Week 5 definitions Flashcards
What does an idler gear do?
It allows for reversing by reversing the gear direction in the gearbox
What happens if a gearbox needs more than 6 gears? In what type of vehicles is this usually found?
An additional gearbox is needed, this is usually found in commercial vehicles.
What is usually the lowest gear ratio range for both commercial vehicles and passenger vehicles?
3-4.5 for passenger cars and 5-8 for commercial vehicles
What do more gears result in?
Improved fuel economy, performance,increased complexity and greater mass.
What does increasing lay shaft distance lead to? What is Ka, Temax , G1st and nt in the equation for layshaft distance?
It leads to a reduction in gear stress, which increases gear life. Ka is the application factor, Te max is the maximum engine torque, G1st is the first gear ratio, and nt is the application efficiency.
Gears definition: What is pitch point?
The point where pitch circle diameters interact
Gears definition: What is circular pitch (PC)?
Distance along the pitch circle diameter between teeth.
What is the diametral pitch (PD)?
The number of teeth per mm of diameter of pitch circle
What is the module? What is this equal to?
It is the pitch circle diameter per tooth. Equal to 1/ PD or Pc/pi
What is the pressure angle?
The angle between the tooth face and gear wheel tangent.
Why would you replace spur gears with helical gears?
Due to the high amounts of noise generated with spur gears, helical gears are much quieter.
What is helix angle?
It is the angle between the helix gear and the axis line of the gear.
What is face width?
It is the axial length along gear teeth
What does a higher helix angle lead to?
A reduction in bending strength
What does increasing face width lead to?
Increased strength, but also an increase in gear mass and size.
Name all the parts of the drivetrain.
Engine goes to clutch, goes to gearbox, goes to prop shaft, goes to final drive/ differential goes to drive shaft to wheels.
Why is a clutch needed and what does it do?
When changing gears the engine needs to be disconnected. The clutch disconnects the engine to allow for this.
Why isn’t a dog clutch used?
The engine doesn’t produce high power at low speeds. Therefore the engine needs to be moving, this means that a dog clutch is not viable as it would cause a sudden jolt, as it cannot transmit torque smoothly, hence a friction clutch is used so smooth torque transmission using two plates.
What type of clutch is used in cars?
Friction clutch for smooth torque transmission
What does the prop shaft stand for? What are some important prop shaft properties
Propellor shaft. It needs to have strong resistance to the twisting action of the driving torque. It must not sag under its own weight- if the center of mass is not aligned with the center of rotation, vibrations will occur.
Why is a tubular prop shaft often preferred?
Due to the lower weight, Higher resistance to misalignment, Good torsional strength, and lower inertia.
What are composite prop shafts used for?
Often reserved for motorsport due to their high costs.
What does the drive shaft do?
It transmits torque from the final drive/ differential to the wheels.
What is the significance of universal/ CV joints?
They allow torque to be transmitted through varying angles, so shafts and joints do not have to be in perfect alignment.
