6.3. Optimal Loading Time

So, once the loading of scraper 1 is completed, the pusher will back-track return back and spot the next a scraper, scraper 2 and start pushing it in the same direction. So, that is what is a back-track loading. So, first it is pushing the scraper 1, as a scraper 1 is completely loaded it will start moving on its own. Once the scraper 1 is loaded, your pusher will get detached and return that is backtracking, backtrack and it has to travel some distance and spot the next scraper 2. And then start pushing again in the same direction, it starts moving again in the same direction. So, that is what is your back-track loading method.

Back-track loading is a method used during material loading where the pusher moves the first scraper (scraper 1) to the loading site. Once scraper 1 is completely loaded, the pusher detaches and travels back to find the next scraper (scraper 2) to push it. This method involves extra travel time since the pusher needs to backtrack before pushing the next scraper.

Imagine a train that picks up passengers at a station. Once the train is fully loaded with passengers, it leaves the station and must return to pick up more passengers from the next station. This back-and-forth travel makes the overall journey slower, just like the pusher in back-track loading.

So, one limitation of this back-track loading method is it needs additional time for returning back backtracking. So, that is why we call this as a slowest method. So, this is the slowest of all the methods which we are going to discuss now. So, here you can see that the return time is more, return time is more because of the backtracking. So, everything the actual value will depend upon your project site.

The main drawback of back-track loading is the extra time it requires for the pusher to return after loading the first scraper. This makes it the slowest loading method. The overall efficiency can vary depending on the specific setup of the project site, but typically, the need for backtracking delays the process.

Consider a delivery person who needs to drop off packages at multiple locations. If after each delivery they must return to the depot before heading to the next location, each trip takes longer, much like how the pusher slows down in back-track loading by returning to pick up the next scraper.

But this is more commonly adopted by everyone because the people prefer the cutting in the same direction.

Despite its limitations, back-track loading is widely used because it allows workers to maintain the same cutting direction. This consistency simplifies the loading process and can be easier to manage for workers, as they don’t have to adjust their movements frequently.

Think of a chef who prefers to chop all vegetables in one consistent direction rather than switching directions each time they pick a new vegetable. This uniformity not only speeds up their work but also make it easier to maintain a rhythm in the kitchen.

The next method which we are going to discuss is your chain loading method. So, this we commonly follow for long cuts, long narrow cuts like your roads, we can follow the chain loading method, say here your pusher is pushing the scraper 1, once a scraper 1 is completely loaded the scraper 1 is now in fully loaded condition. Now your pusher will get detached from the scraper 1 and the pusher start pushing the next scraper.

Chain loading is used primarily for long and narrow cuts, such as those found in road construction. In this method, once scraper 1 is loaded, the pusher detaches and immediately starts pushing the next scraper (scraper 2) without needing to backtrack. This significantly reduces the return time.

Consider a factory assembly line where one worker passes a fully assembled product directly to the next worker without any need to return to their workstation. This transfer method speeds up production much like how chain loading improves efficiency in material handling.

But here is what happens the scraper 2 will come and wait near the pusher. Your pusher may not backtrack again; it may not return back again and spot the next scraper. So, the scraper 2 will come and wait near the pusher. So, this is commonly adopted in long roads, I mean long narrow cut like roads. So, here also since the returning time is reduced. So, you can say that the chain loading cycle time will be less.

In chain loading, while scraper 2 waits next to the pusher, it removes the need for backtracking. This leads to shorter cycle times since the pusher can almost continuously push scrapers without the delays caused by returning to locate new scrapers.

Like a relay race where one runner passes the baton to the next without stopping, chain loading allows scrapers to be loaded and moved in quick succession, enhancing speed and efficiency.

The next one is shuttle loading, this is not commonly followed, but you can follow it when you have 2 fill areas. That means you have a fill area in this direction as well as you have fill area in this direction. If you have fill areas in both the direction, then you can follow the shuttle loading.

