1.1. Components of Cycle Time

Cycle time = LT + HT + DT + RT + ST + TT + ADBT (Where, LT-Load, HT-Haul, DT-dump, RT-Return, ST-Spot, TT-Turn, ADBT- Acceleration, Deceleration and braking)

Cycle time is the total time taken to complete one full operation cycle of a machine. It includes several components: load time (LT), haul time (HT), dump time (DT), return time (RT), spotting time (ST), turn time (TT), and the time for acceleration, deceleration, and braking (ADBT). Each of these components contributes to the overall time taken in operating machines like scrapers in construction or mining projects.

Think of cycle time like cooking a meal. Each step in the cooking process—like preparing ingredients, cooking, serving, and cleaning up—represents a component of your cycle time. Just like a meal takes time to prepare and serve, machinery in construction has specific tasks that take time to complete.

You can split the cycle time into 2 parts: fixed time and variable time. Fixed time does not depend on travel distance and includes loading, dumping, turning, acceleration, deceleration, and braking. Variable time is dependent on haul and return distances.

Cycle time can be divided into fixed and variable components. Fixed time remains constant regardless of the distance traveled and encompasses tasks like loading, dumping, and the mechanical operations of the scraper. On the other hand, variable time is influenced by the distance traveled during the haul (moving material from one location to another) and return trips. This means that the more distance covered, the more time it takes.

Imagine a car trip. The time spent getting in the car, buckling your seatbelt, and starting the journey is fixed—it doesn’t change based on how far you’re going. However, the driving time does depend on the distance you travel. If you have a long way to go, it will take longer, just like how a scraper takes longer for variable times based on how far it needs to haul material.

The loading time of the scraper is fairly consistent irrespective of the scraper size due to assistance from a pusher. The average load time for a pusher loaded scraper in common earth is about 0.8 minutes.

Loading time for scrapers is generally uniform, regardless of their size, primarily because they are assisted by a pusher. This support means that varying sizes of scrapers will have similar loading times due to the additional force provided by the pusher. For common earth material, the average loading time is approximately 0.8 minutes.

Think of loading a suitcase. It doesn’t take significantly longer to pack a larger suitcase if you have someone helping you. The assistance speeds up the process, just like a pusher helps the scraper load material faster. Even if the suitcase is larger, the loading time can still be quite similar when help is involved.

Loading scrapers to maximum capacity will reduce rather than increase the rate of production due to the resistance encountered by existing material in the bowl. This is called the law of diminishing returns.

There is a common misconception that loading a scraper to its fullest capacity will always yield the best production results. However, past studies have shown that after reaching a certain fill level (around 80-85%), the loading rate decreases because the material already in the bowl starts to resist the addition of new material. This is an example of the law of diminishing returns; loading beyond a certain point is counterproductive.

Consider trying to fit too many groceries into a shopping cart. Initially, you can add items easily, but once the cart gets full, adding more makes it difficult, and it might even spill over or make it harder to push. This is similar to scrapers—overloading leads to inefficiency.

Haul and return time depend on travel distance and machine speed. Maintaining the haul route is essential to reduce cycle time and improve productivity.

Haul and return times are essential components of cycle time and vary based on how far material needs to be moved and the speed of the machinery involved. To ensure efficiency, it is crucial to maintain the haul route, as this minimizes resistance and allows machines to operate more quickly, which reduces overall cycle time.

Think of it as a bicycle ride. If the road is smooth and well-maintained, you can cycle quickly and efficiently. However, if the road is rough with potholes, it will take much longer to get to your destination. Just like smoothing out a road for bicycles, maintaining a haul route for scrapers helps improve their travel efficiency.

Dump time depends on scraper size, material type, and constraints in the dumping area. Larger scrapers generally need more time to dump, especially if the site is congested.

Dump time varies significantly based on several factors: the size of the scraper, the material being dumped, and the conditions of the dumping site. Bigger scrapers naturally require longer to unload, and if the dumping area is crowded or has obstacles, it may take even longer due to waiting and maneuvering.

Imagine trying to unload a large moving truck in a tight garage versus an open parking lot. If it’s crowded, you’ll take more time getting everything out. The same applies to scrapers and their dumping times.

Turn time is generally independent of scraper type. However, turning in the cut area takes longer than in the fill area due to congestion.

Turn times do not typically vary with the scraper itself. However, a scraper turning in a congested cut area often takes longer than in a less crowded fill area because there are more obstacles and equipment in the cut zone that may impede movement.

Consider turning a car in a busy parking lot filled with people and other cars versus a wide-open road. It’s much easier and faster to turn in the open space, while in the crowded lot, you may need to stop and adjust your angle, adding time. This is similar for scrapers when turning in different work areas.

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