Production is measured in terms of tons or bank cubic yards (cubic meters) of material a machine excavates and discharges, under given job conditions, in 1 h.

Production, bank yd³/h (m³/h) = load, yd³ (m³) X trips per hour

Trips per hour = working time, min/h / cycle time, min

The load, or amount of material a machine carries, can be determined by weighing or estimating the volume. Payload estimating involves determination of the bank cubic yards (cubic meters) being carried, whereas the excavated material expands when loaded into the machine. For determination of bank cubic yards (cubic meters) from loose volume, the amount of swell or the load factor must be known.

Weighing is the most accurate method of determining the actual load. This is normally done by weighing one wheel or axle at a time with portable scales, adding the wheel or axle weights, and subtracting the weight empty. To reduce error, the machine should be relatively level. Enough loads should be weighed to provide a good average:

Bank yd³ = weight of load, lb(kg) / density of material, lb/bank yd³ (kg/m³)

Equipment Required

To determine the number of scrapers needed on a job, required production must first be computed:

Production required, yd³ /h (m³/h) = quantity, bank yd³ (m³) / working time, h

No. of scrapers needed= production required, yd³/h (m³/h) / production per unit, yd³/h (m³/h)

No. of scrapers a pusher can load= scraper cycle time, min / pusher cycle time, min

Because speeds and distances may vary on haul and return, haul and return times are estimated separately.

Variable time, min= (haul distance, ft /88Xspeed, mi/ h) + (return distance, ft/88Xspeed, mi/h)

Or
= (haul distance,m/ 16.7Xspeed,km/ h) + (return distance, m/16.7Xspeed,km/ h)

Haul speed may be obtained from the equipment specification sheet when the drawbar pull required is known.