Hydraulic II


  • Store fluid (9x of cap)
  • Cool fluid
  • Settle sediment
  • Outlet, Return, and screen mesh
  • Non-pressurized
    • Safer, cheaper, ease of expansion (oil)
    • Placement (has to be above the pump), easier to get contaminated, lower boiling point, suck air
    • 14.7 psi applied on fluid
  • Pressurized (Opposite with non-pressurized)

Hydraulic fluid

  • Viscosity
  • Oil resistance to flow
  • Affected by temperature
  • Cleaning properties
  • Anti-foaming
  • Demulsification (water)
  • Oxidization (fluidbs too hot -> oxidize)
  • Corrosion protection
  • Petroleum $ - best for lub
  • Anti-flammable $$ - used in mining
  • Biodegradable $$$ - environmental concerns


  • bCreate flowb
  • Inlet line
  • Low pressure, bigger line compared to pump outlet to prevent cavitation.
  • Can use cheaper pump before expensive pump to protect the expensive one from cavitation
  • Non-positive - centrifugal (water pump)
  • Positive - what go in must come out!
  • System relief valve
  • Protect the pump
  • Sense upstream of the valve (inlet side)
  • Pick something heavy, valve on
  • Adjust valve, try low idle first, then increase
  • Mechanical efficiency is the amount of power required to overcome the internal friction (95% mechanically efficient, 5% wasted to overcome pump friction)
  • “Flow is speed” & resistance to flow is pressure
  • Vary input speed change vol of a fixed displacement pump. (Therebs a max revolution per minute on the pump)


  • Positive displacement
  • 80 - 85%
  • Unbalanced
  • Tolerance to contamination
  • $
  • 1500 ~ 4000 psi
  • Oil pump on ICE, charge pump
  • no way to compensate for wearing
  • low pressure in inlet side, causing cavitation in outlet side


  • Positive displacement
  • 85 - 80%
  • Fixed or variable
  • Balance or unbalanced
  • Stricter contamination
  • $$
  • ~3000 psi
  • power steering on road
  • automatically compensate wear as vanes always force out


  • Positive displacement
  • 90 - 95%
  • Fixed or variable
  • Balanced
  • Small clearance, susceptible to contamination
  • $$$
  • ~5000psi
  • main hydraulic, air conditioning
  • always odd # piston, otherwise 2 pistons can be canceled each other in and out @ the same time
  • wash plate never go to zero (3 degree for lub)

Quiz review

  • Velocity is speed expressed as feet per second or meters per second
  • Power is the amount of work done in a specific time.
  • Hydrostatic - high pressure low flow - hydraulic systems
  • Hydrodynamics - low pressure, high flow - torque converter

Lab: hydraulic jack

  • Components
    • Oil
    • Check valves
    • Relief valve (the handle)
    • Actuator
    • Hand Pump
  • How much it can lift ?
    • Hand pump: Stroke 5b, Area: 1 in2
    • Piston: Stroke 12 in, Dia 8 in
    • Hand pump ratio: 3:1 bend at 200 lbs; Can lift: 30,159 lb 1591
  • Increase dia of actuator to increase lift cap.
  • A hole on threaded top cylinder Limit max travel, oil go back to the tank.
  • A hole on thread rod nut - Jack up, air escape, jack down, air in

  • Cylinder drift -> slowly go down because of leakage
  • As long as the leak does not overdo the pump, actuators still do the work, but slow

Lab: Tyrone gear pump

  • Vane pump Intra vane always have outlet pressure acting on space below intra vane. If we have passageway, we need to flip the rotor when we want to change direction of the pump. Spring for initial start of a motor as we donbt have centrifugal force at the beginning.

Eccentric pump (internal gear) -> great torque ump - pressure limiting Bia spring wants full flow

Back off system relief before starting run the new installed pump! Especially when the old pump is broken badly, and we donbt know reason.


