A scraper is to haul earth from a pit to fill 0.4 km away. If it is working under averagefixed-time conditions of 2.2 minutes, with an average haul speed of 7 kmph , with operating factor of 0.8, the number of cycles which can effectively be performed per hour is nearly:

Concept:

To calculate the number of cycles a scraper can perform per hour, we need to account for the total cycle time (which includes the time to haul, return, and the fixed-time operations) and adjust for the operating factor.

Given Data:

• Haul Distance = 0.4 km
• Fixed time (loading, dumping, turning) = 2.2 minutes
• Average haul speed = 7 km/h
• Operating factor = 0.8

Calculate Hauling Time:

\( \text{Haul Time (in minutes)} = \frac{0.4}{7} \times 60 = 3.43 \, \text{minutes} \)

Calculate Return Time:

\( \text{Return Time} = 3.43 \, \text{minutes} \)

Total Time per Cycle:

\( \text{Total Cycle Time} = 2.2 + 3.43 + 3.43 = 9.06 \, \text{minutes} \)

Adjust for Operating Factor:

\( \text{Effective Time per Hour} = 60 \times 0.8 = 48 \, \text{minutes} \)

Calculate Number of Cycles:

\( \text{Number of Cycles} = \frac{48}{9.06} \approx 5.3 \, \text{cycles per hour} \)

The number of cycles that can effectively be performed per hour is approximately 5.4 cycles per hour.