Shuttle loading is a less common method implemented when there are two filling areas in opposite directions. In this instance, the pusher will move back and forth between the two fill areas, enhancing flexibility and reducing overall cycle time.

Imagine a shuttle bus that runs between two different neighborhoods. It goes back and forth, picking up passengers from both places without needing to stay at one endpoint. This flexibility allows for efficient management of passenger transfers, similar to how shuttle loading works.

So, when you compare all these 3 methods, you can see that your back-track is the slowest method, the cycle time is relatively higher because it has to backtrack or return to support the next scraper but your chain and shuttle loading though they are not commonly followed so, but they are having the lesser cycle time and we know the reasons already.

Overall, back-track loading is the slowest option due to the need for extra return trips. Chain and shuttle loading, while they may not be as frequently used, can lead to shorter cycle times because they reduce or eliminate backtracking.

Think of various modes of transportation in a city. Some routes are slower due to detours (like back-track loading), while direct routes or intertwined public transit (like chain and shuttle loading) can shorten travel times significantly.

So, to summarize back-track loading method is the slowest of all the methods because of the additional pusher travel time for backtracking on returning. But most commonly followed because people prefer cutting in same direction. Chain loading, it is suited for long and narrow cut, here the return time is reduced. Shuttle loading requests 2 separate fill areas in both directions.

Back-track loading, although slow due to return time, is popular for its directional consistency. Chain loading is efficient for road construction, and shuttle loading works well when there are two fill areas, allowing scrapers to operate in both directions.

Just like a navigation app that suggests the best route based on traffic conditions, choosing the appropriate loading method based on project requirements helps ensure efficiency and effectiveness during construction.

So, there is a thumb rule formula given by the caterpillar to determine the cycle time of the pusher, if you know the loading time of the scraper you can determine the cycle time of the pusher. Tp is the pusher cycle time and Lt is the scraper load time, the contact time of the pusher with your scraper during the loading phase of the scraper. So, if you know the loading time you can calculate the pusher time using this formula. Tp = 1.4Lt + 0.25.

To calculate the cycle time of the pusher (Tp), you need to know the loading time of the scraper (Lt). The formula Tp = 1.4Lt + 0.25 helps predict how much time the pusher will spend working based on the loading time of the scraper. This is useful for planning and efficiency measurement.

Think of it like budgeting time for a study session. If you know how long it takes to finish a chapter (scraper load time), you can estimate how long you need for your overall study (pusher cycle time), allowing you to plan your breaks and transitions effectively.

Another important thing as I mentioned earlier, we need to balance the interdependent machines, your scraper and pusher are interdependent machines, they work together. So, we have to balance them, we have to choose the correct number of scrapers and pushers, so that one need not wait for the other.

Balancing the number of scrapers and pushers is crucial for efficient operation. If one machine has to wait for the other, production slows down. Therefore, it is necessary to determine the appropriate number of each to minimize waiting times and maintain productivity in construction projects.

Like a well-coordinated dance duet, each dancer needs to know when to step forward or back to keep the performance flowing without pauses or stumbles. In construction, the balance between scrapers and pushers ensures that tasks are completed swiftly and efficiently.

So, how to find the number of scrapers which can be served by one pusher? As I told you pusher cycle time is less it is assisting the scraper only during the loading phase of the scraper. So, one pusher can serve even 4 to 5 scrapers. So, now how to determine the number of scrapers served by 1 pusher? So, N is the number of scrapers served by one pusher, it is equal to cycle time of the scraper divided by a cycle time to pusher. This gives you the balanced number. So, N = Ts / Tp.

To determine how many scrapers can be served by a single pusher, you calculate the ratio of the cycle time of the scraper (Ts) to the pusher’s cycle time (Tp). Typically, one pusher can effectively serve 4 to 5 scrapers, which maximizes efficiency without delays.

Think of a queue at a coffee shop where each barista can only serve a limited number of customers at once. Knowing how many customers each barista can handle helps ensure that there are enough baristas to keep the line moving without keeping anyone waiting for too long.

--