Hydraulic Shovel Vs Wheel Loader - September 2006.ppt

Hydraulic Shovel Vs. Wheel Loader

Cedric Otzenberger, LFR September, 2006

Why both are such great machines

The Hydraulic Shovel

All pics courtesy of "Le Tourneau"

The Wheel Loader

41 m3

1950's (Liebherr "Elephant")

21st century(Le Tourneau)

The Wheel Loader

The Wheel Loader

1. Generalities

2. Wheel Loader Advantages

3. Hydraulic Shovel Advantages

4. Conclusion

• The Wheel Loader is the best machine to load material

• The Hydraulic Shovel is the best machine to load material

Hydraulic Shovel

WheelLoader

Lousy -

Super -

- Lousy

- Super

Hard Rock Strictly RehandlingHigh Penetration Force Easy Digging

NO travel MUST travelTight Quarters Open Space

High Dumping Height (Lower Dumping Height)Abrasive Material Nonabrasive Material

Rough Floor Smooth Floor

Hydraulic Shovel & Wheel Loader

This is still today where it excels.

This is what the Wheel Loaderoriginally was designed to

Strictly RehandlingEasy Digging

MUST travelOpen Space

(Lower Dumping Height)Nonabrasive MaterialSmooth Floor

The Wheel Loader's basic design has not changed in 55 years

Wheel Loader

Strictly Rehandling

Easy Digging

MUST travel

Open Space

(Lower Dumping Height)

Smooth Material

Smooth Floor

This leads to:

• Large Bucket Capacity

• High Ratio of Bucket capacity to operating weight

• Easy travel and steering (highly maneuverable)

• Rubber tires

• Fast travel speed

• etc.

Wheel Loader

This, by the way, was in 180° contrast to the only loading machine known then - the cable shovel.

These facts made it new, interesting, promising and lent it immediate success.

Wheel Loader

• Large Bucket Capacity

• High Ratio of Bucket capacity to Operating weight

• Easy travel and steering (highly maneuverable)

• Rubber tires

• Fast travel speed

• etc.

1. Generalities



4. Conclusion

"Typical" features of the wheel loader idea:

1- To move the bucket into the material the whole machine has to move

Wheel Loader

• Total weight of machine has to be accelerated from zero to maximum speed FOUR times each cycle

• Total weight of machine has to be braked down from maximum speed to a dead stop THREE times each cycle

• The fourth time the whole machine weight runs into the material tryingto help filling the bucket

To move the bucket into the material the whole machine has to move

The Hydraulic Shovel moves just its Attachment



2- The bucket has to stay at floor level to clear the way for the tires

Wheel Loader

The bucket has to stay at floor level to clear the way for tires

?What, if it's harder material?

The bucket has to stay at floor level to clear the way for tires

The bucket can penetrate anywhere within the attachment digging envelope




3- The bucket HAS to be as wide as the whole machine

Wheel Loader

• This makes buckets relatively wide and spreads penetrating forces thin

• The bucket MUST clear a wide enough path for the tires to avoid damaging them

• If the bucket is not wide enough…….

The bucket HAS to be as wide as the whole machine

(no comment)


• The wheel loader bucket MUST be as wide as the machine.


• The hydraulic shovel can choose the width of its bucket.

The bucket could be as narrow as the attachment

• The hydraulic shovel can penetrate the material from a stand still at any angle.

plus…

The bucket could be as narrow as the attachment

The wheel loader can not !





