UNDERCARRIAGE SYSTEMS

UNDERCARRIAGE SYSTEMS

UNDERCARRIAGE IS THE GENERIC TERM GIVEN TO ALL THE COMPONENTS WHICH ARE PART OF THE TRACK DRIVE SYSTEM. THIS TOPIC IDENTIFIES THE VARIOUS TYPES OF TRACK SYSTEMSUSED ON DIFFERENT CATERPILLAR MACHINE MODELS

OVAL TRACK

OVAL UNDERCARRIAGE DESIGN USED TO BE THE STANDARD CONFIGURATION FOR ALL TRACKEDVEHICLES. THE DRIVE SPROCKETS ARE LOCATED AT THE REAR OF THE MACHINE ANDTHE IDLERS ARE LOCATED AT THE FRONT OF THE MACHINE. THERE ARE ONE OR TWO CARRIER ROLLERSAT THE TOP AND A SERIES OF TRACK ROLLERS AT THE BOTTOM SUPPORT THE MACHINE

INTRODUCED ELEVATED SPROCKET TRACK

3CATERPILLAR INTRODUCED ELEVATED SPROCKET TRACK IN THE 1978 TO IMPROVEVARIOUS ASPECTS OF MACHINE PERFORMANCE.

ALL OF THE OTHER MANUFACTURERS OF TRACK TYPEMACHINES USE OVAL TRACK. IN THE CATERPILLAR SYSTEM, ELEVATED SPROCKET IS NOW THESTANDARD FOR ALL SIZES OF TRACK TYPE TRACTORS ALTHOUGH D4

AND D5 SIZE MACHINES AREAVAILABLE WITH OVAL TRACK AS AN OPTION.

TRACK LOADER

CATERPILLAR TRACK LOADERS ARE PRODUCED WITH OVAL TRACK WITH ONE CARRIER ROLLER

SMALL TRACK-TYPE TRACTORS

THE D3C, D4C AND D5C TRACK-TYPE TRACTORS ARE AVAILABLE WITH OVAL TRACK AND ONE CARRIER ROLLER

EXCAVATORS

EXCAVATORS USE OVAL TRACK AND HAVE A RELATIVELY LONG FRAME TO PROVIDE STABILITY FOR THEMACHINE WHILST DIGGING.

MOST HYDRAULIC EXCAVATORS HAVE THREE UNDERCARRIAGE CONFIGURATIONS. THESE ARE STANDARD, EXTENDED AND NARROW AND EACH IS

DESIGNED FOR A SPECIFIC TYPE OFAPPLICATION.

ELEVATED SPROCKET TRACK

TRACK TYPE TRACTORTHE ELEVATED SPROCKET DESIGN IS USED IN MOST CATERPILLAR TRACK-TYPE TRACTORS AND IN

PIPELAYERS.

THE ELEVATED SPROCKET DESIGN ISOLATES THE FINAL DRIVE COMPONENTS FROM SHOCKS WHILE IMPROVING MACHINE BALANCE AND TRACTION AND PROVIDES MAXIMUMFLEXIBILITY FOR MOUNTING TRACK ROLLER FRAMES. THIS RESULTS IN LESS CHANCE OF SEAL DAMAGE.

SUSPENDED UNDERCARRIAGE

LARGER (CATERPILLAR D8 AND UP) ELEVATED SPROCKET MACHINES ARE EQUIPPED WITH ASUSPENDED UNDERCARRIAGE.

THE SUSPENDED UNDERCARRIAGE PROVIDES UP TO15% MORE GROUND CONTACT.THE FOUR MAJOR BOGIES AND THE FOUR MINOR BOGIES CAN OSCILLATE IN THE ROLLER FRAME. THISCAUSES THE TRACK TO BETTER FOLLOW THE

CONTOUR OF THE GROUND.

PIPELAYER

PIPELAYERS ALSO HAVE AN ELEVATED SPROCKET DESIGN (FIGURE 9). THE ROLLER FRAMES INPIPELAYERS DO NOT OSCILLATE RELATIVE TO

ONE ANOTHER.

THIS UNDERCARRIAGE IS DESIGNED TOABSORB IMPACT LOADS AND REDUCE SHOCK LOADS TRANSFERRED TO THE MACHINE.THE ROLLER FRAMES ARE RIGIDLY CONNECTED TO THE MAIN FRAME BY A TWO-POINT MOUNTINGSYSTEM FOR MAXIMUM STABILITY IN PIPELAYING APPLICATIONS.

TRACK SKIDDER

THE TRACK SKIDDER (FIGURE 10) IS EQUIPPED WITH AN ELEVATED SPROCKET THAT IS IN A MOREFORWARD LOCATION THAN THE TRACTORS.

