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
TRACK ROLLER FRAME
PIVOTS AROUND THE
REAR AXLE.
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 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
IS A CLOSE VIEW OF THE
AREA WHERE THE TUBE ON
THE FRONT SECTION OF THE
ROLLER FRAME TELESCOPES
INTO THE REAR SECTION.
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.
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.
SHOWS THE TUBE ON THE
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.
THE RECOIL AND TRACK
ADJUSTMENT MECHANISM.
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.
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.
EQUALIZER BAR
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 .
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.
UNDERCARRIAGE SYSTEM
MAINTENANCE INTERVAL SCHEDULE