Pressure intensification Drift Single acting cylinder: (rely on other force such as gravity or springs to move in the opposite direction) Double acting (single rod cyl = differential cyl) Double acting non-differential (power steering) Single acting Telescoping cyl

Piston relief Cylinder cushion - reduce speed of cyl upon reaching the end Cushion plunger Return drilling

Anti Cavitation Circuit relief

Cylinder Cushion, metering out Cylinder relief valve Hole in cylinder barrel Flow test bInline testb with the pump, good to determine condition of the pump System relief valve : 3000 psi Flow meter: 2500 psi Check flow rate on flow meter show 10GPM compared to pump rated 20 GPM => pump is less than 50% => pumpbs done bTee testb Death end the function (Rod touch bottom) => flow meter show full load reading, and we can check cracking pressure of system relief valve. Vane motor Converting oil flow and pressure into speed and force To increase speed of motor: Use bigger pump Use smaller motor Small gear drive big gear => gear reduction => multiply torque Drain plug on motor cause back pressure

Ttest internal leakage of motor Plug out put to tank Send oil flow to the motor Take 5 Gal container to hold flow coming from the drain port. Result: PRessure relief valve open -> pump OK Fill up the container quickly before relief valve open -> pump NOK

Test internal leakage of cylinder Plug return line Send oil flow to rod end Result: Pressure intensify, no movement = > cyl OK Piston go up! => cyl pump NOK (too much internal leakage, cyl valve leaks, wear seal). bValve = Controlb Pressure Controls Flow controls Directional Control

Piston - Lab Pitting on cylinder bores, pistons, rods shows cavitation by doing finger nail test Leaking may happens on piston rod end seals because of cavitation of the rods. New seal on piston end is just a lip type seal, easy and quick to replace Old packing contains lots of seals; fixing cost more effort; need remove to whole piston to fix the leak seal. Big leak -> slow; not lift any more, everything spits on the ground. Chrome exposed on environment every time extend, weakness! Piston relief relieves some pressure upon it reach the ends, to slow piston down & reduce torque that may damage dead ends. Quick drop valve - Lab Quickly drop/extend piston by pumping oil from rod end to base end (increasing flow rate of pump by using flow rate from rod end) Power down: Accumulator Store hydraulic energy Smooth out operation Maintain pressure, do not need to run the pump all the time. Without accumulator: heat, fuel, and wear increase as everything underload

Pressure relief Main Relief Circuit Relief Unloader valve Externally drained Replace circuit relief valve Pressure Reducing valve Internally drained Sequence valve Normally closed Sense upstream of the valve Drain was blocked, then valve is not opened Counterbalance Internally drained Brake Valve Prevent the load from overspeeding the motor Provide a controlled deceleration of the load Sense upstream and downstream of the motor Lock Valve Hold a suspended load in the event of a hydraulic line rupture Prevent drifting Prevent load overspeeding the actuator

Pressure Compensated flow control valve Orifice creates pressure difference. Q = A * P (Flow is related to the Area of orifice & the Pressure drop across that orifice.) The orifice is automatically adjusted to achieve bInlet Pressure = Spring + outlet pressure) Bypass type, oil flow back to reservoir; restrict type, restrict inlet (need pressure comp pump) Flow dividers Priority flow (steering system) Proportional flow

Lab review Extra plugs on the device assist manufacture process only (creating passageway) EF : excess flow CF : control flow Orifice does not control flow; to control flow, oil should direct to tank, or pump must be de-washed

Exam 1 review

  1. Strainer size by mesh (number of boxes on 1 square inch),
  2. drive shaft end determine rotation of the vane pump 14 Positive displacement pump maintains relatively constant volume regardless of resistant to flow
  3. Pressure pike cause cracking of pump component, drive shaft shear of, seal leakage.
  4. Scoring of the pistons in a piston motor would cause lower motor speed, just like engine, oil go back to tank-> less oil flow -> reduce speed. 39 Flow is speed, not pressure or force
  5. Protect filter when starting with cold oil, (by pass valve in oil filter) (prevent blowing filter)

Restrictor typebs Springbs broken -> press diff decrease

  1. Sequence valve is external drained (IM RIGHT HERE, just for ref)

Compare hydraulic & electrical

  • Hydraulic: pump create flow, load determine pressure
  • Electrical: battery create voltage, load determine current flow

Directional Control Valves

  • Positions / how is it centered
  • How many ports/ways: NO/NC, motor spool, float, P.B. (power beyond)
    • Float work well with round contour
  • How it’s actuated
    • Proportioning (solenoid) Electronic controls pilot circuit, running at constant psi
    • Discrete solenoid: on/off
    • Air (on/off)
    • Hydraulic
    • Wheels
    • Mechanical
  • Detents -create void at rod end if shock load


