Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we're talking about the cycle time calculation, which is critical for estimating productivity in earthmoving projects. Can anyone tell me what we mean by 'ideal conditions'?
I think ideal conditions refer to situations where everything works perfectly as planned, like operating for a full hour.
Exactly! Ideal conditions often mean 60 minutes of effective working time. However, if a bulldozer only works for 50 minutes, we need to apply what factor?
That's the job efficiency correction factor, right?
Yes! The job efficiency correction factor adjusts our calculations to reflect actual operations. Remember the acronym 'JE' for Job Efficiency.
So how do we calculate that?
Good question! You would divide the actual working minutes by 60. So, in this case, it would be 50 divided by 60, which equals approximately 0.83.
What does that mean for productivity?
It means our productivity estimate will be reduced by this correction factor. Great discussion on job efficiency!
Next, let's consider soil density. Who remembers the standard density for our productivity curves?
It's 1365 kg/m³.
Correct! Now, if our project soil is denser, say 1750 kg/m³, what must we do with our calculations?
We need to apply a correction factor.
Right again! And why is this adjustment necessary?
Because denser soil makes it harder for the bulldozer to push, reducing productivity.
Exactly! The correction for increased soil density would typically be less than 1, indicating reduced productivity. Always keep soil density in mind!
Moving on to operator skill. If the operator’s skill is average versus excellent, what impact does that have?
The productivity would go down since the less skilled operator might not use the machine efficiently.
Exactly! This is another situation where we apply a correction factor of less than one. Can anyone give me an example of a material type affecting productivity?
Non-cohesive silty sand?
Spot on! So, how do both operator skill and material type affect productivity when combined?
We multiply correction factors together, right?
Precisely! This combined effect may significantly reduce our expected productivity. Always remember each factor's impact and to apply it systematically!
Let's talk about visibility and slope. If visibility is poor, what impact does that have on the bulldozer's operation?
It would probably decrease productivity since the operator can't see well.
Correct! Visibility adjustment is another correction factor, usually less than one. How about slope? What happens when moving downhill?
The productivity increases since gravity helps!
Exactly! For downhill slopes, the correction factor might be greater than one, enhancing productivity. Can someone summarize how we evaluate these factors graphically?
By referring to the curves from the equipment handbook that relate factors to productive output!
Right again! Excellent work discussing visibility and slope influences!
Understanding cycle time is crucial in productivity estimation.
These factors adjust theoretical productivity to reflect real conditions.
Effectively understanding job efficiency allows for better accuracy in estimations.
Soil properties play a major role in affecting equipment performance.
The operator’s craft can either enhance or decrease output efficiency.
If a bulldozer's maximum productivity is 114.68 loose cubic meters per hour under ideal conditions but is working in a situation with a job efficiency of 83%, the effective productivity is reduced to 95.20 loose cubic meters per hour.
For a project with a soil density of 1750 kg/m³ (compared to the standard of 1365 kg/m³), a correction factor is applied, resulting in a productivity estimate lower than initially calculated.
If visibility is low and soil is dense, productivity decline can be quite immense!
Imagine a bulldozer struggling uphill in foggy conditions. The operator, unsure of the path, stops often, leading to decreased productivity - a perfect lesson on how conditions matter!
Remember the acronym C-JSOM (Costs, Job Efficiency, Soil, Operator, Material) for factors influencing cycle time.
CROP for Cycle time Reduction using Optimal Processes, to remember the important factors.
Term
Cycle Time
Click to flip
Term
Correction Factor for Job Efficiency
Click to flip
Term
Soil Density Correction Factor
Click to flip
The total time taken to complete a cycle of operation, including dozing, returning, and maneuvering time.
A numerical adjustment applied to the productivity estimate to reflect actual working conditions.
The ratio of actual working time to theoretical maximum working time, expressed as a percentage.
The mass per unit volume of soil, which can affect the productivity of earthmoving operations.
The proficiency level of the operator, which influences the overall effectiveness and efficiency of equipment operation.
This section discusses the factors impacting cycle time calculation for earthmoving operations, emphasizing correction factors related to soil density, operator skill, and job efficiency.
In this section, various factors influencing the cycle time calculation in earthmoving operations are analyzed. These include soil density variations, operator skills, gear transmission modes, and correction factors like job efficiency and the type of material being moved. Correction factors are crucial for adjusting maximum production values derived from manufacturer curves to align with actual project conditions.
In earthmoving operations, accurately calculating cycle time is essential for estimating productivity and costs. This section specifically addresses the correction factors needed to adjust theoretical productivity values based on ideal curve conditions (such as those provided by equipment manufacturers) to the realities of specific job site conditions.
Ideal Conditions: The curves presented are only valid under ideal conditions, including 60 minutes of effective work per hour. However, if a bulldozer operates for only 50 minutes, a job efficiency correction factor applies.
Soil Density Impact: The production values retrieved from the manufacturer's curve are based on specific soil densities. If the soil density in the project is higher (e.g., 1750 kg/m³ vs. the standard of 1365 kg/m³), a correction factor must be applied.
Operator Skills: The curves assume an ideal operator skill level. If the operator has average skills, the productivity will decrease, necessitating a correction factor of less than one.
Material Type: Non-cohesive materials like silty sand would reduce productivity, hence apply another correction factor.
Additional Correction Factors: Other factors such as visibility conditions, dozing methods, and grade slopes can also enhance or reduce productivity, necessitating further corrections based on actual project conditions.
These correction factors ultimately ensure a more accurate estimation of the unit cost of the earthmoving operation, essential for effective project budgeting and bidding.