Clutches And Transmissons Flashcards
What is Viscous Drag
A shearing action between two moving surfaces
What are three concerns of Viscous Drag
- Make transmission shifts difficult or impossible
- Make shifts rough in a power shift
- Cause safety concerns in a PTO
What are three different configurations of Wet clutches?
- Hydroliclly applied, Spring Released
- Spring applied , hydroliclly released
- Hydrolically operated, Mechanically applied
Hydraulic Clutch components are ?
Inner Hub Friction Plates or Discs Separator plates,an end plate Drum Piston and seals Piston return spring
What is the Pressure regulating valve in most systems set between ?
100-300 psi
What are Three basic types of PTO’s
Transmission driven
Continuous running
Independent
What is viscous drag
The shearing action between 2 moving surfaces
What components make up a Hydrolic clutch x6
Inner hub Friction discs and plates Seperator and end plates Drum Piston and seals Piston return spring
What is a Disadvantage of a wet clutch and why?
It needs 2 oil sources , pressure and lube and can cause lots of heat
What is the purpose of a PTO brake?
To prevent viscous drag for rotating the PTO shaft when the unit is not being used. It is not meant to slow down equipment with high inertial loads. These should be spooled down with the engine before being disengaged.
What are three negative effects of viscous drag?
1)makes shifts in transmission rough or impossible. 2)turns outputs when not engaged. 3)rough powershift activation.
What is the function of a lube cut off valve?
It prevents lubrication oil from entering a clutch pack so that it will not be effected by viscous drag when a function such as a shift is being performed.
How does a transmission brake negate viscous drag?
It is applied by pressurized oil when the clutch pedal is deppressed and stops the transmission input shaft from turning
What are the three configurations of hydraulic clutches?
spring applied/hydraulic release, hydraulic applied/spring release, hydraulically actuated mechanically applied
What are some functions of hydraulically activated spring released clutches?
main traction clutch, powershift clutch, pto clutch
What are some functions of a spring applied hydraulically released clutch?
parking brake, MFD
What are some functions of a hydraulically actuated mechanically applied clutch?
Main traction clutch.
Why is a spring apllied hydraulically released clutch used on MFD circuits?
Because it acts as part of the braking system in the event that hydraulic pressure is lost the braking stability of the unit is not effected.
What factors influence the engagement force of a hydraulic clutch?
surface area of clutch, pressure of oil
What is the function of the hub in a hydraulic clutch?
provides a splined connection to the friction discs and commonly ditributes lubrication oil.
What is the function of the drum in a hydraulic clutch?
splined to the seperator plates and provides passage and commonly the distrobution seals for the presurized activation oil
What is the function of the friction disc in a hydraulic clutch?
provide the a friction surface to allow the engagement of the clutch. Hold a engagement surface material that is capable of holding oil and heat to prevent the friction surface from breaking down.
What is the function of seperator plates in a hydraulic clutch?
They provide the second friction suraface required to engage the clutch.
What effect does doubling the number of plates have on the torque capacity of the clutch?
it doubles the torque capacity
What factors effect the overall torque capacity of a clutch pack
1) oil pressure. 2) piston size. 3) release spring force acting against the piston. 4) coefficient of facing material friction. 5) size of plates. 6) number of plates
What is the dfference between a pressure regulating valve and a pressure reducing valve?
a pressure regulating valve is normally closed while a pressure reducing valve is normally open.
What is the common pressure range of hrdraulic clutch activation pressure?
100-300psi
What are four common modulation devices?
oriface, accumulator, modulation valve, electronic modulation valve.
What is the limitation of an oriface as a modulation device
it only controlls the flow of the oil and not the pressure. Therfore when the plates make contact the engagement can still be harsh. It is often used in addition to other forms of modulation
What is the function of an accumulator as a modulation device?
It controls the rate of pressure rise within the clutch allowing the clutch to engage at a slower rate
What are the two types of accumulators normally found on hydraulic clutches?
Spring or nitrogen
What does a modulation valve balance?
hydraulic force with spring force
an electrohydraulic PWM valve with 200psi of available pressure is activated to 50% duty cycle. What is the output pressure of the valve?
100psi
When a hydraulic clutch’s seals are dissasembled should new seals be installed?
yes
When installing new seals in a hydraulic clutch what is important to check before reassembly?
That the sealing surface on the drum is not worn out.
What are the three configurations of pto’s
transmission driven, continuous running, independent
in a transmission driven PTO what must happen to operate the pto while stationary?
The unit must be in nuetral with the clutch pedal released.
How is the continous running PTO clutch system set up?
There is a two stage clutch that drives the transmission and the PTO. When the clutch pedal is fully deppressed both functions stop. Half way depressed and the pto engages. Fully engaged and both the transmission and the PTO are driven.
When does the PTO input shaft rotate on an independent PTO?
Any time the engine is running.
What are the three available PTO shaft sizes and their spline numbers?
540 1 3/8” with 6 splines. 1000 1 3/8” with 21 splines. 1000 1 3/4” with 20 splines. The 1 3/8” are fro 150HP and below and the 1 3/4” covers everything else.
What are the three common locations for a PTO clutch?
In the flywheel compartment. In the transmission, in a modualar case in the rear of the unit
