This document discusses tractor pulled scrapers, which are versatile machines used to load, haul, and dump loose materials like soil over a range of haul distances. Scrapers have three main parts - a bowl for loading and carrying material, an apron on the front of the bowl, and an ejector in the rear. They follow a production cycle of loading, hauling, dumping, turning, and returning to load again. Scrapers are classified based on their loading method as pusher loaded, self-loading push-pull, elevating, or auger types. Pusher loaded scrapers rely on other equipment to load them while self-loading types can load independently. Scrapers are rated based on their struck

1. Scraper

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

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

11. Pusher loaded
http://www.youtube.com/w
atch?v=isSp7a2x-r8
• High speeds on favorable
haul roads
• 35 mph (50 km/hr) when
fully loaded
• Lack of high tractive effort
reqd for loading
• Necessary to supplement
with help loading

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