, and total resistance. It then explores the concepts of grade resistance and grade assistance, providing guidelines for determining the required tractive effort for machines working on slopes. Additionally, it elaborates on the usable power from machines, emphasizing the importance of traactile resistance and the influences of project conditions on power generation.
Detailed
Detailed Summary of Rimpull and Drawbar Pull
This section centers on understanding the dynamics of rimpull and drawbar pull in relation to machinery performance on varying terrains. It begins with conversions of vehicle weight from kilograms to tons, essential for calculating resistance values used in heavy machinery. The rolling resistance is defined as the force opposing motion due to the weight of the vehicle, which in the example provided, totals at 1400 kg when a gross weight of 50 tons and a rolling resistance of 28 kg per ton are applied.
Further, the section delves into penetration resistance, characterized by tires sinking into a surface. Calculating performance requires understanding how penetration into the surface increases the required tractive effort due to resistance (
1800 kg for a 6 cm penetration into the surface). The overall resistance encountered by the machine is quantified by summing rolling and penetration resistances, leading to a total resistance of 3200 kg.
The teacher then introduces grade resistance, a crucial factor when machines ascend slopes, requiring additional effort due to gravity. The grade assistance concept is also presented, which reduces the necessary power when descending slopes. A clear guideline is given: for a slope of 1% grade, an estimated 10 kg per ton of tractive effort is required, applicable mainly for slopes under 10%.
The section emphasizes the significance of selecting haul routes effectively to minimize resistance and elevate power generation efficiency for machinery. Finally, the available power rating from manufacturers is discussed, highlighting factors such as operational conditions affecting real-world power generation. It is concluded that usable power must emerge post-calculating resistance efforts, with rimpull for wheeled machinery and drawbar pull for tracked machinery defining how much force is effectively exerted at the ground contact point.
Audio Book
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Understanding Rolling Resistance
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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. Now the rolling resistance you need to calculate for this particular haul route it is given as 28 kg per ton.
Detailed Explanation
This chunk introduces the concept of rolling resistance, which is the force resisting motion when a vehicle rolls on a surface. First, the gross weight of a machine, given in kilograms (50,000 kg), is converted into tons (50 tons). This conversion is necessary because rolling resistance is typically expressed in kg per ton. For this machine, the rolling resistance specified for the haul route is 28 kg per ton, meaning for each ton of weight, an additional force of 28 kg is required to move the vehicle.
Examples & Analogies
Think of rolling resistance like trying to push a heavy shopping cart on a bumpy surface versus a smooth one. The bumps create resistance (like rolling resistance), making it harder to push. If your cart is heavy (like a truck), every additional kilo of weight means you need more effort (force) to push it.
Calculating Total Rolling Resistance
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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 section, we see how to calculate total rolling resistance using a formula. You multiply the gross weight of the vehicle (50 tons) by the rolling resistance (28 kg per ton) to get the total rolling resistance, which equals 1400 kg. This value tells you the total extra effort needed to move the vehicle solely due to the weight and the specified rolling resistance.
Examples & Analogies
Imagine pushing a sled that weighs 50 kg across snow. If the snow creates a drag (rolling resistance) of 28 kg for every 100 kg, you would need to exert an extra 1400 kg of force to just get it moving. It’s like the heavier the item, the harder it becomes to push across a rough surface.
Penetration Resistance Calculation
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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.
Detailed Explanation
Penetration resistance refers to the resistance encountered when a tire sinks into a surface, such as mud or soft soil. In our case, the tire sinks 6 cm into the surface. The resistance is determined by knowing that each centimeter of penetration requires an additional force of 6 kg per ton. Therefore, we multiply the depth of penetration (6 cm) by 6 kg per ton and then by the gross weight of the vehicle (50 tons) to get the total penetration resistance.
Examples & Analogies
Consider a car tire sinking into soft sand at the beach. As the tire sinks deeper, it requires more effort to pull it out. If you're on sandy ground, every inch of sink means you have to push harder (more penetration resistance). Here, each cm of tire penetration adds extra force needed to keep driving.
Total Resistance Calculation
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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
To find the total resistance a vehicle faces, we simply add the rolling resistance (1400 kg) to the penetration resistance (1800 kg). This results in a total of 3200 kg, representing the total effort required to overcome both types of resistance when moving the vehicle across the specified haul route.
