190303i Flashcards
Identify two (2) functions of a final drive system.
a) Provide a means of gaining additional powertrain torque multiplication.
b) Absorb shock loads imposed on the powertrain due to operation in harsh off-road
environments.
Planetary final drive systems can be identified as inboard mounted or outboard
mounted.
true
Explain what is meant by the term outboard mounted, when describing planetary
final drive systems.
The term outboard mounted refers to the location of the planetary final drive system.
An outboard mounted planetary final drive is positioned at the wheel or sprocket
List one possible disadvantage of an inboard mounted final drive.
The size of the output components must increase substantially to manage the
increased output torque of the final drive.
The final drive housings on many motor graders act very similar to which component
of an on-highway truck?
walking beam
On wheeled equipment, the most common gearing configuration used in single
planetary final drives is a:
first speed reduction.
Chain drives are typically simpler in design and more cost effective to produce and
operate than comparable gear boxes.
true
The inverter phase module converts:
DC to AC for the traction motors in propel mode
The choppers control the amount of current flow through the:
resistive grids during dynamic braking
. A low DC bus voltage must be verified prior to working in which areas of an AC
drive system?
all areas which are exposed to high voltage
What are the two (2) layers of gloves that must be worn when working on high
voltage systems?
rubber inner and leather outer gloves
What is the minimum safe working distance for a technician wearing full PPE when
testing a system for high voltage?
30 cm (12”)
Tracked equipment may be equipped with the following 4 types of final drive systems
- Spur gear single reduction
- Planetary gear single reduction
- Spur gear double reduction
- Planetary gear double reduction
Two gears in mesh can be used as a final drive gear reduction system. What must be true in order to achieve a gear reduction?
A small diameter gear drives a large diameter gear.
When a planetary final drive is used on a tracked machine, the last gear reduction is
between the drive sprocket and the track chain.
false
Final to chain is 1:1
Clean lubricant and cleanliness during the level check and lubricant filling process
will greatly extend the life of final drive components.
true
Final drive components may be lubricated by splash and/or pressure lubrication
systems.
true
Sometimes a drive sprocket on a crawler must be removed before you can access the
final drive components. When you pull the sprocket off the drive hub with a
hydraulic press, you must ensure the sprocket does not fly across the shop when it
pops free. The service manual will explain this safety process.
true
AC Drive systems usually have higher _______ then DC systems
Efficiency
Why do AC drive systems use solid-state inverters without any moving parts?
Inverters are much faster and more responsive
DC generators use slip rings and DC motors have commutators and brushes. What do these components require?
Ongoing maintenance
True of false.
Electric easy drive is more fuel-efficient?
True
What are some advantages of AC drive over mechanical Drive?
Long component lifespans
Brushless generators and motors are commonly benchmark out to 30,000 operating hours and a relatively maintenance free
The ability to run the diesel engine at a constant speed is desirable and the lack of ship shock increase overall drivetrain life
Engine and generator are often exchanged as a unit which limits downtime
offers great retarding abilities
Less oil consumption over their lifespan due to the lack of the transmission torque converter and differential oil’s
Where does power for AC Drive truck come from?
Engine driven generator or alternator
The brushless generator is an electro mechanical device that converts _____ energy from the diesel engine into _______ energy
Mechanical
Electrical
What are the five functions of the main control group?
1) it converts three wave AC voltage from the generator into DC bus voltage through rectifier assemblies
2) it converts it DC bus voltage to three wave AC voltage for the wheel traction motors through phase modules
3) it protects the phase modules and the dynamic retarding inverter by using capacitors to filter and store DC bus voltage as well as absorb any transient DC voltage spikes
4) it controls the amount of DC bus voltage flowing to the dynamic retarding grids my operating the high-voltage contactors and the retarder chopper
5) it regulates the speed of three wave AC retarding grid blower motor by controlling the operation of the dynamic retarding inverter
How do AC drives controls speed and torque of the traction motors?
By varying the voltage and frequency supplied to the motors
During propel mode what do the inverters do?
During propel mode the inverters using pulse width modulation cooutnvert DC voltage of the DC bus into variable frequency three-wave AC voltage for the wheel traction motors
Which configuration of planetary final drive allows for smaller power train components upstream? (Inboard or Outboard)
Outboard.
An advantage of the outboard planetary final drive is ease of maintenance and servicing. (T/F)
True.
What is the most unique design characteristic of excavator and skid steer and snow cat final drives?
The internal gears for both planetary sets are manufactured as part of the final drives output component. (The drive sprocket housing)
How do you get the overall ratio of a planetary when there is more than one stage group?
Multiply the ratios together
What weight of excavator would use a double reduction reverse planetary final drive?
Common up to 20,000 KG (44,000 pounds)
What weight excavator would use a triple reduction reverse final drive?
Above 20,000 KG (44,000 pounds)
Final drive lubricants can be specially formulated to?
- Withstand high operating temperature
- Flow well at low ambient temperature
- Provide extreme pressure protection for gear teeth
- Provide the frictional characteristics required for wet brake and clutch systems
If a final drive is over full and possibly pressurized what could be the cause?
Internal seal failure. (Brakes leaking into the final drive)
Many finals are not vented to atmosphere. Why?
Due to their rotational operation. This often causes pressurization. Exercise caution when removing the check/fill plug.
Why would a manufacture recommend to remove/drain final oil while it is still hot?
To ensure oil will drain quickly and completely, and carry many suspended contaminants with it.
How do chain drives function?
They transmit torque to the chain drive through a central sprocket.
Why is the chain drive preferable in a grader or skid steer application
Because the final drive housing permits a certain amount of travel and a central pivot, acting as a walking beam system, and allows a considerable amount of ground clearance, as well as the chain drive absorb the shock loads as the tires travel over the obstructions
Why are smaller planetary’s used in articulated trucks ?
They allow for smaller components, reducing weight and allow for higher speeds
The final drive system in tracked equipment are only a double reduction spur gear arrangement. T/F
False, the final drive may consist of a single reduction or double reduction spur gear arrangement or a single reduction, double reduction or even a triple reduction planetary assembly
Which of the following can be used in off-road equipment final drive systems?
any of the above can be used in a final drive system
