Clutches Flashcards
What is a clutch?
A mechanical device used to engage and disengage the power transmission smoothly, especially from driving shaft to driven shaft.
What are the x types of clutches?
- Positive contact clutches
- Friction clutches
- Overrunning (one-way) clutches
- Magnetic clutches
- Fluid couplings
- Centrifugal clutches
What are positive contact clutches and where are they used?
Positive clutches are collars with jaws that interlock, one member being rigidly attached to its shaft while the other slides on its shaft.
- High torque transmitting capability, simple parts, longer life, simple design consideration.
Their uses are limited, but have some applications where synchronous drive is required.
What are friction clutches and where are they used?
A friction clutch is a clutch in which the drive is transmitted by the friction between surfaces attached to the driving and driven shafts.
Used in automotive applications.
What are the issues for friction clutch design?
- Clutch operates in dry conditions
- The force necessary to actuate the clutch should not be too large
- The coefficient of friction between contacting members should remain constant
- Wear should be limited in order to provide the longest practical life for the clutch
- Provision should be made for any energy that is converted to heat
What are the 3 types of friction clutches?
- Single disk clutch
- Multiple disk clutch
- Conical disk clutch
What is an over-running clutch and where is it used?
An over-running clutch provides transmission of torque between two shafts when the input is driven in one direction, whilst allowing full slip in the other direction.
For example, a clutch in an engine starter that allows the crank to turn freely when the engine attempts to run.
Push bike.
What are magnetic clutches and what are their properties?
They use a magnetic field to couple rotating components together.
They are smooth, quiet and have a long life (as there is no direct mechanical contact).
What are fluid couplings?
Fluid couplings transmit torques through a fluid, such as oil. Torque is transmitted through drag forces acting between the fluid and the rotating components
What are centrifugal clutches?
Centrifugal clutches engage automatically when the shaft speed exceeds some critical value. Friction elements are forced radially outwards and engage against the inner radius of a mating cylindrical drum.
How many clutches are there within a 5-speed manual gear box?
11 = 1 single disk clutch, 5 cone clutches, 5 positive contact (cone and +ve contact for synchromesh)
What are the assumptions for clutch calculations?
Uniform rate of wear, uniform pressure, local slipping velocity is proportional to radius, wear is proportional to radius (outside wears quicker).
