CHAPTER
9
Scrapers
Resisting Force (loaded) = [(55 𝑙𝑏.
𝑡𝑜𝑛)(45.9 𝑡𝑜𝑛)] – [(2% ) (20 𝑙𝑏.
𝑡𝑜𝑛
Resisting Force (empty) = [(55 𝑙𝑏.
𝑡𝑜𝑛
From Figure 9.10: Speed (loaded) = 29 mph; Speed (empty) = 28 mph
Distance Max. Speed Speed Factor Speed Time
2,640 ft. 29 mph 0.88 25.5 mph 1.18 min.
2,640 ft. 28 mph 0.88 24.6 mph 1.22 min.
(Speed factors were determined from Table 9.2 by linear interpolation between 0.86 and 0.92
to estimate speed factors for 1,320 feet.)
For favorable conditions, the fixed time from Table 9.1 is 1.1 min.
(3.5 𝑚𝑖𝑛.)(1.25 𝐿𝐶𝑌
𝐵𝐶𝑌)=165 𝐶𝐶𝑌
9 – 2
Contractor needs to use 2 scrapers.
2.
𝐵𝐶𝐹)(27𝑐𝑢.𝑓𝑡.
𝑐𝑢.𝑦𝑑.)(1.1)
Since this exceeds the maximum allowable weight, the maximum volume is weight constrained.
Distance Max. Speed Speed Factor Speed Time
For average conditions, the fixed time from Table 9.1 is 0.7 min. + 0.3 min + 0.5 min or 1.5
9 – 3
min.
𝐶𝑦𝑐𝑙𝑒 𝑇𝑖𝑚𝑒 = 1.5 𝑚𝑖𝑛.+ 9.47 𝑚𝑖𝑛.+ 2.87 𝑚𝑖𝑛.= 13.84 𝑚𝑖𝑛.
2. (continued)
ℎ𝑟. )
3. a.
𝐵𝐶𝑌)(1.1)
Since this exceeds the maximum allowable weight, the maximum volume is weight constrained.
9 – 4
3. a. (continued)
Distance Max. Speed Speed Factor Speed Time
3,000 ft. 22 mph 0.89 19.6 mph 1.74 min.
3,000 ft. 24 mph 0.89 21.4 mph 1.59 min.
(Speed factors were determined from Table 9.2 by linear interpolation between 0.86 and 0.92
to estimate speed factors for 1,500 feet.)
For average conditions, the fixed time from Table 9.1 is 0.7 min. + 0.3 min + 0.5 min or 1.5
Contractor needs to use 4 scrapers.
3. b. (Fleet productivity determined by productivity of the pusher.)
3. c.
9 – 5
⁄)
⁄)=$𝟏.𝟓𝟓
4. a.
𝐵𝐶𝑌)(0.85)
From Figure 9.11: Speed (loaded) = 6 mph; Speed (empty) = 16 mph
Distance Max. Speed Speed Factor Speed Time
3,000 ft. 6 mph 0.89 5.3 mph 6.43 min.
3,000 ft. 16 mph 0.89 14.2 mph 2.40 min.
(Speed factors were determined from Table 9.2 by linear interpolation between 0.86 and 0.92
to estimate speed factors for 1,500 feet.)
9 – 6
Contractor needs to use 6 scrapers.
4. b.
𝐵𝐶𝑌)(1.1)
From Figure 9.11: Speed (loaded) = 6 mph; Speed (empty) = 16 mph
Distance Max. Speed Speed Factor Speed Time
3,000 ft. 6 mph 0.89 5.3 mph 6.43 min.
3,000 ft. 16 mph 0.89 14.2 mph 2.40 min.
(Speed factors were determined from Table 9.2 by linear interpolation between 0.86 and 0.92
to estimate speed factors for 1,500 feet.)
For favorable conditions, the fixed time from Table 9.1 is 0.5 min. + 0.2 min + 0.3 min or 1.0
min.
9 – 7
ℎ𝑟. )
From Figure 9.11: Speed (loaded) = 16 mph; Speed (empty) = 33 mph
Distance Max. Speed Speed Factor Speed Time
3,000 ft. 16 mph 0.89 14.2 mph 2.40 min.
3,000 ft. 33 mph 0.89 29.4 mph 1.16 min.
9 – 8
(Speed factors were determined from Table 9.2 by linear interpolation between 0.86 and 0.92
to estimate speed factors for 1,500 feet.)
For favorable conditions, the fixed time from Table 9.1 is 0.5 min. + 0.2 min + 0.3 min or 1.0
min.
4. c. (continued)
5. a.
𝐵𝐶𝑌)(1.1)(0.95)
9 – 9
Distance Max. Speed Speed Factor Speed Time
5,280 ft. 11 mph 0.93 10.2 mph 5.88 min.
5,280 ft. 28 mph 0.93 26.0 mph 2.31 min.
5. a. (continued)
(Speed factors were determined from Table 9.2 by linear interpolation between 0.92 and 0.94
to estimate speed factors for 2,640 feet.)
For unfavorable conditions, the fixed time from Table 9.1 is 1.0 min. + 0.5 min + 1.0 min or
2.5 min.
5. c. 𝑆𝑐𝑟𝑎𝑝𝑒𝑟 𝐶𝑜𝑠𝑡=$196
9 – 10
⁄)
⁄)=$𝟑.𝟖𝟎
Which is less than the rated maximum load of 75,000 pounds.
Thus the 𝐿𝑜𝑎𝑑 𝑉𝑜𝑙𝑢𝑚𝑒=(31 𝐿𝐶𝑌)(1.1)=𝟑𝟒.𝟏 𝑳𝑪𝒀
6. b. 𝐿𝑜𝑎𝑑𝑒𝑑 𝑊𝑒𝑖𝑔ℎ𝑡=96,880 𝑙𝑏.+ 71,694 𝑙𝑏.=168,574 𝑙𝑏.
6. c.
6. d.
Distance Max. Speed Speed Factor Speed Time
5,000 ft. 26 mph 0.93 24.1 mph 2.35 min.
9 – 11
5,000 ft. 13 mph 0.93 12.1 mph 4.70 min.
(Speed factors were determined from Table 9.2 by linear interpolation between 0.92 and 0.94
to estimate speed factors for 2,640 feet.)
6. d. (continued)
For unfavorable conditions, the fixed time from Table 9.1 is 1.0 min. + 0.5 min + 1.0 min or 2.5
min.
6. e. 𝑃𝑢𝑠ℎ𝑒𝑟 𝐶𝑦𝑐𝑙𝑒 𝑇𝑖𝑚𝑒 =[(1.4)(1.0 𝑚𝑖𝑛.)] + 0.25 𝑚𝑖𝑛. = 1.65 𝑚𝑖𝑛.
Therefore, the productivity of the pusher governs.
ℎ𝑟. )(0.88 𝐶𝐶𝑌
𝐵𝐶𝑌)
