Types of Loaders ©Dr. B. C. Paul 2000

Loading Equipment l Four Basic Types of Loaders Cable Shovel Hydraulic Front Shovel (also called hydraulic excavator) Backhoe Front End Loader

F is the Bucket - note that it is a solid unit. Dumping is achieved by rotation. Can be critical consideration in loading height G is Teeth - FELs known as 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 hinges and hydraulics used for rotating the bucket - They provide limited pry and dig motion C is a one piece arm moved by hydraulic cylinder D - Wide bucket - Rigid Arm - Limited Pry Pivot on bucket Limited Digger

Crowd Motion on an FEL Crowd Motion is the Tires. The machine drives forward - Powered by Diesel Engine A Problem of Tearing up Underfoot under wet conditions Hydraulics on arm competes with propel motion for power Oh Cool It has a Counter- Weight to help with Digging Force

The Articulated Machine Front End Loaders are articulated which gives them their Y shape loading pattern Mobility of FEL makes great for cleaning up spills

The Dilemma of Cab Position l Which side of the articulation point does the cab go on? l 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 l 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 dump bucket - 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 for gentle loading - can position low over truck and open bucket at a controlled rate

The Machine That Digs It Machine has two piece are and a pivoting bucket - Allows range of motion like human arm - lots of dig and pry for hard rock Can Selectively Pick Out Rock Layers - Can be valuable for acid or toxic layers or prep. of synthetic topsoil Hydraulics can develop 100,000 psi at the teeth

The Machine That Swings This is a track mounted machine lacks mobility of FEL - Picks up load and pivots to dump into truck Tracks provide for low bearing pressure. Coupled with minimal movement is much easier on ground - especially when wet

View Arrangements Cab Location Provides Good View of Digging Operation Cab Location to one side can be a view problem for loading a truck on the wrong side Has a Low Built Upper Structure to allow open top access to components - with 5000 psi on hoses you need it

Other Machine Properties l Power Supply Can be Diesel or Electric (often Diesel) l Power is converted to hydraulic for most motions including propel Hydraulics allow trade off between power and speed at steady engine speed l Very Gradable - Can Pull itself up with boom

The Backhoe

The Cable Shovel Basic Design has changed litte from the turn of the 1900s Spindly version shown here is stripping shovel. Was never popular outside Midwest and none built since 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 Almost anything with no loading height problem Has Cables rather than hydraulics to drive motions - 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 hydraulic excavator - big inertia and slower moving Has same operator cab view problem as HE Has a full field shop on back

Cable Digging Technique Has the limited swing up digging problem of the FEL Dipper (not called a bucket on this machine) does not pivot Cable connections avoid major shock transfers to boom - lets outlive the HE Crowd produced by either rack and pinion on boom or cable wheels - wheels preserve insulating boom from shock

Powering Cable Shovels l Except for Mike Muligan’s Steam Shovel all the big ones are electric l Extension Cord Does Limit Mobility (one reasons for machine shop on back) l New SCR and Frequency Control Systems offer good power control - even giant circuit boards Simplicity makes high reliability

Comparative Advantages of Each