4.2 - Techniques for Reducing Rolling Resistance
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Scraper-Pusher Dynamics
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Welcome, everyone! Today, we'll explore how different configurations of scrapers and pushers impact productivity. Can anyone tell me what happens if there are too few scrapers?
If there are too few scrapers, the pusher might have to wait, which could slow down productivity.
Exactly! The pusher becomes idle if there aren’t enough scrapers. When we have 5 scrapers, for instance, the production rate depends heavily on their availability. Can anyone help me recall the production formula we used?
It was based on the efficiency, number of scrapers, and volume per load, right?
Yes! The formula is: Production = (Efficiency * Number of Scrapers * Volume per Load) / Cycle Time. Great work!
Production Calculations
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s do a quick calculation. What is the production rate for 5 scrapers if we use a bowl volume of 19.82 bank cubic meters?
If the cycle time is 7.78 minutes and the efficiency is 50 minutes per hour, we can calculate it!
Right! This gives us a production rate of 636.89 bank cubic meters per hour. Now, what happens if we add a sixth scraper?
Then the production rate increases to 723.36 cubic meters, showing a higher productivity rate.
Exactly! Although more scrapers increase productivity, we also need to consider cost.
Cost Analysis
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s discuss costs. What did we find out regarding the unit production cost for the scrapers?
The cost for 5 scrapers was ₹44.12 per cubic meter, while it rose to ₹45.07 for 6 scrapers.
Exactly! This illustrates that while productivity may increase with more scrapers, costs can also rise, impacting overall project economics.
So, choosing the right number of scrapers is crucial for balancing productivity and costs!
Well summarized! Always remember the balance between productivity and cost.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section elaborates on the importance of balancing the number of scrapers and pushers to achieve maximum productivity while minimizing the production costs. It highlights calculations needed to estimate production rates and costs for configurations with varying numbers of scrapers, focusing on optimizing operational efficiency.
Detailed
In this section, we analyze the economics of utilizing 5 and 6 scrapers with a single pusher, discussing the impact of varying numbers of scrapers on productivity and unit production costs. As the number of scrapers increases beyond the balanced number, the control shifts from scrapers to the pusher, affecting cycle times and operational efficiency. Detailed calculations are provided to derive the production rates in bank cubic meters per hour, revealing that increasing the number of scrapers generally increases productivity up to a point where cost considerations must also be factored in. The comparison of costs per bank meter cube between different configurations shows that 5 scrapers yield a lower cost compared to 6. The section concludes with insights into the most effective use of scrapers for enhanced productivity.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding Rolling Resistance
Chapter 1 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Rolling resistance is the force that opposes the motion of a vehicle or equipment due to deformation of the surface it rides on. Techniques to reduce rolling resistance include improving the quality of the haul route, maintaining the terrain, and choosing the right equipment.
Detailed Explanation
Rolling resistance acts like friction that slows down machines, particularly scrapers. By enhancing the surface where equipment travels, such as filling in pits and smoothing out rough areas, we can help reduce this resistance. Selecting appropriately sized machinery that matches the terrain can also lower rolling resistance, making machines more efficient.
Examples & Analogies
Think of rolling resistance like trying to roll a ball on various surfaces. If the surface is smooth like a gym floor, the ball rolls easily. But if it’s a bumpy, uneven path, it slows down. Just like how you would want to smooth out a path for the ball to roll freely, we want to create better paths for our heavy machinery.
Maintenance of the Haul Route
Chapter 2 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Interventions to maintain the haul route can significantly reduce rolling resistance. This includes regular grading, filling in potholes, and ensuring drainage pathways are clear to prevent erosion.
Detailed Explanation
Maintaining the haul route involves consistent efforts to keep the path smooth and free from obstacles. This can be achieved through the use of graders or bulldozers to flatten and clear the road. When the surface is well-maintained, machinery experiences less strain, which can lead to faster cycles and reduced fuel consumption.
Examples & Analogies
Imagine riding a bicycle on a well-paved road versus a gravel path. You can travel much faster and easier on the paved road because there is less resistance. Similarly, if machines operate on well-maintained routes, they can work more efficiently.
Selecting the Right Equipment
Chapter 3 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Choosing the appropriate size and type of scraper and pusher for specific job conditions can help reduce rolling resistance. A smaller or more efficient machine can perform better on specific terrains, requiring less effort.
Detailed Explanation
When picking equipment, it’s essential to consider the job’s requirements and the terrain. Using a machine that is too powerful may lead to wastefulness, while an undersized machine may struggle, leading to increased rolling resistance. By selecting equipment that is suited for the task, we can achieve higher efficiency and lower operational costs.
Examples & Analogies
Consider a backpacking trip: if you carry a light, appropriately-sized backpack, you can hike longer without feeling weighed down. But if you bring a heavy, bulky pack for a light day hike, it becomes burdensome, just like using oversized equipment for a simple task increases our workload unnecessarily.
Optimizing Load Conditions
Chapter 4 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Ensuring that scrapers operate with loads that are appropriate for their capabilities optimizes efficiency and reduces rolling resistance. Overloading can increase resistance and lead to delays.
Detailed Explanation
Each machine is designed to carry a specific load. Exceeding this load can cause mechanical failure or inefficiencies. If scrapers are used within their designed load limits, they can perform tasks faster and with less energy, thereby minimizing rolling resistance.
Examples & Analogies
Think about carrying grocery bags. If you load them with too much weight, you’ll struggle and may even drop them, leading to a longer trip and more effort. Similar to this, equipment operates best when it isn’t overloaded.
Handling Terrain Effectively
Chapter 5 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Operating scrapers on downgraded terrain can also minimize rolling resistance. When loading can occur on a decline, it reduces the energy required and increases efficiency.
Detailed Explanation
Using the natural slope of the land can help scrapers perform their tasks more easily. When scrapers load materials on a downgrade, gravity assists in moving the load, which decreases the strain on the equipment and leads to faster operation.
Examples & Analogies
Imagine pushing a cart down a hill. It’s much easier than pushing it up because gravity helps you. In the same way, if scrapers can utilize gravity to aid in their operation, they will use less energy and time.
Key Concepts
-
Production Control: Scrapers control production based on their availability and cycle time.
-
Cost Efficiency: Selecting the optimal number of scrapers balances productivity and production costs.
-
Cycle Time: The time taken for scrapers to complete a loading, hauling, and dumping cycle.
Examples & Applications
Using 5 scrapers produces 636.89 bank cubic meters per hour, while 6 scrapers improve this to 723.36 bank cubic meters.
Costs per bank cubic meter increase from ₹44.12 with 5 scrapers to ₹45.07 with 6 scrapers.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Scrapers five, they work in a hive, pushing and pulling, making us thrive.
Stories
Imagine a construction site, where scrapers and pushers unite. Five scrapers toil, while a pusher can smile, waiting to assist, making the job worthwhile.
Memory Tools
Remember SPCC: Scraper Production Cost Control - to guide on scraper usage and cost efficiency.
Acronyms
SCOPE
Scraper Control Over Production Efficiency
an acronym to recall the balance needed.
Flash Cards
Glossary
- Scraper
A type of equipment used for earthmoving, capable of loading, hauling, and dumping materials.
- Pusher
A machine that assists in pushing scrapers to enhance loading efficiency.
- Production Rate
The amount of material produced in a given time frame, commonly expressed in bank cubic meters per hour.
- Unit Production Cost
The total costs incurred to produce a unit of output, measured in cost per bank cubic meter.
- Efficiency
A measure of how effectively a machine performs its intended tasks, often expressed as a percentage.
Reference links
Supplementary resources to enhance your learning experience.