1.1. Angle of Swing and Cycle Time

The angle of swing is nothing but the horizontal angle between the digging and the dumping position between the loading and the dumping position.

The angle of swing refers to the horizontal angle created when the bucket of an excavator swings from its loading position to its dumping position. This angle affects how efficiently the excavator can work. A smaller angle means the excavator can operate faster because it doesn’t have to move as far to dump the load. The angle is considered to be optimal at 90 degrees, meaning the truck is aligned perfectly for loading and dumping.

Think of swinging a baseball bat. If you swing the bat directly over the plate (90 degrees), you hit the ball more effectively. If you have to swing out wider (greater than 90 degrees), it takes longer and is less efficient.

As the angle of swing increases, cycle time will increase, and productivity will decrease.

As the angle of swing increases beyond the ideal 90 degrees, the time it takes for the excavator to complete a cycle—swing to load, dump, and return—increases. This directly impacts how many cycles can be completed per hour, thus reducing overall productivity. A larger swing requires more movement, leading to longer waits between loading and unloading.

Imagine playing a game of catch but having to run farther away every time before throwing the ball. The further you are from your partner, the longer it takes each time to get into position and throw, just like the increased cycle time with a larger angle of swing.

The ideal condition for shovel productivity is based on a 90-degree swing.

In ideal conditions, where the excavator's bucket swings at a 90-degree angle, there is optimal efficiency and productivity. This condition assumes the excavator is operating close to the truck, minimizing the distance the bucket needs to swing and thereby reducing the cycle time. It allows for the greatest number of loads to be moved in a given period.

Think of a conveyor belt that transports boxes. When the boxes are placed at the right spot on the belt, they move smoothly and quickly to the next station. If they are placed too far or at an angle, they take longer to get there—just like the excavator's ideal working conditions.

Adjustment factors depend on the actual height of cut of material in your project site and the angle of swing.

When calculating productivity, it's crucial to consider both the height of the cut and the angle of swing. If the actual height differs from the optimum height, correction factors must be applied. For example, if the cut height is lower than expected, productivity decreases, and you adjust calculations according to this factor.

Imagine trying to fill a container with water using a cup. If you only fill the cup halfway (lower than expected), it will take more trips to fill the container, just as lower cut heights reduce the effectiveness of the excavator, requiring more cycles for the same volume of material.

There should be some space left for the tail swing of the shovel, known as truck spotting clearance.

While it is important to place the truck close to the excavator to minimize swing and maximize efficiency, there needs to be adequate space for the shovel’s tail to swing without obstruction. Not allowing for this clearance can lead to accidents or inefficiencies, as the machine might collide with the truck, halting operations.

Imagine a dancer performing on stage. If the performance space is too cramped, the dancer may bump into props or other dancers, disrupting the flow of the performance—similar to the excavator needing room to operate effectively without bumping into obstacles.

The time needed for the loaded truck to leave its position and for a new empty truck to take its place is called haul unit exchange time.

Haul unit exchange time is significant in determining the efficiency of an excavator's operation. If trucks are not readily available, the excavator will have to wait, increasing the total cycle time and reducing productivity. Efficient management of this time is critical to ensure that the excavator always has a truck available to load.

Consider a busy restaurant kitchen where waitstaff must deliver food while chefs prepare meals. If the servers are delayed in returning to get more meals, the kitchen gets backed up, just like if trucks aren’t available for the excavator, it will slow down the entire operation.

The production of shovel depends upon the heaped volume of your bucket, adjusted with the bucket fill factor, divided by the cycle time.

To estimate the productivity of an excavator, one needs to consider the volume of material the bucket can hold (heaped volume) and adjust for how effectively that volume can be filled (bucket fill factor). This total is then divided by the cycle time to find out how much material can be moved in a specified time frame. Increasing bucket efficiency or decreasing cycle time boosts overall productivity.

Think of filling a backpack with books. If the backpack can hold 10 books but is only filled with 6 due to their sizes (fill factor), you aren’t maximizing its capacity. If it takes you 5 minutes to fill it and grab a new one, knowing how many you can fill every hour helps you understand your speed, just like calculating how much an excavator can move.

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