THE POSITION OF THE SPROCKET IS DETERMINED BY BALANCE REQUIREMENTS FOR THE MACHINE. TRACK SKIDDERS ARE USED IN FORESTRYAPPLICATIONS FOR RETRIEVAL OF LOGS BY TOWING OR LIFTING WITH A GRAPPLE.

TRACK FRAME DESIGN - OVAL TRACK

SOME MACHINES USE A RIGID TRACK FRAME DESIGN (FIGURE 11). IN THIS DESIGN THE TRACKFRAME (SIDE FRAME) IS MOUNTED RIGIDLY TO THE MACHINE MAIN FRAME AT THE FRONT, AS WELLAS AT THE REAR.

THERE IS NO RELATIVE MOVEMENT BETWEEN THE TRACK FRAME AND MAINFRAME.THIS FEATURE GIVES THE MACHINE GREATLY IMPROVED STABILITY AND IS

USED ON TRACKEDLOADERS AND EXCAVATORS.

EQUALIZER BAR

THE MAINFRAME CONTAINS A PINNED EQUALISER BAR THAT ROTATES INSIDE A SADDLE.

THE FRONT OF THE ROLLER FRAME IS ATTACHED TO THE ENDS OF THE EQUALISER BAR. THISARRANGEMENT ALLOWS THE ROLLER FRAMES TO OSCILLATE THROUGH A SMALL ANGLE VERTICALLY BUTARE UNABLE TO MOVE LATERALLY.

TRACK ROLLER FRAME PIVOTS

THE FRONT OF THE FRAME IS ALLOWED TOMOVE UP OR DOWN BY THE EQUALISER BAR AT THE FRONT OF THE MACHINE THISARRANGEMENT INCREASES THE STABILITY OF THE MACHINE, AND GIVES EACH TRACK A MAXIMUMGROUND CONTACT AREA.

TRACK ROLLER FRAME PIVOTS AROUND THE REAR AXLE.

TRACK ADJUSTERS

THE TRACK ADJUSTER IS A HYDRAULIC DEVICE. IT IS OPERATED WHEN LUBRICANT ISADDED WITH A HAND GREASE GUN THROUGH A FITTING (2) TO MOVE THE IDLER FORWARD AND TIGHTENTHE TRACK.

TO LOOSEN THE TRACK, LOOSEN THE RELIEF VALVE (1). WHEN THE TRACKS ARE LOOSENEDLUBRICANT WILL COME OUT ONE OR MORE HOLES (3) ON THE SIDES OF THE ADJUSTING ASSEMBLY

RECOIL SPRINGS

THE RECOIL SPRINGS ARE NORMALLY IN COMPRESSION. THEY ARE HELD BETWEENBRACKETS AND STOPS ON THE TRACK ROLLER

FRAMES. NORMALLY, THE RECOIL SPRINGS DO NOT PUSHAGAINST THE TRACK.TRACK

ADJUSTMENT IS MADE BY THE HYDRAULIC MECHANISM FOR TRACK ADJUSTMENT. PRESSURELUBRICANT IS SENT TO A SPACE (3) THROUGH A FILL

VALVE. THIS MOVES THE RECOIL ROD (4) ANDTHE FRONT IDLER FORWARD.

ELEVATED SPROCKET DESIGN

ONE OF THE MOST EASILY SEEN DESIGN CHARACTERISTICS OF THE ELEVATED SPROCKET DESIGN ISTHE TRIANGULAR SHAPE OF THE TRACK.

THE REASON FOR THIS SHAPE IS THAT THESPROCKETS AND FINAL DRIVES ARE ELEVATED (RAISED) ABOVE THE TRACK ROLLER FRAMES. IN THISELEVATED LOCATION, THE FINAL DRIVES ARE INSTALLED ALONG A COMMON CENTRELINE WITH THEBEVEL GEAR AND THE STEERING AND BRAKE CLUTCHES.

DESIGN TRACK TYPE TRACTORS.

THIS DESIGN IS FITTED TO D4 THROUGH D11 TRACK

TYPE TRACTORS.

THE D8 AND ABOVE AREFITTED WITH SUSPENDED UNDERCARRIAGE WHILST THE MODELS BELOW D8 ARE FITTED WITH A RIGIDBOTTOM ROLLER DESIGN.FIGURE 23 SHOWS THE RELATIVE LOCATIONS OF THE MOVABLE COMPONENTS IN THE SUSPENDEDUNDERCARRIAGE ARRANGEMENT.

SEALED AND LUBRICATED CARTRIDGE PIN

A SEALED AND LUBRICATED CARTRIDGE PIN IS SHOWN AT. THERE ARE 16 CARTRIDGEPINS IN EACH ROLLER FRAME (32 PER MACHINE). TWO ARE USED FOR

EACH MAJOR AND MINORBOGIE.

