1. Estimate the cycle time and production of a Caterpillar 777D flat floor off highway truck operating on a level haul road of 4000m length. The road is a rutted dirt roadway with no maintenance and no stabilisation, tyre penetration is 2.5 cm. The following can be assumed;
- Loading time 1.4 min
- Manoeuvre and dump time 0.8 min
- Truck hauls 80 tonnes of ore each trip
- Job efficiency of 0.8
2. For the situation in question 1, determine the cycle time if road conditions were improved to a rolling resistance of 20 kg/tonne.
3. For the problem in question 1 and 2 the engineer at the site is considering the use of a shorter, 2,200m, haul road that has a slope of 6% adverse. If all other factors remain the same which haul route should be selected on the basis of shortest cycle times? What are the cycle times and hourly productions?
4. An off highway truck weighs 23 t empty and carts a payload of 35 t up a 4% grade. The RR factor is 40 kg/tonne. Calculate:
a) The total resistance (kg)
b) The effective grade (%)
5. A rubber tyred scraper unit weighing 50 t is towed by a crawler tractor weighing 40t up a 6% grade. The RR factor is 40kg/t. Calculate:
a) The rolling resistance (kg)
b) The grade resistance (kg)
c) The total resistance (kg)
6. A Caterpillar D3OD articulated dump truck has the rim pull curve in the figure below. (Gross weight 21.9 t empty, 49.117 t loaded). If the truck ascends a 5% grade with a rolling resistance of 40kg/t, find the following:
a) Total resistance (kg)
b) The required rim pull (kg) when loaded
c) The maximum speed of the truck when loaded (km/h)
7. The average speed of an 18m3 scraper is 37 km/hr and its return speed uphill is 16 km/hr over a 1000 m haul distance and a 1000m return distance. Using a fixed time of 4 minutes, calculate the cycle time (min).
8. What are the advantages and disadvantages of in-pit crushing