190302b

Question 1

functions of off road suspension systems?

Answer 1

1. have a specific load carrying capacity
2. absorb, transmit torque loads
3. provide cushioning + operator comfort
4. position axle assembly in relation to driveline
5. allow each axle assembly to move independently of each other

Question 2

what can help reduce scraper load time?

Answer 2

by using a push dozer or push pull configuration

Question 3

what did the tractor scraper evolve from?

Answer 3

crawler and pull scraper using a cable control unit

Question 4

what are the two sections on a scraper?

Answer 4

the front tractor and rear bowl

Question 5

on a scraper, why was a non-cushion hitch called a stiffneck?

Answer 5

didn’t allow for vertical movement

Question 6

what is the main function of a non-cushion and cushion hitch system?

Answer 6

act as a connection device when it is mounted between the scraper and the tractor

Question 7

What is the cushion hitch able to control?

Answer 7

the severity of vertical movements

Question 8

where does the head end of the cylinder pin to on a scraper hitch?

Answer 8

pins to tractor bracket

Question 9

where does the rod end of the cylinder pin to on a scraper hitch?

Answer 9

pins to the top of the scraper hitchw

Question 10

what provides the steering pivot point between the tractor and the scraper?

Answer 10

the vertical pins connecting the scraper hitch to the gooseneck

Question 11

what does the cushion hitch hydraulic components consist of?

Answer 11

one or two accumulators
a leaf spring (levelling valve)
a control lever in the cab
an accumulator hyd bleed valve
a variable displacement pump
load cylinder
connecting lines

Question 12

what type of suspension system is usually used in smaller haul trucks?

Answer 12

rubber block

Question 13

what type of suspension system is used in larger haul trucks?

Answer 13

hydropneumatic

Question 14

Where are the rubber blocks located on a suspension system?

Answer 14

above the axle housing, below the walking beam

Question 15

what is a pan hard rod used for?

Answer 15

keep drive axle housing accurately centred, left to right, in relation to the truck frame

Question 16

when a scraper is loading or finishing, what is the suspension system doing?

Answer 16

being in lockdown

Question 17

when hauling, dumping, and returning to the cut area, the machine can develop a ______ motion?

Answer 17

loping

Question 18

what does the cushion hitch hyd system share with the rest of the hyd system?

Answer 18

the reservoir

Question 19

what are the 3 positions used with a twin engine tractor scraper?

Answer 19

bail down, lockdown
bail up, lockdown
cushion ride

Question 20

when is the cushion ride option only available?

Answer 20

when the tractor scraper is under its own power

Question 21

if you leave the hitch and bail up and shut down the machine, where will these components be in the morning?

Answer 21

lowered down as hyd oil will return to tank

Question 22

what is the control of excessive vertical movements during operation on a cushion hitch a direct result of?

Answer 22

compression and expansion of the nitrogen gas in the accumulators

Question 23

when does max oil flow occur on the hyd pump for cushion hitch?

Answer 23

when the output oil pressure is less than the pressure setting of the hyd pump servo valve

Question 24

what does the control piston do in a pressure servo valve?

Answer 24

moves the pump swashplate toward its minimum operating angle

Question 25

before removing any lines or components on a scraper hitch, what should you first do?

Answer 25

visual inspection

Question 26

how do you remove pressure in a hyd system on a scraper?

Answer 26

move each hyd control through all operating positions several times and slow loosen filler cap to hyd tank

Question 27

how do you adjust the linkage between the levelling valve and leaf spring?

Answer 27

turn the yoke on the linkage

Question 28

how is hyd pump performance determined?

Answer 28

in a percent of flow loss test

Question 29

what is a way to test for leakage in an axial piston type pump used in the cushion hitch suspension?

Answer 29

oil leakage test

Question 30

rpm and pressure goes up,

Answer 30

oil leakage goes up

Question 31

what gas is used in accumulators?

Answer 31

dry nitrogen 99.8%

Question 32

what should you charge the nitrogen gas to?

Answer 32

the ambient temperature rating

Question 33

charging pressure is less when the temperature is low and greater when the temp is high T or F

Answer 33

T

Question 34

How do you check the nitrogen charge in an accumulator?

Answer 34

with proper test equipment, use a thermometer to determine temp, then determine required nitrogen charge pressure

Question 35

what should you first do when an accumulator is new or rebuilt?

Answer 35

our 2 quarts sae 10w hyd oil into nitrogen end, then bleed out the oil

Question 36

What is the basic function of a haul truck suspension system?

Answer 36

provide operator with a comfortable ride and reduce stresses imposed on the machine

Question 37

what is the purpose of rubber block suspension?

Answer 37

dampen vertical forces

Question 38

what is the purpose of the pan hard rod?

Answer 38

positions axles laterally in relation to machine frame

Question 39

what is the purpose of the a frame?

Answer 39

positions drive axles front to rear. provides longitude support + transfer forces created via wheel torque

Question 40

are rubber blocks self compensating for load?

Answer 40

yes

Question 41

do you need shock absorbers with hydro pneumatic cylinders

Answer 41

no

Question 42

how does the shock absorber motion work with hydropneumatic cylinders?

Answer 42

compressing the nitrogen gas by moving the rod and piston in operation

Question 43

what do the hydrair upper and lower bearings on the mounting points provide?

Answer 43

bearings allow strut to move slightly as weight changes

Question 44

what are the wear bars used for on each side of the strut bearing surfaces?

Answer 44

limit strut movement (twist)

Question 45

how do you measure payload weight on a haul truck?

Answer 45

payload pressure sensors monitor nitrogen gas charge pressure

Question 46

how do you check a suspension cylinder without disrupting the charging process?

Answer 46

coast the truck to a stop without using the brakes to ensure cylinders will not depress.