2. Introduction
• Tractor pulled scrapers: Designed to load, haul
and dump loose material in controlled lifts
• High versatility
– Used to load and haul a wide variety of materials
– Economical over wide range of haul lengths and haul
conditions
– Self loading – not dependent on other equipment
– Not as efficient as exclusively designed machines
– Off highway and <1 mile scraper is better than trucks
– Ability to deposit loads in layers of uniform thickness
3. Construction
Parts : Bowl, Apron and Ejector
Bowl:
• Loading and carrying component
• Has a cutting edge that extends horizontally across front
bottom edge
• Lowered for loading, raised during travel
Apron:
• Front wall of the bowl, independent of bowl
• Raised during loading and dumping, lowered during
haulage – to avoid spillage
Ejector:
Rear vertical wall, gets activated and moves forward, helps
positive discharge of material
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9. Production Cycle
1. Loading
2. Haul travel
3. Dumping and Spreading
4. Turning
5. Return travel
6. Turning and positioning to pickup the next
load
10. Types
Based on method of loading & number of axles
1. Pusher Loaded ( Conventional )
a) Single powered axle
b) Tandem powered axles
2. Self Loading
a) Push – pull, tandem powered axles
b) Elevating type
c) Auger type
12. Self loading - Push – pull type
http://www.youtube.com/watch?v=tLR7LZh3VM0
• Tandem powered axle scrappers having a cushioned
push block & bail mounted at front
• A hook on the rear above the usual back push block
• These features enable one another during loading
• Trailing scrapper pushes the lead scrapper as it loads
• lead scrapper pulls the lead scrapper to assist in loading
• Each can individually work with a pusher
13. Self loading – Elevating type
• Self contained loading &
hauling
Loading mechanism: Chain
mounted elevator – mounted
vertically on front of bowl
Disadvantages: Weight of
elevator assembly – dead wt
during haul cycle
Applications:
utility work, dressing up behind
high production
spreads, shifting material
during high grading
operations
14. Auger Type
http://www.youtube.com/watch?v=Jq3vXSXFnw8
• Can self load in difficult conditions
Ex: Laminated rock, granular materials, frozen
material
• Has independent hydrostatic system located
at centre of the bowl
• Types – Single and Tandem powered
Dis:
– Non – load wt is added during haul (wt of mechanism)
– More costly to own and operate
15. Volume of Scraper
• Struck or Heaped capacity
of the bowl (Cubic yard)
Struck capacity: Volume that
a scraper would hold if
the top of the material
was struck off even at the
top of the bowl
Heaped capacity: struck
capacity plus a heaped
load at a 2:1 angle on top
up to a point in the centre
(1/3 more than struck)
SAE – 1:1