Hydraulic systems

Open Center hydraulic systems (constant flow system)

  • Cheap
  • has unrestricted path to tank
  • Least efficient, powered can be wasted in form of heat
  • Used on haul truck as the system is not operated during a high % of duty cycle
  • Fixed displacement pump, vary speed of engine causing vary speed of the pump
  • Waste 7HP in neutral

Constant horse power - open center

  • Destroke pump when pressure rises to limit the maximum power that the pumps can draw from the engine
  • Applications: Excavator, faster speed @ lighter load, lower speed @ heavier load
  • If the pump is not destroke, the engine would stall for its limit capacity

Pressure compensation

  • Ability to lower flow as output pressure increase
  • Bias spring wants full flow
  • Waste 1.75HP in neutral

Closed center system (demand flow system)

  • Maintain maximum system pressure available to perform work by accumulator
  • Waste 7HP in neutral

Load sense (closed center)

  • Waste 0.14HP in neutral

Open loop circuit: returned oil from actuators flow back to tank Closed loop circuit/HST: returned oil from actuators flow back to pump inlet

Cat 246

  • Hydrostatic test
    • 4 quad gauges
    • Laptop
    • up on stands, tires rotating

Cat 315: Big excavator (constant horse power)

  • The boom / stick and bucket will NOT move

Close flowmeter a little bit to warm things up

JD 344: loader

  • T test, have parallel path to tank, may close orifice off, oil are lazy, it will go to tank

    Cat 277 Skid steer loader (Multi terrain loader)

  • Test loader function
  • Can move
  • Laptop, flowmeter on auxiliry port
  • Series test
  • use transducer

    Cat 305D: little excavator

focus on the boom

Some names of equipment

  • dozer
  • crawler tractor
  • excavator
  • wheel loader
  • skid steer loader

Exam 2 review

  • swivel joint -> motor and blade Notes:
  • inifinite control of ground speed is good

