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Load the truck: excavator and fleet

Short answer

Divide the truck's payload by what each pass lifts (bucket × fill × density) to get the passes; times the cycle, the loading time. Trucks so the excavator never waits = (loading + round trip) ÷ loading, rounded up. Example with assumptions: PC300-8M2 in common earth with a HD325-7 → 12 passes; with a 24 s cycle that's 4.8 min of loading, and with a 12 min trip it takes 4 trucks. Fewer and the excavator stands idle; more and they queue.

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The rule you're practising

  1. Load per pass = bucket × fill factor × loose density.
  2. Passes per truck = as many as fit without exceeding its payload or its body volume.
  3. Loading time = passes × excavator cycle.
  4. Trucks so it never waits = ⌈(loading time + haul, dump and return) ÷ loading time⌉.
  5. Output = bucket × fill × (3,600 ÷ cycle) × the share of the hour it actually loads.

Where each number comes from

  • Excavator buckets; truck payload and body volume.Source: Komatsu spec sheets in the catalog. The HD405-7 doesn't publish its body volume: only its payload limits it.
  • Density and fill factor.Source: the site's bucket table (Komatsu Handbook + industry standard).
  • Output and passes formula.Source: the site's guide 'How many m³ per hour does an excavator move?'.
  • Starting cycle (24 s) and trip (12 min).Source: your assumptions: time the cycle on site (24 s is the guide example's) and the trip depends on your distance and road.

FAQ

How many trucks does an excavator need?

Enough to cover the full round: (loading time + haul, dump and return) ÷ loading time, rounded up. Fewer and the excavator waits; more and trucks queue without adding output.

How many passes does it take to fill a truck?

Divide the truck's capacity by the load per pass (bucket × fill × loose density) and keep the passes that don't exceed payload or body volume. With light material the body usually limits; with heavy, the weight.

What is the excavator cycle and how do I measure it?

It's the time to load, swing, dump and return. Time 20 to 30 cycles in a row on your real job and average them: it's the number that moves the result the most.

Guide: excavator m³ per hourGuide: articulated or dump truckFleet study with your dataAll simulators