1. Lecture 6
scrapers
TSP-308 MPK Ferdinand Fassa

2. OUTLINE Introduction Types of Scrapers Scraper Production Chart

3. INTRODUCTION
Excavating, loading, hauling, & dumping over medium distances.
Can be used with pusher tractor for increased production.
Some models have self loading capabilities
Economical over a wide range of haul lengths
Can self load and not dependent on other equipment
Scraper are available with loose heaped capacities up to about 44 cy

4. Types of Scrapers
Push-Loaded: Single Powered Axle

6. Types of Scrapers
Push-Pull: Tandem- Powered Axle

7. Types of Scrapers Auger Scraper
Can self-load in difficult condition (frozen material, lime-stone)
More costly to own and operate than conventional single-or tandem machine

8. Types of Scrapers Elevating is loading and hauling scraper
Used for utility work
Very good in small quantity situation
No pusher required

10. Scraper Production Chart

11. Average Speed Factors
When machinery are required to accelerate and stop in the same section, apply the squared value from column one.

12. Scraper Fixed Time, min

13. Scraper Production Example
Problem
Estimate the production of a single two-axle scraper
Travel time curves are shown on Figures below, Fig. 4-4 & 4-5.
Max Heaped Volume = 31 LCY
Max Payload = 75,000 lb
Material: Sandy Clay, 3200 lb/BCY, 2650 lb/LCY,
Rolling Resistance = 100 lb/ton,
Operating Conditions = Average

16. Scraper Production Example
Haul Route: Section 1. Level Loading Area Section 2. Down a 4% grade, 2000 ft Section 3. Level Dumping Area Section 4. Up a 4% grade, 2000 ft Section 5. Level Turnaround, 600 ft
Turnaround
Load Area
4% grade
Dump Area

17. Scraper Production Example
Loads per Cycle
Heaped Cap. Wt. = 31.0 LCY x 2,650 lb/LCY = 82,150 lbs
82,150 lbs exceeds the 75,000 lbs Rated Max Payload of the Scraper.
The maximum scraper volume is limited by weight to
= 75,000 lbs (Rated Wt)/ 3,200 lb/BCY
= 23.4 BCY/Load

18. Scraper Production Example

19. Scraper Production Example
Travel Time:
Section 2 ~ Down a 4% Grade, 2,000 ft. (1% Eff.)
TT2=1.02 min (Figure 4-4)
Section 4 ~ Up a 4% Grade, 2,000 ft. (9% Eff.)
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft. (5% Eff.)
TT5=0.45 min (Figure 4-5)
TT= = 0.45 = 3.07 min

21. Scraper Production Example
Travel Time:
Section 2 ~ Down a 4% Grade, 2,000 ft. (1% Eff.)
TT2=1.02 min (Figure 4-4)
Section 4 ~ Up a 4% Grade, 2,000 ft. (9% Eff.)
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft. (5% Eff.)
TT5=0.45 min (Figure 4-5)
TT= = 3.07 min

23. Scraper Production Example
Travel Time:
Section 2 ~ Down a 4% Grade, 2,000 ft.
TT2=1.02 min (Figure 4-4)
Section 4 ~ Up a 4% Grade, 2,000 ft.
TT4=1.60 min (Figure 4-5)
Section 5 ~ Level Turnaround, 600 ft.
TT5=0.45 min (Figure 4-5)
TT= = 0.45 = 3.07 min

24. Scraper Production Example
Fixed Cycle (Table 4-7) – Average Conditions – Single Engine
Spot = 0.3 min.
Load = 0.6 min.
Maneuver & Dump = 0.7 min.
Total Fixed Time = = 1.6 min
Total Cycle Time = = 4.67 min.
Estimate Production = 23.4BCY/Load x [(50min/h)/(4.67min/Load)] = 251 BCY/h

25. Scraper Fixed Time, min

26. Scraper Production Example
Fixed Cycle (Table 4-7)
Load Spot = 0.3 min.
Load = 0.6 min.
Maneuver & Dump = 0.7 min.
Total Fixed Time = = 1.6 min
Total Cycle Time = = 4.67 min.
Estimate Production = 23.4BCY/Load x [(50min/h)/(4.67min/Load)] = 251 BCY/h

27. Push-Loading

30. Typical Pusher Cycle Time, min

31. Number of Scrapers Served, Pushers Required & Production
(# of scrapers that can be handled by one pusher w/o scraper delay)
(# of pushers required to service a fleet of scrapers: round up to next integer)

32. Scraper Push-Loading Example
Problem The estimated cycle time for a wheeled scraper is 6.5 min. Calculate the number of pushers required to serve a fleet of nine scrapers using pushers. Determine the result for both backtrack and chain loading methods.

33. Scraper Push-Loading Example
Cycle Times from Table 4-8

34. Optimal Load Time

35. Optimum Load Time

36. Cycle Time minus Load Time = 3.0 min.

37. CONSTRUCTION EQUIPMENT AND METHODS
Next Week:
Lecture 7
CONSTRUCTION EQUIPMENT AND METHODS