IHET2302 - Steeering and Suspension Systems and Accessories

  • Steering
    • rigid frame
      • Front wheel steering
      • Rear wheel steering: fork lift, combine
      • Four wheel steering
        • crab steering: maximum rotation,
          • all four tires turn in the same direction
          • each wheel is on track
          • maximum flotation
        • co-ordinated (circle) steering: tire turning radius
          • rear tire turn on the same track as the front tires. (wheel loader)
      • Combination steering: crab, 2 & 4 wheels
      • Skid steering (skid steer loader)
        • with wheels or with tracks
        • control with pump, left & right track
    • non rigid frame units: Wheels not responsible for steering (articulated steering)
      • wiggle wagon (cab & box can be osciallated), loader, & grader, anything that is articulated
      • wheel loader (co-ordinated steering because of articulated point in the middle of the equipment)
      • tractor scraper (rear tires turn inside of the track)
    • full time power steering has no mechanical connection steering wheel (joy stick) and the turning wheels
      • reservoir, pump
      • pressure control valves: limit system/circuit pressure, sequence (priority) valve
      • flow control valves: limit flow rate, enable comfort steering speed
      • directional control valves (reversing valves):
        • hand metering unit
        • spool type steering valves
    • some system, pilot system has first priority such as loader, (don’t have pilot control, we can not do any things else)
    • same feel no matter what engine rpm, steering should have the same feeling. We need flow control
    • Ackerman principle
    • HMU is a pilot control; controlling streering control valve
    • Neutralizer valves stop steering when it hit the end of travel by cutting hydraulic power
    • Need physical stop pin in case of the spring fails in the HMU
    • The pin is also the drive for the pump
    • 225 / 45 / 17
      • tire width 225
      • aspect ratio 45% of its width, Rubber band of tire
      • size of rim 17in
    • camber: inward and outward of grader (use for stability)
    • negative camber (/—-): improve stability & connering, but causing more tire wear (if we don’t drive fast, don’t need negative camber)
    • positive camber (-–/): nobody uses it, unless they wants lose stability
    • Tie rod is cheap $80
    • Lock pin
    • Steel/rubber cushion: cutting power assist before we hit the stop
    • micron is a million of meter
    • Dont use cheap filter, it’s function is so important, protecting all the hydraulic system
    • Grader wheels does not help it turning, but help it keep equipment go straight
    • services:
      • seize pin, bushing can hard steering
      • ensure it safe for the drive before driving the equipment
      • inspect: loose fastener (tie rod), frayed hose, bent fitting, contaminant on cylinder seal
      • avoid articulate point, driver doesn’t know.
      • doing cycle time, pressure and load test
      • ensure put safety bar on articulation point (2 people, 1 driver, 1 mechanic)
      • adjust “(little) tow in” every time replace tie rod
      • scraper easily to loose traction, push-pull 1 equipment load at the time
      • cushion hitch is a part of suspension
    • skid steering
      • hydrostatic drive: skid steers, excavators, dozers, tank
      • maneuverability: it can turn radius easily
      • small gear drive big gear => gear reduction => multiply torque
      • Using track provides better flotaion (ability to stay on surface of soft ground), but less traction
    • fine mesh screen 100 mesh should be located on the outlet port of the tank
    • the minium vol of tank should be half of charge pump vol measured in gpm (minimum fluid dwell time should be 30s)
  • Suspension
    • Purposes:
      • Maintain traction
      • Transfer load during breaking and accelerating
      • Support the load
      • Provide comfort ride
    • Alignment:
      • axle to fram
      • allow some movement when connering (especial tandem)
    • Cushion-hitch: -
  • Attachments
    • two types of operator protection
      • falling object protective structure (FOPS)
      • roll over protective structure (ROPS)
    • buckets
      • replace cutting edge (can use double cutting edges by using longer bolt)
        • use hammer to support underside of bucket when impacting the bolt
        • can use cutting torch for hard cases.
      • replace teeth by removing the pin on excavator bucket
    • blades
      • winter time can have curb feeler to protect the blade (solid steel)
      • swing
    • ripper (on dozer, road construction)
      • ripper shank dig into the ground
      • Track frame is holding the track and connect with the c-frame in dozer via a trunnion mount
    • winches
      • left lay wire: // => use left hand indicator
      • right lay wire: \ => use right hand indicator
  • Electrical
  • Tracked steering
  • Under carriage (clickety-clack)
  • Off road drive axle + differential
  • Final drive

