Types of Loaders

©Dr. B. C. Paul 2000Modified 2009

Note – These slides contain drawings copied from the bookSurface Mining Equipment

Loading Equipment

Four Basic Types of Loaders• Cable Shovel• Hydraulic Front Shovel (also called

hydraulic excavator)• Backhoe• Front End Loader

Front End Loader

F is the Bucket - note that it is a solid unit.Dumping is achieved byrotation. Can be criticalconsideration in loadingheight

G is Teeth - FELs knownas whimpy diggers - load is spread over a bucket as wide as a machine - May have penetrating V

Digging Motion of FEL

I, J, H, and E are the hingesand hydraulics used for rotating the bucket - They provide limited pry and dig motionC is a one piece arm movedby hydraulic cylinder D - Wide bucket - Rigid Arm - Limited Pry Pivot on bucketLimited Digger

Crowd Motion on an FEL

Crowd Motion is the Tires.The machine drivesforward - Powered by Diesel Engine A

Problem of Tearing upUnderfoot under wetconditions

Hydraulics on armcompetes with propelmotion for power

Oh CoolIt has aCounter-Weight tohelp withDiggingForce

The Articulated Machine

Front End Loaders arearticulated which givesthem their Y shape loadingpattern

Mobility of FEL makesgreat for cleaning upspills

The Dilemma of Cab Position

Which side of the articulation point does the cab go on?

Put it in Front• Driver has better view of digging• He is in a better position to get

squished if the pile collapses• Very bad backing view - this machine

moves fast

The Other Choice

Put the Cab on the Back• Still a reasonable Dig view with less

opportunity to get squished• Still rather marginal on backing view -

some things are just dangerous• Vibration from motor causes operator

fatigue• Now putting cabs on flotation

suspensions

Hydraulic Front Shovel

Has a two piece bottom dumpbucket - Higher wear from two pieces

- Bottom open eliminates need to pivot to dump - helps loading height - Can get a rock stuck too

Hydraulic bucket opening forgentle loading - can position low over truck and open bucket at a controlled rate

The Machine That Digs It

Machine has two piece areand a pivoting bucket - Allows range of motion like human arm - lots of dig and pry for hard rock

Can Selectively Pick OutRock Layers - Can be valuable for acid or toxic layers or prep. of synthetic topsoilHydraulics can develop100,000 psi at the teeth

The Machine That Swings

This is a track mounted machinelacks mobility of FEL - Picks up load and pivots to dump into truck Tracks provide for low bearingpressure. Coupled with minimalmovement is much easier onground - especially when wet

View Arrangements

Cab Location Provides GoodView of Digging Operation

Cab Location to one sidecan be a view problem forloading a truck on the wrongside

Has a Low Built UpperStructure to allow open topaccess to components - with5000 psi on hoses you need it

Other Machine Properties

Power Supply Can be Diesel or Electric (often Diesel)

Power is converted to hydraulic for most motions including propel• Hydraulics allow trade off between power

and speed at steady engine speed

Very Gradable - Can Pull itself up with boom

The Backhoe

The Cable Shovel

Basic Design has changed littefrom the turn of the 1900sSpindly version shown here isstripping shovel. Was neverpopular outside Midwest andnone built since 1969 - had more limited overburden range than dragline - operates on pit bottom so more vulnerable to water - had lower profit margin than draglines.

The Mining and Quarry Version

Tall Massive Machine So Can Load Almostanything with no loading height problem

Has Cables rather than hydraulics to drivemotions - Can move in tension but gravity needed for other motions - dipper door is tripped and swings open under gravity

Is a track and pivot machine like hydraulicexcavator - big inertia and slower movingHas same operator cab view problem as HEHas a full field shop on back

Cable Digging Technique

Has the limited swing up diggingproblem of the FEL

Dipper (not called a bucket on thismachine) does not pivot

Cable connections avoid major shocktransfers to boom - lets outlive the HE

Crowd produced by either rack andpinion on boom or cable wheels - wheels preserve insulating boom from shock

Powering Cable Shovels

Except for Mike Muligan’s Steam Shovel all the big ones are electric

Extension Cord Does Limit Mobility (one reasons for machine shop on back)

New SCR and Frequency Control Systems offer good power control - even giant circuit boards• Simplicity makes high reliability

Comparative Advantages of Each

Loaders We Are Offered to Consider

The following loaders are also to be considered Cat 994F with a 24.5 yard bucket Cat 988BLog with a 38.66 yard bucket Cat 5230B with a 22.5 yard bucket Cat 5230ME with a 21 yard rock bucket Cat 345B L series 2 with a 3.3 yard bucket P+H 2300XPA with a 27 yard dipper P+H 4100 with a 56 yard dipper

What Must a Good Loader Do?

It has to be able to handle the material without tipping over

It has to be able to get the load over the edge of the truck and preferably center and heap the truck

It has to be able to fill the truck in a reasonable integer number of passes

It has to be able to maneuver on the ground conditions and space available in the loading configuration

My Decisions

I propose to disqualify all front end loaders• Trucks at the bottom of the 3rd bench will

get stuck so the FELs will almost surely get stuck also

• FEL also has no chance of lifting high enough to load a truck on the top of a 30 foot bench.

Actually anything that loads from the bottom of the bench will be down in the mud• I’m going to suggest a Back Hoe