190303gB Flashcards
As equipment becomes heavier what type of steering is more likely to be seen?
Differential steering, it is less likely to see hydrostatic steering
Is there a torque converter involved in the hydrostatic crawler tractor steering system?
No
Why would a skid steer creap?
Something is out of adjustment, the swash plates are not in an equal neutral position.
What position is a swashplate in when 0 GPM are flowing?
Zero Center (Neutral)
What happens in a skid steer when the swashplate is pushed over center?
Reverse, do to the change in outlet port from the pump.
What angle should the swashplate be in to get maximum speed (GPM)?
At max angle, allowing pistons to achieve full stroke, pushing max GPM
What is max torque in a hydraulic system?
Max Pressure
How do you achieve maximum torque (pressure) with a swashplate?
The swashplate must be at minimum angle
What is the first rule to remember in Hydrostatic (hydraulic) motors?
Rule 1. The swashplate never EVER goes to zero angle or neutral.
What is counter-rotate?
Equipment turns within its own length usually by rotating one track forward and one track in reverse
In a dual path hydrostatic system used to control speed and direction, is the system a closed or open circuit?
Closed circuit (2)
What type of pumps are used in dual path hydrostatic systems with two closed circuit drive systems?
Two variable displacement reversible pumps, axial type piston pumps
What drives the pumps needed for steerng?
“Tractor” Engine
What condition is the piece of equipment in when two track motors are rotating at the same speed?
Forward, Straight
What is done to the pump and motor to change track speed?
The operator varies the displacement of each pump and motor
How is a tight turn achieved with hydrostatic systems?
One track is driven and the other is in a neutral position. (Pivot Turn)
What is an advantage of using hydrostatic steering systems compared to clutch steering?
Power is applied to both tracks when the tractor is being turned
Infinitely variable track speed and counter rotation makes the machine more maneuverable
Optimum traction can be achieved, making the machine more productive
What type of control system is used on most hydrostatic steering systems?
Electronic Control System
What are some components of the hydraulic side of a hydrostatic steering system?
Charge Pump Neutral Charge Relief Valve Charge Filter Hydrostatic Pumps Hydrostatic Motors Check Valves High Pressure Relief Valves Flushing Valve Pressure Control Pilot Operating Charge Relief Valve Pump Displacement Control Valve Motor Pressure Control Pilot Valve Motor Displacement Control Valve Cooler and Bypass Valve
What are some electronic components in a hydrostatic steering system?
Engine Speed Control Sensor Left/Right Steer Sensor Decelerator Sensor Speed Control Sensor Forward/ Neutral/ Reverse Sensor (FNR)
What happens to a torque converter when brakes are applied on equipment with a steering differential?
The torque converter will stall
What are the advantages hydrostatic drive has over power shift? (4)
Easy to operate, no learning curve (smoother operation)
Power is applied to both tracks when turning
Infinitely variable track sped, count-rotate
Infinite speed control, ground speed is adjustable to provide optimum traction
How is a pivot turn achieved in a dual path hydrostatic system?
One hydrostatic pump is in the neutral position and the other is rotated.
What is one way to describe a counter-rotate?
Equipment turning within its own length
Describe closed loop systems?
The fluid does not return to “tank” it returns to the inlet of the pump
Describe an open loop system
Fluid will return to tank before being picked up by the pump
Charge Pump is ran at what speed?
Engine RPM, 100% duty cycle
What are the jobs of the charge pump?
- Replenishes internal leakage
- Supercharges piston pump inlet (piston pumps cannot draw in oil well)
- Changes closed loop oil through low pressure side
- Supplies control pressure
How many filters are apart of the closed loop system?
None on average, special equipment can be designed to have them
What is pilot pressure also known as?
Charge pump pressure
What position does the motor displacement control valve always default too?
Low Speed, High Torque (turtle)
What type of hydrostatic motors are used to drive the final drives?
Variable displacement, bent axis
What is the basic purpose of the flushing valve?
To change the oil in the closed loop, efficient cooler
What is another name or description of a pressure control pilot valve?
Electrohydraulic servo valve
In relation to pumps, how many pressure control pilot valves are there in a system?
Most systems have two, one for every pump
What operates the pump displacement control valve?
Signal from the ECU to the pressure control pilot valve, changes elect signal to a pressure differential signal