IHET2303 - Transmission

  • Gears
    • Gear ratio:
      • torque is multiplication
      • speed is division
    • Underrive or gear reduction: small drive large gear (mostly)
      • input 20 gear teeth (drive); input torque 100lbft; input rpm 50
      • output 40 gear teeth (driven)
      • Radio = 40 : 20 = 2 : 1
      • output torque = 100lbft * 2
      • output rpm = 50rpm / 2 = 25 rpm
      • horse power does not change
      • More torque, less speed
    • Override: Large drive small gear
      • input 40 gear teeth (drive); input torque 100lbft; input rpm 50
      • output 20 gear teeth (driven)
      • Radio = 20 : 40 = 0.5 : 1
      • output torque = 100lbft * 0.5 = 50lbft
      • output rpm = 50rpm / 0.5 = 100rpm
      • horse power does not change
      • Less torque, more speed
    • Planetary gear
      • sun gear, planet pinion gear, planet pinion carrier (p.c.), and ring (internal) gear
      • 3 gears: input, output, and held yield 7 scenarios
      • if we don’t have held element, we have neutral
      • sun 12 teeth; ring 36 teeth; pc 38 teeth
      • largest: p.c, medium: ring; smallest: sun
      input output held outcome ratio direction
      sun p.c ring deepest reduction 4:1 forward
      p.c sun ring greatest overdrive 1:4 forward
      ring p.c sun mild reduction 1.33:1 forward
      p.c ring sun mild overdrive 1:1.33 forward
      sun ring p.c reduction 4:1 reverse
      ring sun p.c overdrive 1:4 reverse
      - - any 2 direct drive 1:1 forward
      - - None Neutral -  
    • steps to draw and find speed and torque
      • mark held member
      • xSun —————- Planer —- Ring
      • draw from input speed to held member
      • intersect point @ out member is the speed and direction output
    • pinion and bevel gear (crown or ring gear)
      • purpose: change direction
      • gear reduction
      • gear components
      • looking at somebody, toes are in, heels are out
      • important things: heel, toes, face, & flank gears des
    • too much backlash => cause loosing, oil have hard time to get in,
    • telehandler
    • straight cut
      • pros: cheap, noisy
      • cons: all work done on 2 little teeth
      • ball bearing, control radial thrust
    • helical cut
      • pros:
      • cons: expensive
      • tapered roller bearing, control axial, radial thrust
    • planetary drive
      • typical final drive ratio: 10:1
      • sprocket segment is mounted to planetary carrier
      • The Reason for outboard is to keep smaller driveline components
      • Outboard planetary
        • lubricated by oil via a hole on the rim
        • Sun drive, ring held, and p.c driven (out)
      • lub pocket by flashing
      • double reduction: sun1: in, p.c1: out; ring1: held; p.c1 out to sun2, sun2 drive p.c2, ring2 held
      • don’t want put high gear reduction (20:1) on just 1 gear set because of wear aspect. If we only have 1 gear set, it will suffer more wear.
    • duo cone seal
      • purpose:
      • old one is very sharp, don’t use hand to grab it.
      • on installing, don’t touch it, use bearing installation tools
      • don’t twist the rubber part
      • don’t use lub, use alcohol, windex works ;-)
      • rubber seal compensate for face seal wear
      • prevent oil in differential, trans coming to final drive
    • lip seal (bw sun gear and housing) keep oil in trans don’t go to planetary drive
    • interest movies search keys: stripping shovel, snow train letourneau, white zombie car
    • dc drive
      • normal conf: engine - trans - driveline - rear axle
      • easy maintain, take less hours to replace the motor compared to axle replacement
      • pros:
        • control DC easy
        • fewer moving parts
      • cons:
        • contamination can build up in the brushes assembly in the motor
        • brushless motor is more durable, no wear components (no brush)
    • ac drive
      • pros:
        • no brush
      • cons:
        • control
      • change frequency will change speed
    • filter & capacitor: smooth or clean up DC signal 1
    • rectifer: convert ac to dc
    • inverter (IGBT or GTO): convert dc to ac
    • chapper
    • dynamic braking grid
    • if the motor generates electric from rolling to the hill, we waste these energy as heat!
  • check backlash
  • non-hunting
    • 4:1, 3:1, 2:1
    • need maintain wear pattern as each teeth contact again
  • partial hunting
    • 3.2:1 every 5 revolution teeth contact again
  • hunting
    • 3.73:1, 3.42:1
    • every teeth on the gear meet all teeth of other gear
  • Spartial gear
    • quiet stronger
    • 2 teeth contacts
    • longer teeth
    • For high torque application, we need 3 bearing on pinion to support axial thrust
  • Amboid (top) & hyroid (bottom)
    • amboid has better ground clearance
    • get hugh wiping edge
  • Worm gear, there is no way the worm wheel (load/driven) turning the worm (drive)
  • differential: interwheel, interaxle differential
    • input rpm = (R rpm + L rpm) / 2
    • take power from engine and split the different torque to each wheels
    • path of power
      • input yoke
      • pinion gear (hypoid gear set)
      • bevel, crown, ring gear
      • differential case (rotate with the bevel gear)
      • cross
      • differential pinions (spyders)
      • axle side gears
      • axle shafts
      • spur gear => bull gear => drive sprocket => chain
