190303gB tracked equipment steering part B

Question 1

what angle is the swashplate in a hydrostatic pump when maximum speed and minimum torque is wanted? and what is the angle of the swash plate on the motor?

Answer 1

The angle of the pump swashplate is maximum, and the angle of the motor is minimum

Question 2

what angle is the swashplate in a hydrostatic pump when minimum speed and high torque is wanted? and what is the angle of the swash plate on the motor?

Answer 2

The angle of the pump swashplate is minimum, and the angle of the motor is maximum

Question 3

What allows steering on a hydrostatic skid steer?

Answer 3

more power sent to one motor than the other to allow steering in the desired direction

Question 4

If you want to do a right turn which motor receives more power?

Answer 4

the left motor

Question 5

on a ISO symbol, if the arrows are pointing inwards, inside a circle (on both sides) with an arrow through it what does that represent?

Answer 5

a reversible, variable speed motor

Question 6

on a ISO symbol, if the arrows are pointing outwards, inside a circle (on both sides) with an arrow through it what does that represent?

Answer 6

A reversible variable speed pump

Question 7

if a one track is moving forward, and one is moving backward, and it turns within its own length, what is the steering condition called?

Answer 7

counter rotate

Question 8

What are some of the advantages to hydrostatic steering?

Answer 8

power is applied to both tracks when the machine is being turned, more manoeuvrable, machine ground speed can be adjusted for optimum traction

Question 9

What are the two rules to a hydrostatic pump?

Answer 9

1.The swashplate can go to zero (not moving oil) 2. The swashplate can go over center and reverse oil flow

Question 10

What are the two rules to a hydrostatic motor? explain them?

Answer 10

1. The swashplate never goes to zero angle (the oil sort of acts like a brake, and it would blow up if it was able to) 2. swashplate never goes over center

Question 11

What makes a hydrostatic motor “variable”?

Answer 11

it would be a 2 speed motor, 2 servo pistons would give it two different angles for speed and torque control

Question 12

Why do you require a charge pump on a closed loop system?

Answer 12

to make up for leakage in the closed loop system and also because a hydrostatic pump cannot pull a vacuum

Question 13

Where does the neutral relief valve dump its oil when in relief, then where does it head?

Answer 13

to the hydrostatic pump case for cooling and lubrication, from there it goes to a case drain through the oil cooler back to tank

Question 14

where is the filter normally located on a closed loop system?

Answer 14

the outlet line from the charge pump

Question 15

when the closed loop system is in operation, which component replaces leakage oil, and on which side of the closed loop system during said operation?

Answer 15

the check valve adds make up oil to the system on the low side

Question 16

if the closed loop system built up enough pressure to go over relief, where would that oil go to?

Answer 16

out through the neutral relief valve to case drain then to oil cooler and then to tank (or just tank would be an acceptable answer)

Question 17

what is the purpose of the shuttle or flushing valve?

Answer 17

allow oil to be sent to the operating charge relief valve of the hydrostatic motor, through the case drain for cooling and lubrication

Question 18

what is the purpose of the operating charge relief valve

Answer 18

send cooled oil to the case of the hydrostatic motors for cooling and lubrication, and put resistance on the low pressure side so you don’t cavitate the pumps

Question 19

how is pilot pressure controlled in some systems? and what does it control?

Answer 19

controlled by solenoids, which send pressure to a displacement control valve which controls the hydrostatic pump swashplate

Question 20

what component would the case drain go through before heading to tank drain?

Answer 20

an oil cooler and bypass valve

Question 21

machine is a hydrostatic skid steer, operator complaint is when going forward, machine is fine, going in reverse one track won’t move, what could potentially be an issue?

Answer 21

any component opposite to flow of forward, on the high side could be an issue : check valves, relief valve, shuttle valve

Question 22

how would you safely work on a machine with pilot pressure or a closed loop system?

