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A short class with Sarah and her students. The other ways are under More.
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Today, we will discuss the swell factor. Can anyone tell me what a swell factor represents in earthmoving?
Isn't it the ratio between loose and bank dry unit weight?
Exactly! Now, for dry earth, the swell factor is given as 0.80. When using pushers, we must remember that this can increase by 10% due to additional compaction. So what would be the swell factor we consider when working with push-loaded scrapers?
That would be 0.88, right?
Great memory! This is crucial for calculating effective load volumes. Remember: Swell Factor = Loose Dry Unit Weight / Bank Dry Unit Weight.
So it's important to adjust the swell factor based on the loading technique!
Absolutely! This affects how much material we can effectively load into the scraper before hitting diminishing returns.
To summarize, the swell factor impacts loading capacity significantly, especially when pushers are involved.
Let's now move on to calculating cycle times. What are some components we need to consider for a scraper's cycle time?
We need to look at loading time, dump time, travel time, and turn time, right?
Exactly! Based on our earlier problem statement, can anyone give me the average loading time?
That would be 0.80 minutes.
Correct! And the average dumping time is 0.37 minutes. To find the total cycle time, we sum these along with travel times. Can anyone calculate it?
If we add those up, we will still need to factor in the traveling times as well, like the 6.1 minutes we derived earlier!
So it would end up being around 7.78 minutes in total for the scraper cycle!
Excellent! Your understanding here will ensure that we have the right timing for balancing scraper and pusher operations.
Now, let’s discuss the concept of balancing scrapers and pushers. Why do we need to balance these machines?
To avoid delays and ensure that one doesn't wait too long for the other?
Exactly! If one pusher can serve multiple scrapers, how do we calculate the balanced number of scrapers?
We take the cycle time of the scraper divided by that of the pusher!
That's right! With a scraper cycle of 7.78 minutes and a pusher cycle of 1.37 minutes, what does that give us?
That would be approximately 5.68 scrapers, but we have to round it!
Correct! Based on operational efficiency, we could serve either 5 or 6 scrapers. Remember, it’s important to evaluate the economics of each to make a decision.
To summarize, balancing scrapers and pushers helps minimize waiting times and maximize productivity.
Represents the change in volume of soil when disturbed, important for load calculations.
Total weight of the scraper including the load, vital for calculating operational capabilities.
Duration taken to complete one full operation cycle, affects productivity estimates.
Important strategy to optimize productivity by aligning the operational efficiencies of scrapers and pushers.
To remember swell factor's might, load is light and bank is tight.
Imagine a baker measuring flour. The fluffier the flour, the more it weighs. This is like the swell factor; the well-packed bank volume fills less than the loose fluff.
Remember SCRAP for loading details: Swell, Capacity, Resistance, Average loading, Pusher cycle.
S.C.R.A.P. = Swell factor, Capacity of scrapers, Resistance, Average loading time, Pusher times.
Term
Swell Factor
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Term
Cycle Time
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Term
Gross Weight
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The ratio of loose dry unit weight to bank dry unit weight of soil, indicative of expansion when the soil is disturbed.
The time taken for a complete operation cycle of a machine, including all phases of loading, travel, and dumping.
The total weight of the machine, including its empty weight and the weight of the load it carries.
The duration needed for a pusher to assist a scraper in completing the loading phase.
This section focuses on the estimation of productivity for scrapers, including calculations involving material properties, machine capacities, and operational efficiencies.
In this section, the productivity estimation of scrapers is explored through practical calculations. Key concepts such as swell factors, machine weights, and haul routes are discussed, along with sample problems to balance the use of scrapers and pushers to enhance productivity and minimize costs.
In this section, we delve into the productivity estimation for scrapers used in construction. The discussion is centered around operational parameters and physical properties of materials, such as the unit weight of dry earth and the relevant swell factors affecting the hauling capacity of scrapers. The combination of scrapers and pushers plays a vital role in enhancing productivity during earth-moving operations.