    • side bearing adjustment
      • we have tapper roller bearing. On setting preload, super important to turn the bevel gear, recheck the backlash after seeing zero end play
    • pinion mount:
      • overhung: pinion has flat top
      • straddle: pinion has bearing on both side
  • drive axle assembly
    • carry the load or support vehicle weight
    • transmit torque with gear reduction
    • change direction of torque
    • normal operation
      • input yoke: 100kmph, 100lbft
      • ring & pinion ratio - 3:1
      • output LH: 100kmph, 150lbft
      • ouput RH: 100kmph, 150lbft
    • Problem of open differential
      • 1 tire has good traction; if it’s has no traction, the other tires will spin at doubled input speed
        • because of the transmission cases design, it’s hard to get oil into transmission case
        • differential pinions spin too fast causing lack of lub; consequently, it’ll melt and weld to the cross
      • input yoke: 100kmph, 100lbft
      • ring & pinion ratio - 3:1
      • output LH: 100kmph, 150lbft
      • ouput RH: 0, 150lbft
    • differential assembly includes cross, differential gears, side gears, differential case.
    • carrier assembly includes bevel gear, input pinion, and differential assembly
    • before pull the axle shaft out, engage the lock, then pull the carrier out
      • for air engage lock, we need remove the air plug, and use a bolt to keep the lock engage.
  • axle housing
    • full floating axle
      • drive axles do not support the weight of equipment
      • the housing and bearing will support the vehicle weight
      • we can pull the axle out (move up and down); the wheel still is in place, not fall off
      • ring gear is bolted to the housing, sun is the drive element, output is p.c
      • step to remove: remove the axle flange bolts, move axle up and down to remove it.
    • inboard:
      • planetary gear seat next to differential assembly
      • need big axle
      • better lubrication by using transmission oil
    • outboard:
      • planetary seat in drive end wheel
      • smaller axle
      • better axle clearance
    • we need more drive axle because we need more traction
  • transfer case: use one input driving font & back axles
    • just like a carrier assembly, but LH and RH sides gear drive font and back axles
    • split torque and speed between font and back axles
    • it’s lockable
    • typical ratio: 1:1 or 1.5:1 (in read life, most of the time, we use 1 point something ‘small’ instead of 1:1)
    • can use planetary with different size pinions to change torque, but keep the same speed
      • this setup does not have ring gear input shafts transfer torque to transfer gear to p.c then side gears
      • input 1000lbft, font get 400lbft, back get 600lbft which split to 300lbft for each rear axles.
      • keep the same input speed in normal running condition
    • Mack input in p.c, output sun to the front, output ring to rear
      • p.c drive sun : font receives 40% torque
      • p.c drive ring : back receives 60% torque
  • tandem drive
    • receive 60% from transfer case, slipt equally to each rear axles
  • (fun) unimog: multipurpose German trunk, ton of ground clearance because of different side axle connect to a spur gear, a bull gear, and wheel
  • prevent 1 tire rotating on ice, other does not move
    • jaw or dog lock most common (simplest):
      • stop differential side gears from turning by locking axles to differential case
      • use square cut dot teeth, not engage perfectly
    • no-spin differential:
      • lock differential all the time, disengage on cornering
      • dis: if the axel is broken, we don’t know; until, the whole carrier is broken
    • jteckt torsen differential: automobile, toyota
    • pinion and spring push cone clutch to housing to lock differential
    • pinions and gears are lub by flashing oil
    • drain plug is either out or tight, not hand tight.
    • hot housing will build pressure, push out seals; thus we need breather on housing.
    • suspension loose (u bolt) can cause crack on axle housing
    • get hammer hit the u bolt, check for any thing shiny in suspension if any.
  • service carrier
    • etch number is positive 3thou indicating the pinion must sit 3thou further away from bevel gear
    • etch number is negative, doing opposite
    • adjust pinion to ring gear
      • shim between bearing cage and carrier: thicker, further
      • use spacer between inner pinion bearing and the pinion gear: thicker, closer
    • adjust backlash and pattern:
      • move ring gear to pinion, lower the pattern (affect heel and toe) by adjusting the adjusting ring on the side
  • Service drive axle
    • noise in drive shaft can transfer to transmission to driver cab.
    • transmission can transfer its vibration to drive shaft as well.
    • look for shiny things, loose u-bolt, things moving
    • check drain magnetic plug, looking for pieces (junks) in the nut.
    • vibration usually comes from the back side.
    • check oil level
    • put the equipment on stand, run it @ a certain speed, see if equipment vibrates
      • start from back, pull axle shaft out; thus, eliminating tire components
      • move to next axle, pull axle shaft out, see if there’s vibration
    • check drive line angle (really effect vibration)
    • do a visual inspection before going on road test, before pulling for anything any
