Question

A Power-shift crawler tractor is excavating tough clay and pushing it a distance of 21 m. The rated blade capacity is 7.0 LCM. Maximum reverse speeds are as follows: first range, 4.8 Km/h; second range, 9.0 Km/h, third range, 12.2 Km/h. Estimate the dozer production if management conditions and job conditions are excellent and good respectively.

Answer 1

Volume per cycle = 7 LCM

We can get production by,

Production = Volume per cycle x Cycles per hour x Efficiency

Efficiency for given condition = 0.83 (It is a standard value to be assumed)

Cycles per hour= fixed time + variable time

Fixed time = 0.05 min (For power shift crawler, it is a standard value to be assumed)

Calculation of Variable time,

Variable time = dozing time + return time

Dozing speed = 2.4 km/h (It is a standard value for excavating tough material for distance less than 30 m to be taken)

Dozing time = (21 m / 2.4 km/h) x (60/1000) = 0.525 min

Return speed = 9 km/h (For return of less than 30 m, maximum return speed of second range is taken as the return speed)

Return time = (21 m / 9 km/h) x (60/1000) = 0.14 min

Total cycle time = 0.05 + 0.525 + 0.14 = 0.715 min

Production = Volume per cycle x Cycle per hour x E

= 7 x (60/0.715) x 0.83  

= 487.55  LCM/h (approx.)