As a project manager of Very Good Construction you want to plan renting a fleet of 25 cu yd tractor-scrapers and have them hauling between the pit and a road construction job. The haul road is a rutted dirt road that deflects slightly under the load of the scraper. There is a slight grade of 2.5% from the pit to the fill location. Rolling resistance factor is assumed as 100 lbs/ton. The return road is effectively level. The haul distance to the dump location is 0.50 miles and the return distance is 1.50 miles. The scrapers are push loaded in the pit. The cycle time for the pusher is 1.50 minutes and the cycle time for the scrapers is 8 minutes. Assume that the weight on the wheels is 75 tons (full) and 50 tons.1. What are the rolling resistances and grade resistance?
2. What are the effective grades?
3. How many scrapers you recommend to be rented? Explain.
4. What is the production of the system in case 4 scrapers would be rented?