Examples & Analogies
Think of this total resistance like trying to walk on two different terrains - one is rocky (like rolling resistance) and the other is muddy (like penetration resistance). The total effort you need to exert to walk through both terrains is the sum of the effort needed for each terrain.
Understanding 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
The term 'tractive effort' refers to the force required to move a vehicle and overcome the total resistance (3200 kg). This calculation is essential for selecting the right machine; it must be powerful enough to produce at least this level of tractive effort in order to function effectively on the project site.
Examples & Analogies
Think of a car trying to drive up a steep hill. To ensure it can make it up, you need to know how much power (tractive effort) the car must have capable of overcoming gravity and resistance, just like knowing how much horse power you need when trying to tow a trailer up a hill.
Grade Resistance Explained
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Now so far, we have discussed about the rolling resistance, let us look into the other part of the resistance in your project site that is your grade resistance. Most often you can see that equipment has to climb up a slope. So, when the machine is climbing up the slope, obviously you need some additional efforts to make it move up the slope because it is pulling against the gravity.
Detailed Explanation
Grade resistance is the additional effort needed when a vehicle is moving up a slope. This is because the vehicle has to work against the force of gravity. The steeper the slope, the more tractive effort is required to move the vehicle forward. It’s important to consider this when planning any transport on hilly terrain.
Examples & Analogies
Imagine trying to ride a bicycle uphill. You feel the extra effort required to push yourself up the slope, compared to riding on a flat road. That extra effort required to go uphill is similar to grade resistance, which makes your ride harder and requires more power.
Understanding Grade Assistance
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So, similar to this, we should also know about what is grade assistance? So, we discussed about what is grade resistance, there is something called as grade assistance that means what? When your machine is moving down the slope, you can see that the amount of power needed gets reduced because it can easily move down by the gravity.
Detailed Explanation
Grade assistance refers to the reduction in the amount of power needed when a machine moves down a slope instead of up. The gravitational pull helps to push the vehicle down, thereby requiring less tractive force compared to moving uphill. This can greatly lower fuel consumption and preserve power.
Examples & Analogies
Riding your bike downhill feels much easier than going uphill, right? Just like how gravity helps you glide down, machines benefit from grade assistance when descending slopes, requiring less effort and, hence, less power.
Calculating Grade Resistance
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So, grade resistance is nothing but by simple elementary I mean a mechanics people have worked out this the relations. Say for example, for 1% of grade so the amount of tractive effort needed to overcome this 1% of grade it is 10 kg per ton.
Detailed Explanation
To calculate grade resistance, a guideline is given that for every 1% increase in slope, an additional effort of 10 kg is required for each ton of weight. This rule helps in estimating the total effort needed based on the gradient of the slope. The steeper the slope, the greater the resistance that must be overcome.
Examples & Analogies
Consider hiking up a hill: the incline makes you exert more energy. If we use percentages to measure steepness, it's like saying for every 1% of incline, you need to push harder. So for a 5% incline, you'd need to exert a cumulative effort that reflects this increased push against gravity.
Equivalent Gradient for Rolling Resistance
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So, you can convert a rolling resistance also into equivalent gradient. The rolling resistance which you have expressed in kg per ton, that you can converted into gradient percentage equivalent gradient.
Detailed Explanation
Rolling resistance can be expressed as an equivalent gradient, making it easier to compare with grade resistance. By knowing that 1% grade equals 10 kg per ton, rolling resistance expressed in kg per ton can be converted into a percentage. This allows for clearer understanding alongside grade resistance, facilitating better calculations.
Examples & Analogies
Think of solving problems with multiple unknowns. Converting rolling resistance into gradient makes it simpler, just like converting all your measurements into the same unit, ensuring easier comparisons and calculations when planning your project.
Usable Power in a Project Condition
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Now we are going to look into the estimation of the available power.
Detailed Explanation
The available power of a machine is determined by the manufacturer and can be rated for standard conditions. However, in practical scenarios, conditions such as altitude and temperature can impact the machine's performance, which means that the actual usable power could be less than what is rated. Understanding this distinction is important in order to choose the right machine for the job.
