Suspension System Fundamentals and Service Flashcards
Identify five functions of an off road suspension system as outlined in this module.
a. Have a specific load carrying capacity for each particular application.
b. Absorb and transmist torque loads to the vehicle frame.
c. Respond quickly to changes in terrian so that the tires contact the ground.
d. Provide a cushioning effect to increase operator comfort and protect the vehicle.
e. Position axle assembly accurately in relation to the driveline, on mechanical drive machines.
A cushion hitch system acts as a connection device, a suspension device and as part of the steering system.
True
On a cushion hitch assembly, identify the major component that is attached to the rod end of a load cylinder.
The rod end of the load cylinder is attached to the scraper hitch portion of the cushion hitch assembly.
Identify the two major types of suspension systems used with off road haul trucks.
a. rubber block type.
b. Hydro pneumatic type.
Explain how the load cylinder and accumulator operate as a unit when the cushion ride feature is selected and the ground is rough.
As the machine moves over uneven ground, with the cushion ride feature selected, oil from the load cylinder moves into the accumulator forces the accumulator piston upward. This action further compresses the nitrogen gas above each piston. When the pressure of the compressed nitrogen gas exceeds the pressure of the hydraulic oil, the accumulator piston is forced downward. This action causes oil to return into the head end of the load cylinder. The oil returning into the load cylinder causes the rod to extend. This action re-establishes the normal operating clearance between the bracket and scraper hitch assembly.
The hydraulic system does not have to be depressurized before the hydraulic system components are removed, opened, adjusted or loosened.
False
The condition of an axial piston type of hydraulic pump can be determined in part by the results of an oil leakage test.
True
When you are charging or testing cushion hitch accumulators, you must:
a. wear safety glasses and gloves during the procedure.
b. follow the specific instructions provided by the particular manufacturer of the test equipment.
c. consult a temperature compensating chart for the particular type of accumulator.
d. conduct the charging or testing procedure in a specific sequence of steps.
e. do all of the above.
e. all of the above.
Explain the basic operation of a hydropneumatic suspension cylinder as the truck moves over rough terrain.
When a truck moves over a bump on the ground the rod and piston assembly move upward in the cylinder bore. Nitrogen gas above the piston is compressed to a greater degree than its preset charge. Oil beneath the piston is forced through a check valve and an orifice into a cavity between the cylinder bore and the rod. When the truck passes the bump the weight of the truck and cargo and compressed nitrogen gas force the piston and rod assembly downward. The check valve is closed and oil is forced back under the piston through an orifice. As the orifice is slowly closed the piston speed slows.
The grease fittings on the rear hydro pneumatic suspension cylinder bearings are typically lubricated at a central lubrication point.
True
Explain the purpose of a payload pressure sensing valve, as used on some suspension cylinders.
The payload pressure sensing valve senses hydrair nitrogen gas pressure and converts that reading into an electrical signal. Signal is sent to a monitoring system that converts it into a weight measurement. This helps to determine the operating performance of the truck during a work shift.
Whenever a haul truck body section must be raised, or whenever the articulated steering must be secured, proper safety devices must be used.
True
A tractor scraper can be equipped with either a basic hitch system or a cushion hitch system.
True
The tractor bracket is attached to the tractor while the scraper hitch assembly is attached to the scraper.
True
On a cushion hitch assembly, identify the major component that is attached to the head end of the load cylinder.
The head end of the load cylinder is attached to the tractor bracket assembly that is attached to the trailer section.