4- Penetration force depends on the friction value of the rubber tires

Wheel Loader

= Weight of total machine x Tire friction coefficient

Friction coefficient for rubber on dry gravel 0.4 to 0.85wet gravel 0.4 to 0.8dry rock 0.55 to 0.75wet rock 0.55 to 0.75wet ice 0.05 to 0.1dry snow 0.1 to 0.55

(This is why data sheets may show "tractive effort" but not crowd force)

Max. penetration force = friction value of the rubber tires

• When the going gets tough (abrasive), the wheel loader can/will use chains to protect its tires

Note: The friction coefficient of steel on rock is considerably less than the one of rubber on rock, resulting in greatly reduced penetrating force

= Weight of total machine x Tire friction coefficient

Max. penetration force = friction value of the rubber tires



5- Any type shock the bucket lip gets is passed on to the whole machine



4- Penetration force depends on the friction value of the rubber tires

Wheel Loader

Any type shock the bucket lip gets is passed on to the whole machine

This is certainly not the case with the hydraulic shovel

Any type shock the bucket lip gets is passed on to the whole machine

1. Generalities



4. Conclusion

Hard Rock Strictly Rehandling…………………..

High Penetration Force Easy Digging…………………..

NO travel MUST travel…………………..Tight Quarters Open Space…………………..

High Dumping Height (Lower Dumping Height)…………………..

Abrasive Material Nonabrasive Material…………………..

Rough Floor Smooth Floor…………………..

The hydraulic shovel was designed to excel where the wheel loader is weak by design.

The hydraulic shovel

It avoids many of the short comings of the Cable Shovel and . . .

. . . and it does not want to be a replacement for the Wheel Loader

The hydraulic shovel is a loading machine of its own

Hard Rock Strictly Rehandling…………………..






1

234

567

Advantages of the hydraulic shovel over the wheel loader

Hard Rock1

Hard Rock1

Loading hard rock requires:

•High Penetrating or Digging Force

•High Break-out force

REAL*

* "real" meaning - in the material, not just in the data sheet






234

567

High Penetration or Crowd Force2

• Wheel loader: The machine's total penetrating force is as high as its tractive effort, which is limited by the available friction between tires and ground.

= Weight x Tire friction coefficient

• Hydraulic shovel: Its total Crowd force force is determined by its hydraulic cylinders and the attachment geometry. Ground friction is normally not a limiting factor.

Non-moving double grouser shoeswill dig in.

High Penetration or Crowd Force2

This actually available digging force has to be divided by the width of the bucket to get the real or "specific" force per meter of cutting edge

The wheel loader will always have (to have) a wider bucket than the hydraulic shovel

So even with the identical data sheet crowd force/tractive effort, the shovel has a higher specific force = more kN per meter of cutting edge

Cat 994F17 m3

R 935018 m3

5,7m 4,1 m

High Breakout Force2

Breakout force is the available force at the bucket teeth to break the material and fill the bucket once the crowd motion stops.

R 935018 m3

Cat 994F17 m3

F

100

Approx. 0,4 – 0,5m

2

Cat 994F17 m3

Wheel Loader - Breakout Leverage

Per SAE regulation the breakout force for a wheel loader bucket is calculated 100mm (4“) behind its cutting edge.

2

Cat 994F17,5 m3

Wheel Loader - Breakout Leverage

2Wheel Loader - Breakout Leverage

Cat 994F17 m3

Much smallerREAL Breakout Force in the Material

100Calculated Breakout Force per Data sheet

Cylinder force lever

Cylinder force

Breakout force lever lengthused for calculation

Theoretical or Datasheet Breakout force


NEW Cylinder force lever

Cylinder force

Real "In the material" breakout force lever length

REALBreakout forcein the material


In contrast to the wheel loader, per SAE regulation the breakout force for a Hydraulic Shovel bucket is calculated at the tip of the teeth

2Hydraulic Shovel - Breakout Leverage

Cylinder force

Theoretical or Datasheet Breakout force

Cylinder force lever

Theoretical breakout force lever length= Bucket radius

2Hydraulic Shovel - Breakout Leverage

Real "In the material" breakout force lever length

Down pressure of machine and

attachmentREALBreakout forcein the material plus

additional Breakout force from the machine's down pressure

…………………..NO travel …………………..

Tight Quarters

High Dumping Height …………………..