ALL THE CARTRIDGE PINS ARE IDENTICAL. EXCEPT FOR THE RUBBER STOPPERS AND PLASTICPLUGS IN THE ENDS OF THE PIN, NO INDIVIDUAL PARTS ARE SERVICED. IF PIN REPLACEMENT ISNECESSARY, A COMPLETE NEW PIN MUST BE INSTALLED.

CROSS-SECTION

CROSS-SECTION OF SEALED AND LUBRICATED CARTRIDGE PIN THE COMPONENTS AND STRUCTURE OF THE SEALED AND LUBRICATED CARTRIDGE PIN IS SHOWN INTHIS CROSS-SECTION IN.THE COMPONENTS ARE:PININNER COLLAROUTER COLLARBUSHINGRUBBER STOPPERSPLUGSTHRUST RINGS.

RUBBER PADS

THE RUBBER PADS ARE SHOWN IN FIGURE 26. 16 PADS ARE INSTALLED ON EACH MACHINE.FOUR BOLTS HOLD EACH PAD IN POSITION. THE PADS SHOULD BE INSPECTED FOR LARGE CRACKS ORMISSING PIECES OF RUBBER EVERY 500 SERVICE HOURS

ROLLER FRAMES

THE ROLLER FRAMES ARE MADE OF TWO TUBULAR (TUBE SHAPED) STEEL SECTIONS WITH STEELSUPPORT CASTINGS WELDED TO THEM. THIS TUBULAR DESIGN GIVES MAXIMUMSTRENGTH FOR RESISTANCE TO THE

MANY STRESSES CAUSED BY GROUND IMPACT, TOO

FRONT SECTION OF THE ROLLER FRAME

THE TUBE ON THE FRONT SECTION (IN THE AREASHOWN HAS A CHROME PLATED SLEEVE WITH A SMOOTH OUTER SURFACE. A LARGE BRONZEBEARING IN THE FRONT OF THE REAR SECTION IS USED TO SUPPORT THE TUBE IN THE

AREA OF THESLEEVE.

IS A CLOSE VIEW OF THE AREA WHERE THE TUBE ON THE FRONT SECTION OF THE ROLLER FRAME TELESCOPES

INTO THE REAR SECTION.

FRONT SECTION OF THE ROLLER FRAME

TO REMOVE THE FRONT SECTION OF THE ROLLER FRAME, IT IS FIRST NECESSARY TO BREAK (REMOVE) THE TRACK AND INSTALL THE STRAP (FT1552) AS SHOWN IN FIGURE 29. THE STRAP PREVENTSMOVEMENT OF THE MAJOR BOGIE DURING THE REMOVAL AND INSTALLATION PROCEDURE

FRONT SECTION OF THE ROLLER FRAME AFTER REMOVAL FROM THE REAR SECTION.

THE SLOT IN THE OUTER DIAMETER OF THE TUBE IS FOR ONE OF THE TWO KEYS.AT THE RIGHT END OF THE TUBE IS THE CHROME PLATED SLEEVE THAT IS USED AS THE BEARINGAND SEAL SURFACE. AT THE LEFT END OF THE TUBE IS THE TRACK ADJUSTMENT CYLINDER.

SHOWS THE TUBE ON THE FRONT SECTION OF THE ROLLER FRAME AFTER REMOVAL FROM THE REAR SECTION.

THE RECOIL AND TRACK ADJUSTMENT MECHANISM.

DURING RECOIL, THE FRONT ROLLER FRAME ALONG WITH THE PISTON AND THE SPRING SUPPORT MOVE TO THE LEFT (TOWARDTHE REAR OF THE MACHINE). THE CYLINDER CANNOT MOVE BECAUSE IT IS STOPPED AGAINST THEEND OF THE BORE IN THE REAR SECTION OF THE ROLLER FRAME.

SHOWS THE COMPONENTS IN THE RECOIL AND TRACK ADJUSTMENT MECHANISM. THEAREA INSIDE THE CYLINDER AT THE LEFT END OF THE PISTON

IS FILLED WITH OIL.

EQUALIZER BAR

THE RUBBER PADS CONTACT THE BOTTOM OF THE FRAME TO CONTROL THEMOVEMENT OF THE EQUALIZER BAR AND IMPROVE THE STABILITY OF THE MACHINE DURING HILLSIDEOR ROUGH OPERATION. IN THE CENTRE OF THE EQUALIZER BAR IS A SPECIAL NON-METALLIC

BEARINGWHICH DOES NOT NEED LUBRICATION.

THE ROLLER FRAMES ARE CONNECTED NEAR THE FRONT OF THE MACHINE BY AN EQUALIZER BAR. INSTALLED ON TOP OF THE EQUALIZER BAR ARE TWO PAIRS OF WEDGE-SHAPED RUBBER

OSCILLATIONPADS .

MAINTENANCE INTERVAL SCHEDULE

UNDERCARRIAGE SYSTEM