1.6. Turn 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).

The cycle time in a machine operation includes several components: Loading Time (LT), Hauling Time (HT), Dumping Time (DT), Return Time (RT), Spotting Time (ST), Turning Time (TT), and the time required for Acceleration, Deceleration, and Braking (ADBT). Each element contributes to the overall efficiency and duration of the operation. For example, load time is how long it takes to fill the machine, while haul time is how long it takes to move the material to the dumping site.

Think of a delivery truck. The cycle time is the total time from when the truck leaves the depot to when it returns. The components would be the time taken to load parcels (load time), drive to the delivery point (haul time), drop off the parcels (dump time), and return back to the depot (return time). Each step is essential for ensuring the truck operates efficiently.

Basically, you can split the cycle time into 2 parts: fixed time and variable time. Fixed time is independent of travel distance, including loading, dumping, turning, and acceleration. Variable time includes haul and return times, which depend on travel distance and speed.

In understanding cycle times, they can be divided into fixed and variable components. Fixed times do not change regardless of how far the machine travels; they include activities like loading, dumping, and turning. Variable times, on the other hand, are affected by the distance travelled and the speed of the equipment. For instance, longer distances mean longer haul and return times.

Imagine a student riding a bike. The time it takes to pack their backpack (fixed time) does not change with how far they ride to school, but the journey time (variable time) does depend on whether their school is 1 mile or 5 miles away.

The loading time of the scraper is fairly consistent irrespective of size. The average load time for a pusher loaded scraper in common earth is about 0.8 minutes. However, loading scrapers to maximum capacity can reduce production due to resistance within the bowl, known as the law of diminishing returns.

When loading a scraper, the time taken remains mostly the same regardless of the scraper's size because they are often assisted by a pusher. However, there is a limit to how much material can be loaded efficiently. Overloading can cause delays as the materials inside the bowl resist incoming loads, leading to lower overall productivity.

Imagine a suitcase that you are trying to pack. Initially, it's easy to add clothes, but as it starts to fill up, it becomes increasingly difficult to fit more items in. If you try to cram too much in, you might slow down the packing process and end up with a less organized suitcase.

The haul and return times depend on distance and speed, which can be influenced by site conditions. Maintaining the haul route is essential for reducing cycle time and improving productivity.

Haul and return times are critical components of cycle time that vary based on how far the machine needs to travel and how fast it can move. Keeping the route well-maintained minimizes resistance and allows for faster operation, directly affecting the machine's efficiency and output.

Consider a runner on a track. If the track is smooth and well-kept, the runner can maintain a quicker pace compared to a rough and bumpy path, where they would have to slow down due to obstacles or uneven terrain.

Dump time is influenced by the size of the scraper and the material handled, as well as site constraints that might require the machine to wait before dumping.

The time it takes for a scraper to dump its load depends on a few factors, such as the size of the scraper and the type of material being dumped. For instance, loose materials are easier and quicker to dump than sticky or heavy materials. Also, if the dumping area is congested with other machines, this can delay the process.

Think about a traffic jam when trying to exit a parking lot. If there are too many cars waiting, your exit (like dumping material) is delayed, regardless of how quickly you could proceed if the area were clear.

Turning time is generally consistent and not influenced by the scraper's size, but varies depending on whether the turn is made in the cut area or fill area, with longer times typically seen in the cut area due to congestion and other equipment.

While the size of the scraper doesn’t affect how long it takes to turn, the location plays a significant role. Turns made in areas where more machines are present (like the cut area) tend to take longer due to space constraints and the need to maneuver around other equipment.

This can be related to a car trying to make a turn in a busy parking lot versus an empty street. The parking lot requires careful navigation around parked cars, leading to longer maneuvering time, whereas a clear street allows for a quicker turn.

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