Examples & Analogies
Imagine a sports car capable of going 0-60 miles per hour in a flat area. Now, take it to a mountain: its performance won't be the same because of altitude and other environmental factors that slow it down. Similarly, knowing how much usable power you truly have in your working environment is crucial.
Estimating Usable Power
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So, now let us see what is the usable power? So, out of the available power prescribed by the manufacturer, how much amount of power becomes usable to you?
Detailed Explanation
Usable power refers to the portion of a machine's power that can be utilized after accounting for the resistance encountered onsite. To find the usable power, you take the total power and subtract the power used to overcome resistance. This usable power is vital for carrying out tasks like towing or hauling material effectively.
Examples & Analogies
Picture a delivery truck that has a certain horsepower rating. But when it is loaded heavily with packages and struggles to move, the effective power it can apply to drive is less than its rated horsepower. Thus, knowing the usable power is essential for the truck to effectively complete its deliveries.
Rimpull and Drawbar Pull Defined
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The usable power you can express in terms of rimpull or drawbar pull. So, depending upon the mounting of your machine. So, if it is going to be wheel or tyre mounted machine, we call it as rimpull. The usable tractive force developed at the point of contact between the tyre and the ground is called as a rimpull.
Detailed Explanation
Rimpull (for wheeled machines) and drawbar pull (for tracked machines) are terms used to describe the usable force available at the point of contact with the ground. Rimpull refers to the force generated at the tires, while drawbar pull refers to the force available to move a load through a hitch or drawbar for tracked machines. Both concepts capture the effectiveness of the machine in terms of power transfer to the surface below.
Examples & Analogies
Think of a bulldozer pushing dirt. The strength it pushes with through its tracks represents the drawbar pull. Meanwhile, a pickup truck pulling a trailer's weight through its rear wheels shows rimpull. Both are necessary to understand how well these vehicles can perform their tasks on the job site.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Rimpull: Effective tractive force on wheels; important for calculating propulsion.
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Drawbar Pull: Equivalent force for tracked vehicles; crucial for load hauling.
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Rolling Resistance: Resistance from vehicle weight; needs to be calculated for efficiency.
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Penetration Resistance: Effort to pull a tire sunk into a surface; affects total power.
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Grade Resistance: Force needed to overcome gravity on slopes; essential in route planning.
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Grade Assistance: Reduced power when moving downhill; important for power management.
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Co-efficient of Traction: Impacts usable power; based on the surface conditions.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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A machine with a gross weight of 50 tons and a rolling resistance of 28 kg/ton has a total rolling resistance of 1400 kg.
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On a 4% slope, using the guideline of 10 kg/ton for grade resistance, a 15-ton machine would require an additional 600 kg of tractive effort.
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If the usable power from a tractor is 7000 kg and 1500 kg is used for resistance, 5500 kg is available to tow a load.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Rimpull and drawbar pull, help machines move with power full.
📖 Fascinating Stories
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Imagine a heavy tractor on a hill; it needs extra push, even when still - that’s grade resistance, you see, pulling uphill takes more energy.
🧠 Other Memory Gems
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R R G A: Rolling Resistance, Grade Resistance, Grade Assistance.
🎯 Super Acronyms
RPG
- Rimpull - Penetration - Grade; a guide to remember key forces.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Rimpull
Definition:
The tractive force developed at the point of contact between the tire and the ground, mainly for wheeled machinery.
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Term: Drawbar Pull
Definition:
The equivalent concept of rimpull for tracked or crawler-mounted machines.
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Term: Rolling Resistance
Definition:
The force opposing the motion of a vehicle caused by the weight of the vehicle.
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Term: Penetration Resistance
Definition:
The effort required to move a tire that sinks into a surface, calculated by the depth of penetration.
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Term: Grade Resistance
Definition:
The additional force required to move a vehicle up a slope against gravity.
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Term: Grade Assistance
Definition:
The decrease in power needed for a vehicle moving down a slope due to gravitational assistance.
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Term: Coefficient of Traction
Definition:
The measure of grip between the tire (or track) and the surface which affects usable power.
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Term: Usable Power
Definition:
The actual power that can be used for work after overcoming resistance.