190303gB tracked equipment steering part B Flashcards
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?
The angle of the pump swashplate is maximum, and the angle of the motor is minimum
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?
The angle of the pump swashplate is minimum, and the angle of the motor is maximum
What allows steering on a hydrostatic skid steer?
more power sent to one motor than the other to allow steering in the desired direction
If you want to do a right turn which motor receives more power?
the left motor
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?
a reversible, variable speed motor
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?
A reversible variable speed pump
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?
counter rotate
What are some of the advantages to hydrostatic steering?
power is applied to both tracks when the machine is being turned, more manoeuvrable, machine ground speed can be adjusted for optimum traction
What are the two rules to a hydrostatic pump?
1.The swashplate can go to zero (not moving oil) 2. The swashplate can go over center and reverse oil flow
What are the two rules to a hydrostatic motor? explain them?
- 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
What makes a hydrostatic motor “variable”?
it would be a 2 speed motor, 2 servo pistons would give it two different angles for speed and torque control
Why do you require a charge pump on a closed loop system?
to make up for leakage in the closed loop system and also because a hydrostatic pump cannot pull a vacuum
Where does the neutral relief valve dump its oil when in relief, then where does it head?
to the hydrostatic pump case for cooling and lubrication, from there it goes to a case drain through the oil cooler back to tank
where is the filter normally located on a closed loop system?
the outlet line from the charge pump
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?
the check valve adds make up oil to the system on the low side
if the closed loop system built up enough pressure to go over relief, where would that oil go to?
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)
what is the purpose of the shuttle or flushing valve?
allow oil to be sent to the operating charge relief valve of the hydrostatic motor, through the case drain for cooling and lubrication
what is the purpose of the operating charge relief valve
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
how is pilot pressure controlled in some systems? and what does it control?
controlled by solenoids, which send pressure to a displacement control valve which controls the hydrostatic pump swashplate
what component would the case drain go through before heading to tank drain?
an oil cooler and bypass valve
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?
any component opposite to flow of forward, on the high side could be an issue : check valves, relief valve, shuttle valve
how would you safely work on a machine with pilot pressure or a closed loop system?
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
what controls the swashplate on a motor, or hydrostatic pump?
a servo piston controlled by hydraulic pressure, electric solenoid, or mechanical link
what is the benefit of a closed loop electronic system? and how does it work?
allows diagnostics, output goes through sensors, sensors supply current output back to ecu
what is a closed loop hydraulic system?
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.
what is an open loop hydraulic system?
oil is taken from the hydraulic tank, and sent through the system, back to tank
What are the benefits of a full electronic system for hydrostatic systems?
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
In a CAT differential steer system when travelling in a straight line both sides of the dif experience a _______ reduction and have the ________ rpm
Experience a TRIPLE reduction and the SAME rpm
what components make up a differential steering system
A steering differential gear set, a hydraulic pump, and hydraulic steering motor, and steering controls
what are the inputs and outputs on a differential steering system?
power input from the transmission, input from a hydraulic steering motor, two outputs one to each final drive (or planetary)
two groups of hydraulic components are required for differential steering?
steering system hydraulic components, and brake system components
what are the two hydraulic components required for the steering system?
a proportional directional control valve, and a closed center hydrostatic drive
What would the planetary gear sets be doing in a differential steer system when steering?
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
What is the differential crown gear attached to in a differential steer system?
the crown gear is attached to a housing which is attached to the internal gear on the planetary
going straight what speed is the differential steering motor moving at?
0 rpm
if an operator requires more steering what will the differential steering motor do?
it will turn faster to provide more power to one track or final drive through the planetaries
would the transmission output speed change if steering is required while moving in a differential steer system?
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
How would a differential steer system achieve a counter rotate condition? and would it really be a full counter rotate in theory?
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
What type of brakes are on the differential steer system? how are they applied and released? and do they help with steering?
wet disc brakes, that are applied by hydraulic pressure and released by springs and they will not help with steering.
When doing a turn diameter check, with a differential steer unit what should ground conditions be?
should be done under maximum traction, dirt is maximum traction on a dozer
what are you checking when doing a turn diameter check on a differential steer unit?
to see if your steering motor is rotating at maximum rated speed.
what are you checking when doing a sprocket speed difference check?
the difference in speed between the two sides of the differential steering motor speed
how does the ecu monitor machine tracking? what are they checking?
by monitoring the left and right speed sensors, which monitor motor speed
why is there a speed sensor monitoring pump speed?
its a signal to ensure that when engine rpm drops, ground speed will slow to handle the load being put on it
2 sources of input power to a steering differential are?
transmission and steering motor
