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A short class with Sarah and her students. The other ways are under More.
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Let's start with the concept of swell factor. Who can tell me what the swell factor is?
Is it the difference in volume between bank and loose soil?
Exactly! The swell factor is the ratio of loose dry unit weight of the material to the bank dry unit weight. It helps us understand how much the material expands when it's disturbed. Did you know that for push-loaded scrapers, this swell factor increases by 10% due to additional compaction?
Why does the compaction change the swell factor?
Great question! The pressure from the pusher compresses more material into the scraper bowl, increasing its density, thus affecting the swell factor.
Remember, an easy way to recall this is: "More push means more compact, 10% is a handy fact!"
Got it! So we need to use the adjusted swell factor whenever we're calculating loads.
Absolutely, let's summarize: the swell factor critical for understanding the volume of loaded materials and it can vary based on the operational method.
Now, let's dive into calculating the total resistance that a scraper faces during operation. Who remembers how we assess this resistance?
We need to look at both the rolling resistance and the grade resistance!
Exactly! Rolling resistance remains constant at 50 kg per ton. Now, if we consider the grades of 5%, 3%, and -3%, how would we convert these grades into kg per ton?
We multiply the grade percentage by 10 to convert to kg per ton!
Correct! So, for example, a 5% grade equals 50 kg per ton. This conversion helps us assess different resistance segments along the haul route.
Let’s remember: "Grade up, resistance up; grade down, resistance down!" This can help when determining overall loads.
So we need to calculate it segment-wise for accuracy?
Yes, breaking it into segments gives us a clear view of the travel resistance at each step!
Moving on, how do we balance the work between scrapers and pushers? Anyone remember how their cycle times play into this?
The pusher cycle time is usually smaller, right? So more scrapers can be served by one pusher.
Exactly! The ratio of cycle times helps determine how many scrapers a pusher can effectively manage. What’s the formula we use?
It’s the scraper cycle time divided by the pusher cycle time!
Correct! And what’s a typical balanced number of scrapers we've discussed?
It can be 5.68 scrapers per pusher based on our calculations!
Right! Since we can’t have a fraction, we have to round it up or down based on operational economics. Always think about balancing efficiency!
So, we could round to either 5 or 6 and then assess our productivity?
Exactly! Remember, efficiency in operations comes from optimal balancing!
Significantly influences the volume and weight of material during transportation.
Involves all phases of the scraper's operation, from loading to hauling and unloading.
Understanding both rolling and grade resistance is essential to estimating accurate travel times.
When we load, we must find, swell factor helps the weight unwind.
Picture a scraper load getting heavier; a pusher's push compresses the earth, making it denser and altering the swell factor by 10%.
RGR - Resistance, Grade, and Rolling are the keys to knowing how much weight you’ll be hauling.
RADIUS: Resistance And Distance In Unit Scrapers for efficient calculations.
Term
What is the swell factor?
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Term
What does cycle time include?
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The ratio of loose dry unit weight of a material to its bank dry unit weight, indicating volume change upon disturbance.
The time taken for a machine to complete one full cycle of operation, including loading, hauling, and dumping.
The resistance encountered by a machine while moving across a surface, often expressed in kg per ton.
The resistance experienced due to inclination or decline in the surface gradient during hauling.
This section focuses on calculating travel time within earthmoving operations, specifically using scrapers and pushers, emphasizing productivity and cycle time considerations.
In this section, we explore the methodologies for calculating the travel time of scrapers in earthmoving operations, including how to balance the workload between scrapers and pushers to enhance efficiency. Key factors such as swell factor, resistance types, and cycle times are discussed in detail.
This section delves into the important topic of travel time calculation for scrapers used in earthmoving operations. It begins by defining the concepts of productivity and the significance of estimating cycle times for related machines, including pushers.
The section outlines the specifics of working with scrapers, emphasizing the influence of factors such as the swell factor (increased by 10% for push-loaded scrapers due to compaction) and rolling resistance (noted as 50 kg per ton). The cycle time is derived from the combination of loading, dumping, and turning times, culminating in the overall efficiency of the operation.
To accurately assess the travel speed, the resistance along different sections of the haul route is computed, reflecting the varying gradients and their conversion into kg per ton. Additionally, the process of segmenting the haul cycle into distinct distances is explained to facilitate precise time calculations.
Finally, the techniques for balancing scrapers and pushers are presented, highlighting how optimal relationships and timing between these interdependent machines can lead to minimized operational costs and maximized productivity.