Scraper

Scraper

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

ConstructionParts : Bowl, Apron and EjectorBowl: • Loading and carrying component• Has a cutting edge that extends horizontally across front

bottom edge• Lowered for loading, raised during travelApron:• Front wall of the bowl, independent of bowl• Raised during loading and dumping, lowered during haulage –

to avoid spillageEjector:Rear vertical wall, gets activated and moves forward, helps

positive discharge of material

Production Cycle

1. Loading2. Haul travel3. Dumping and Spreading4. Turning5. Return travel6. Turning and positioning to pickup the next

load

Types

Based on method of loading & number of axles1. Pusher Loaded ( Conventional )

a) Single powered axleb) Tandem powered axles

2. Self Loadinga) Push – pull, tandem powered axlesb) Elevating typec) Auger type

Pusher loaded

http://www.youtube.com/watch?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

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

Self loading – Elevating type• Self contained loading &

haulingLoading 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

Auger Type http://www.youtube.com/watch?v=Jq3vXSXFnw8

• Can self load in difficult conditionsEx: Laminated rock, granular materials, frozen

material• Has independent hydrostatic system located at

centre of the bowl• Types – Single and Tandem poweredDis:– Non – load wt is added during haul (wt of mechanism)– More costly to own and operate

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