    • noise on drive: bearing problem
    • on turn: diffrential case
    • on coast: pinion and ring gear too tight
      • coasting (go down hill) there is no load on gear, load pushing it
      • adjust the gear clearance.
    • put to much silicon on carrier can cause it entering oil, plug flashing oil that direct oil bearing
    • prechecks
      • bevel backlash (hunting gear set)
      • runout
      • contact pattern
      • bearing preload
      • mark the bearing cap before dismantle
    • back side have large bearing, (support the ring will be pushed back, more thrust)
    • the ball ring tooth uses adjust preload, then adjust pattern
    • pinion spacer determine preload
      • thicker spacer, less preload
      • thinner spacer, more preload
    • splines on axle shaft can be worn; it causes split
    • pitting on pinion: metal-to-metal contact, not having lub
    • scoring: don’t have enough lub
    • fracture of ring gear at the tooth toe: incorrect backlash
    • assembly
      • to check preload of pinion, setting up on press, spring scale specs, need to do math from middle of pinion to the edge of pinion cage
      • we don’t put sealant on pinion shim, its ok to see a little bit dirt around shim
      • readjust backlash after adjust pattern
        • pinion out => face
        • pinion in => flank
  • tracked type equipment: dozers, tracked loaders, skid steers, excavators, shovels, cranes, n.a.s.a, side booms, tanks, AG.
    • control levers in normal position: clutch engages, break released.
    • power delivered to final drives through the steering clutches
    • priority valve ensure oil flow from transmission pump to the steering clutch and brake before flowing to transmission or torque converter
    • use the most narrow shoes, reduce seal problem
    • working on side hill, need change direction to wear normal
    • daily inspection, leaking seal, loose bolt
    • keep it cleaned
    • operators affect tracked-type tractor’s life
      • minimize high operating speed, do not high speed reverse
      • alternative directions => allow even wear
      • don’t spin, rotate side to side
    • wear factor
      • load
      • motion (depend on how we use it)
      • contact with ground
    • bushing turning in the sprocket is not good, twice the wear. Reverse can bushing turning in sprocket
    • install chain in reverse cause opposite effect on wear: reverse is now good, but forward will cause major wear
    • low drive:
      • 5, 4 under load: -> more teeth in contact -> more torque, less load
      • low center gravity, increase stability
    • high drive (only cat):
      • less teeth contact, more load, thus causing more wear
      • 2 idlers: more components to wear
      • prevent damage from shock load of sprocket
      • easy to work on
    • carry load
      • traction: use narrow pad
      • floatation: use wide pad
      • stability
    • components:
      • track shoes (pads)
        • dozer (D11), whole jobs is to push, single grouser (the most aggressive traction)
        • 1 grouser (standar), multi-grouser (street pads)
        • (3 grouser) excavator, moving not pushing, get more floation, don’t need aggressive grouser
          • some holes allow mud come out, self-cleaning
        • rubber shoes design reduce damage to the pavement, used in warehouse
      • carrier roller:
        • mounted on top of the track frame
        • supporting the weight of the top track
      • track roller:
        • alternatively installed on the bottom of the track frame, start with double, single, double, single (save money)
        • keep track align
        • support the weight of the machine
      • idler in front
        • align the track
        • can be shim in the mouting frame to align the track
      • pan hard bar can’t not adjust to change track toe
      • sprocket driven by final drive at the back
        • sprocket worn, bushing will worn
        • sprocket segments: easy to replace, maintain, can service by flip it
      • track sag(measure on top of grouser): ideal 4.5” measured from center line of sprocket to idler by a straight edge
        • track and bushing wear causing track seem longer
      • recoil:
        • control shock loads caused by track impact
        • nitrogen charge, add grease (rod end) to loose the track (use in big equipment, i.e shovels)
        • spring tension, add grease (based end) to tighten the track
    • track adjustment
      • tension
        • forward direction straight
        • coast to stop
      • loose / damaged components
        • sign of oil leak
        • pin has oil leakage, not a big problem, leave it => run to destruction
      • misalignment
        • roller wear on one side (effected by poor operator driving on side hill), can caused by track misaligned
    • undercarriage wear
      • pins - bushings - sprockets wear most
    • frame
      • measure font and back => check alignment, say less that 1/2”
    • mounting surface, such as sprocket segments, have to be cleaned (removing all paint if any). Paint can be thick as 0.016”.
    • equalizer bard or pivot bar
    • rubber track : good floatation, pavement, agriculture
  • Powers automatic transmission
  • Clutch types (overcenter clutch)

Province Exam

  • Hydraulic 55
  • Powertrain 47
  • Steering, suspension, accessories, apprentiship 18


  1. a dc signal