You own a fleet of 30-cubic-yard tractor scrapers and have them hauling between the pit and a road construction job. The haul road is clayey and deflects slightly under the load of the scraper. There is a slight grade (3%) from pit at the fill location. The return road is level. The haul distance to the dump location is 0.5 miles and the return distance is 0.67 miles. Four scrapers are being used.

a. What is the rimpull required when the scraper is full and on the haul to the fill?

b. What are the travel times to and from the dump location (see Figure 15.10)?

c. The scrapers are push-loaded in the pit. The load time is 0.6 minutes. What is the cycle time of the pusher dozer?

d. Is the system working at, above, or below the balance point? Explain.

e. What is the production of the system?

Figure 15.10

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Travel time (one-way) -minutes Travel time (one-way) - minutes 50 5 d 2 N 1.2 T 1.0 3 0.4 0.2 0.8 0.6 1.2 1.0 4- 0.8 0.6 3 0.4 0.2 0 100 300 400 500 Feet 150 Meters 200 Vehicle empty weight: 75,800 lb (34,400 kg) 100 15% 300 400 500 Feet 150 Meters 10% 8% 200 4% 0% 1,000 15% 10%- 6% -0%- 400 1,000 1 400 Travel time curve-loaded 15% 2,000 600 800 Travel distance (one-way) Loaded 3,000 Travel time curve-empty Vehicle empty weight: 75,800 lb (34,400 kg) 1,000 1 2,000 600 800 Travel distance (one-way). 3,000 10% 11 1,000 1 8% HT 4,000 1,200 15% Payload 72,000 lb-bank cu yd (32,700 kg-bank cu yd) 4,000 1,200 !1 Empty 1 il H 11 6% 5,000 1,400 Meters T 2% 0% 1. L Feet 10% 8% 6% 4% a al TO 0% Effective grade Feet 5,000 1,400 Meters Effective grade