Tread Flashcards
What’s the difference between elastomer deformation and metal deformation
metals deform by altering their bond lattice structure, elastomers don’t alter their bond structure when stretched
What is frequency in terms of tires
rate of compression and expansion cycles
How does Low, Medium and High frequency affect the rubber tire
How does Low, Medium and High temperature affect the rubber tire
draw 2 graphs, modulus against frequency and modulus against temperature of a tire
draw 2 graphs of the Energy loss of a tire agaisnt frequency and temperature
draw a picture of a tire and label Rg, Rh and Rw
how do you calculate the velocity of a tire
whats the formula to calculate rolling radius
explain why the tread is stretched more at the edges of the contact patch then the middle while the car is rolling at constant velocity
Tail moves with Tire’s velocity
Head moves by tangential velocity
at edges the tangential velocity is greater then the tire velocity
in the middle the tire velocity is greater then then tangential velocity
difference in velocity causes stresses that stretch the treads
between Rw and Rg, head moves faster then tail, tread stretches with motion of tire
between Rw and -Rw, tail moves faster then head, tread stretches against motion of tire
draw and explain the stresses within the tread while breaking and accelerating
Breaking , Tail velocity > head velocity
Accelerating , Tail velocity > head velocity
explain slip
Tail moves with Tire’s velocity
Head moves by tangential velocity
Difference in relative velocity between Head and tail is called slip and produces a stress (force) as a result
How do you calculate slip?
What is significant about negative and positive slip.
Explain how bicycle spokes support the weight of the cyclist and the bike
All spokes are under tension
Bottom spokes are compressed
The tension of the bottom spokes decrease
The difference in tension between the top spokes and the bottom counter the load
Bike is hung by the top spokes
Explain how a tire supports the vehicle
Bottom sidewalls of the tire are compressed
this increases the pressure on the top of the tire
The difference in pressure at the top and bottom produce a force upwards
this pulls the bead attaching the tire to the rim
to counteract the load
Draw the X-axis view of a FBD of a tire turning right
which way is the car turning? explain why it is deformed in that way
Lateral force is produced to counteract the inertial centrifugal force
Lateral force pulls the sidewall at varying forces along the tire
what is a slip angle
angle between a rolling wheels actual direction and the direction its pointing
explain self aligning torque
Lateral force doesn’t act perfectly central on the tire, it acts on a point behind the centre due to the slip angle.
There is a lever arm (pneumatic trail) between y axis of the wheel and the lateral force. This leaver arm produces a moment to try and rotate the position of the tire to its actual heading direction.
The torque reduces as lateral force, slip angle and the pneumatic trail decrease
what is tire conicity
where a properly inflated tire causes a car to veer left or right
will this tire veer left or right?
draw a graph of how a tire with conicity lateral force changes with slip angle
what is camber thrust
force generated perpendicular to the travel, due to a camber angle and finite contact patch
draw a graph of how a tire with plysteer lateral force changes with slip angle
what is ply-steer
coupling between different planes of the tire, cause a lateral force