Abrasive Material …………………..

Rough Floor …………………..

4

567

3

MUST travelOpen Space


Wheel Loader - Tight Quarters3

• Loading of trucks with wheel loader requires a lot of room in the loading area

Hydraulic Shovel - Tight Quarters3

• Minimum required space: only for truck positioning / loading and for the

shovel itself

NO travel …………………..




4

567

MUST travel(Lower Dumping Height)Nonabrasive MaterialSmooth Floor

Wheel Loader - NO travel4

• A lot of movement at the face and loading area is required in order to properly position the wheel loader

• This will also lead to effectively and efficiently load haul trucks

Muck pile

Tru

ck

Hydraulic Shovel - NO travel4

• The hydraulic shovel can penetrate the material from a stand still at any angle

• The hydraulic shovel can also load trucks from the same stand still

Muck pile

Tru

ck




567


Cat 994F17 m3

Wheel Loader - High Dumping Height5

• The wheel loader lifting capacity is always lower than the comparable hydraulic shovel model

• Wheel loaders are often equipped with an optional “high lift arrangement” in order to match the existing mine truck fleet

177 tonnes190 tons

• Very short distance to truck

• Danger of truck side damage

• Impossible to pile up the truck

• Bad view

Hydraulic Shovel - High Dumping Height5

• Compared to wheel loaders, hydraulic shovel have several advantages in terms of truck loading situations

• Enough space between the excavator and the truck

• Can easily pile up the truck

• Better view into the truck dump body

R 935018 m3

177 tonnes190 tons

Cat 994F17 m3

Hydraulic Shovel - High Dumping Height5

• Compared to wheel loaders, hydraulic shovel have several advantages in terms of truck loading situations

Max dump height = 7,60m Max dump height = 11,20m

R 935018 m3

177 tonnes190 tons


Rough Floor …………………..67

Nonabrasive MaterialSmooth Floor

Wheel Loader - Abrasive Material6

• Free flowing material

• Very well blasted materials

• Stock piles materials

• Unconsolidated material

The wheel loader is the ideal loading machine for:

Free Flowing

Well Fragmented

Hydraulic Shovel - Abrasive Material6

• Tightly blasted material

• Consolidated Material

Tightly Shot

Consolidated

• Unblasted Material

• Material at the toe of the blast

The hydraulic shovel is the ideal loading machine for:

• In poorly fragmented or abrasive materials, the hydraulic excavator performs better than any other loading tool

• Crowd and breakout forces increase loading efficiency by increasing bucket fill factors

Hydraulic Shovel - Abrasive Material6

Rough Floor …………………..7 Smooth Floor

Wheel Loader - Rough Floor7

• Wheel Loaders used in severe loading applications have shown poor tire life

cycles

• The use of protective chains increases the tire lifetime but decreases the

wheel loader adhesion i.e. penetrating force

Hydraulic Shovel - Rough Floor7

• Hydraulic shovel can work, without restrictions, on varying ground conditions within the pit

1. Generalities



4. Conclusion

Application

• Bad operator’s comfort

• Digging only possible on ground level

• Good cleaning of floor not feasible

• Requires firm ground conditions

• Not suitable for direct digging applications

• Not suitable for drop-ball application

Productivity

• Longer cycles (due to higher number of movements per pass)

• Lower breakout and crowd forces

• Less productive in bad shots

Summary - Disadvantages of Wheel Loaders

Wheel Loader disadvantages = Hydraulic shovel advantages

Capital cost

• Lower life expectancy combined with higher investment at comparable productivity

Operating cost

• Significant cost for tires and protection chains

• Higher power-demand and thus higher fuel consumption for comparable productivity

Wheel Loader disadvantages = Hydraulic shovel advantages

Summary - Disadvantages of Wheel Loaders

Thank you

for your attention

Thank you

for your attention

Documents

Hydraulic Shovel Vs Wheel Loader - September 2006.ppt