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A short class with Sarah and her students. The other ways are under More.
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Today we're going to discuss back-track loading. Can anyone tell me what happens once Scraper 1 is completely loaded?
The pusher detaches and goes back to get the next scraper?
Exactly! This process is called back-tracking. It allows the pusher to spot Scraper 2 and push it into the same direction. Can anyone describe why we call this the slowest loading method?
Because it takes time for the pusher to return?
That's right! The travel time adds to the overall cycle time, making it slower than other methods. Remember the acronym 'SLOW' for Back-Track Loading: S for 'Scraper', L for 'Load', O for 'Out', and W for 'Wait' - it emphasizes the waiting time in this method.
So, it’s slow because of the back and forth traveling?
Precisely! Now who can give an example of when back-track loading might be preferred despite its slowness?
Maybe in situations where it’s important to maintain the direction of cutting?
Yes, that's a great observation! Consistency in direction is a vital reason why many opt for this method. Let's summarize: Back-track loading is slow due to the return travel time but is valued for directional consistency.
Now, let's compare back-track loading with chain loading. Can someone explain what chain loading involves?
Chain loading allows the next scraper to come close to the pusher without needing to backtrack again.
Right! This reduced return time means chain loading has a shorter cycle time compared to back-track loading. Can anyone think of scenarios where they would choose chain loading?
For long narrow projects like roads where you're constantly pushing scrapers in a line?
Exactly! It's more efficient in such scenarios. Now, how does shuttle loading differ?
Shuttle loading works with fill areas on both sides, allowing scrapers to move in both directions?
Correct! This method also decreases cycle time. So, if we compare all three methods, which do you think is the best for consistency?
Back-track loading, because it keeps everything moving in one direction.
Great conclusion! Remember, each method serves different needs based on project specifics. Let’s summarize: Back-track is slow but directional, chain is efficient for long cuts, and shuttle uses dual directions.
Now, let's dive into calculating cycle times. Who can tell me the formula for pusher cycle time and its relation to scraper load time?
It’s Tp = 1.4 Lt + 0.25, where Tp is the pusher cycle time and Lt is the scraper load time.
Exactly! This formula helps in estimating how long it takes for the pusher to complete one full cycle. Why is this important?
It helps us balance the number of scrapers with the pusher to minimize delays.
Good point! Balancing is crucial. How can we determine how many scrapers one pusher can serve effectively?
By dividing the cycle time of the scraper by the cycle time of the pusher?
Exactly! This equation ensures we have the right number of machines working without making one wait on the other. Any thoughts on how this affects productivity?
If we balance them correctly, both will operate at maximum efficiency!
Correct! So, to summarize: Knowing how to calculate and balance cycle times is fundamental for productivity.
Involves the pusher returning to spot the next scraper after loading.
The total time taken by the pusher per cycle which includes loading and return time.
The balance between the number of scrapers and pushers directly affects operational productivity.
In scrub land, the pusher goes back, to push and load, that’s the track.
Imagine a diligent pusher who, after loading each scraper, turns back to fetch the next one, always on track, but taking much longer to get the job done.
Remember 'SLOW' - S for Scraper, L for Load, O for Out, W for Wait, all key features of back-track loading.
BTR (Back-Track Return): Reminds us of the essential return movement in the method.
Term
Back-Track Loading
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Term
Chain Loading
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Term
Cycle Time
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A loading method where the pusher detaches after loading a scraper and returns to push the next scraper.
A method where the next scraper waits near the pusher instead of requiring backtracking.
A loading method allowing scrapers to operate in both directions when there are fill areas in both directions.
Back-track loading involves a pusher returning to retrieve and push the next scraper after loading a previous one, making it the slowest but commonly used method in certain applications.
The back-track loading process entails the pusher detaching from a loaded scraper and returning to pick up the next scraper. Although it is the slowest method due to additional return travel time, it is preferred for its consistency in operation direction. Alternatives like chain and shuttle loading minimize return times but are less common.
In back-track loading, after the loading of Scraper 1 is complete, the pusher detaches and back-tracks to retrieve Scraper 2 for loading. Despite its reliance on additional travel time which makes it the slowest method, back-track loading is commonly adopted because it allows for consistent cutting direction, enhancing the efficiency of loading operations. The cycle time is primarily dependent on the project site specifics. In contrast, alternative methods like chain loading (suitable for long cuts) and shuttle loading (where scrapers may move in both directions) aim to reduce return times and enhance operational efficiency. The method's limitations in speed necessitate a balance between the number of scrapers and pushers to minimize waiting times and improve productivity.