Answer 22

let machine sit, and let oil leak down, as there will be a little bit of leak down as the motors and pumps are not 100% efficient

Question 23

what controls the swashplate on a motor, or hydrostatic pump?

Answer 23

a servo piston controlled by hydraulic pressure, electric solenoid, or mechanical link

Question 24

what is the benefit of a closed loop electronic system? and how does it work?

Answer 24

allows diagnostics, output goes through sensors, sensors supply current output back to ecu

Question 25

what is a closed loop hydraulic system?

Answer 25

oil is allowed to circulate back and forth between a hydrostatic motor and pump within a hydraulic system, basically the oil stays in its own loop.

Question 26

what is an open loop hydraulic system?

Answer 26

oil is taken from the hydraulic tank, and sent through the system, back to tank

Question 27

What are the benefits of a full electronic system for hydrostatic systems?

Answer 27

through sensors, and controllers the system can monitor machine tracking and adjust pressures and values to keep the machine running absolutely precise, also can monitor engine rpm so as to not allow the operator to overload the machine based on speed and load, allows on board diagnostics

Question 28

In a CAT differential steer system when travelling in a straight line both sides of the dif experience a _______ reduction and have the ________ rpm

Answer 28

Experience a TRIPLE reduction and the SAME rpm

Question 29

what components make up a differential steering system

Answer 29

A steering differential gear set, a hydraulic pump, and hydraulic steering motor, and steering controls

Question 30

what are the inputs and outputs on a differential steering system?

Answer 30

power input from the transmission, input from a hydraulic steering motor, two outputs one to each final drive (or planetary)

Question 31

two groups of hydraulic components are required for differential steering?

Answer 31

steering system hydraulic components, and brake system components

Question 32

what are the two hydraulic components required for the steering system?

Answer 32

a proportional directional control valve, and a closed center hydrostatic drive

Question 33

What would the planetary gear sets be doing in a differential steer system when steering?

Answer 33

one gear set carrier would be spinning faster, which would cause the output to spin faster and the other side ring gear would start spinning in the opposite direction to slow down that gear set, thus allowing more power to be sent to one side and less to the other side

Question 34

What is the differential crown gear attached to in a differential steer system?

Answer 34

the crown gear is attached to a housing which is attached to the internal gear on the planetary

Question 35

going straight what speed is the differential steering motor moving at?

Answer 35

0 rpm

Question 36

if an operator requires more steering what will the differential steering motor do?

Answer 36

it will turn faster to provide more power to one track or final drive through the planetaries

Question 37

would the transmission output speed change if steering is required while moving in a differential steer system?

Answer 37

No it would stay the same, the planetary action will change the speeds on either side of the differential based on what the differential motor is doing

Question 38

How would a differential steer system achieve a counter rotate condition? and would it really be a full counter rotate in theory?

Answer 38

an operator would put the transmission into neutral and turn whichever desired direction and the machine would do a counter rotate, but it would not be considered a full counter rotate as it would not be turning within its own length

Question 39

What type of brakes are on the differential steer system? how are they applied and released? and do they help with steering?

Answer 39

wet disc brakes, that are applied by hydraulic pressure and released by springs and they will not help with steering.

Question 40

When doing a turn diameter check, with a differential steer unit what should ground conditions be?

Answer 40

should be done under maximum traction, dirt is maximum traction on a dozer

Question 41

what are you checking when doing a turn diameter check on a differential steer unit?

Answer 41

to see if your steering motor is rotating at maximum rated speed.

Question 42

what are you checking when doing a sprocket speed difference check?

Answer 42

the difference in speed between the two sides of the differential steering motor speed

Question 43

how does the ecu monitor machine tracking? what are they checking?

Answer 43

by monitoring the left and right speed sensors, which monitor motor speed

Question 44

why is there a speed sensor monitoring pump speed?

Answer 44

its a signal to ensure that when engine rpm drops, ground speed will slow to handle the load being put on it

Question 45

2 sources of input power to a steering differential are?

Answer 45

transmission and steering motor