A Quantum Expert’s Guide to Excavation Costs and Cycle Times
Understanding how to calculate the cycle time of an excavator in a simple and clear way helps us figure out how efficiently an excavator works and how much it costs to move material.
What is Cycle Time?
The cycle time of an excavator is the time it takes to complete one full operation. This includes:
1. Digging: The bucket scoops up material like soil or gravel.
2. Swinging (Loaded): The bucket moves to where the material will be dumped.
3. Dumping: The material is emptied out of the bucket.
4. Swinging (Returning): The bucket swings back to start digging again.
Excavator cycle times are critical for forensic quantity surveyors when analysing construction productivity or resolving disputes as expert witnesses.
How is Cycle Time Measured?
Timing Each Step
If you can watch the excavator in action, you can measure each step with a stopwatch:
Digging Time: Start timing when the bucket begins scooping and stop when it is full.
Swinging (Loaded) Time: Time how long it takes for the bucket to swing to the dumping spot.
Dumping Time: Time how long it takes to empty the bucket.
Swinging (Returning) Time: Time how long it takes for the bucket to swing back to the digging position.
Add these times together to find the total cycle time:
Cycle Time = Digging Time + Swinging (Loaded) Time + Dumping Time + Swinging (Returning) Time
Using Reference Data
If timing isn’t possible, you can use data from trusted sources such as:
Caterpillar Performance Handbook: Includes average cycle times for different excavator models.
Manufacturer Manuals: Brands like Komatsu provide benchmarks for their machines.
Construction Textbooks: Books like Construction Planning, Equipment, and Methods by R.L. Peurifoy provide industry standards.
Forensic quantity surveyors often rely on these references when serving as expert witnesses to ensure accurate, evidence-based assessments.
Making Adjustments for Real Conditions
Cycle times can vary depending on:
Operator Skill: More experienced operators can work faster.
Material Type: Harder materials take longer to dig.
Swing Angle: A larger swing angle, like 180°, increases time compared to a smaller one, like 90°.
Site Conditions: Weather, space, and visibility can all have an impact.
These factors are often crucial in forensic quantity surveying when investigating delays or inefficiencies.
Example: Calculating Cycle Time
Let’s say you observe these times:
Digging: 6 seconds
Swinging (Loaded): 4 seconds
Dumping: 2 seconds
Swinging (Returning): 3 seconds
The total cycle time is: 6 + 4 + 2 + 3 = 15 seconds
Why is Cycle Time Important?
Knowing the cycle time helps calculate how much material an excavator can move in an hour, which is called the production rate. This is important for:
Checking how efficient the excavator is.
Identifying delays or inefficiencies.
Working out costs for a project.
The formula to calculate productivity is:
Production Rate (m³/hr) = (Bucket Capacity (m³) × 3600) ÷ Cycle Time (s) × Efficiency Factor
Example: Calculating Production Rate
Bucket Capacity: 0.5 m³
Cycle Time: 15 seconds
Efficiency Factor: 0.85 (accounts for breaks and repositioning)
Production Rate = (0.5 × 3600) ÷ 15 × 0.85 = 102 m³/hr
How Cycle Time Links to Costs
Once you know the Cycle Time, you can calculate how much it costs to move one cubic metre of material.
Cost calculation formula:
Cost per m³ = Hourly Operating Cost of Excavator ÷ Production Rate (m³/hr)
Example: Calculating Cost per m³
Hourly Operating Cost: $120/hr
ProductionRate: 102 m³/hr
Cost per m³ = 120 ÷ 102 = $1.18/m³
This means it costs approximately $1.18 to move one cubic metre of material.
Conclusion
Understanding cycle time helps us work out how productive an excavator is and how much it costs to move material. This information is crucial for planning projects, finding inefficiencies, and supporting claims or disputes.
Forensic quantity surveyors often analyse excavator cycle times as part of their work as expert witnesses, ensuring clarity and accuracy in construction-related cases.
By following these simple steps, you can explain and calculate the key details clearly and effectively while considering the role of cycle time in construction analysis.
At Accura Consulting, our team of experts work with clients to create a tailored solution to problems. If you have an issue and want expert support, get in touch.
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