Tread

Question 1

What’s the difference between elastomer deformation and metal deformation

Answer 1

metals deform by altering their bond lattice structure, elastomers don’t alter their bond structure when stretched

Question 2

What is frequency in terms of tires

Answer 2

rate of compression and expansion cycles

Question 3

How does Low, Medium and High frequency affect the rubber tire

Question 4

How does Low, Medium and High temperature affect the rubber tire

Question 5

draw 2 graphs, modulus against frequency and modulus against temperature of a tire

Question 6

draw 2 graphs of the Energy loss of a tire agaisnt frequency and temperature

Question 7

draw a picture of a tire and label Rg, Rh and Rw

Question 8

how do you calculate the velocity of a tire

Question 9

whats the formula to calculate rolling radius

Question 10

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

Answer 10

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

Question 11

draw and explain the stresses within the tread while breaking and accelerating

Answer 11

Breaking , Tail velocity > head velocity
Accelerating , Tail velocity > head velocity

Question 12

explain slip

Answer 12

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

Question 13

How do you calculate slip?
What is significant about negative and positive slip.

Question 14

Explain how bicycle spokes support the weight of the cyclist and the bike

Answer 14

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

Question 15

Explain how a tire supports the vehicle

Answer 15

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

Question 16

Draw the X-axis view of a FBD of a tire turning right

Question 17

which way is the car turning? explain why it is deformed in that way

Answer 17

Lateral force is produced to counteract the inertial centrifugal force
Lateral force pulls the sidewall at varying forces along the tire

Question 18

what is a slip angle

Answer 18

angle between a rolling wheels actual direction and the direction its pointing

Question 19

explain self aligning torque

Answer 19

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

Question 20

what is tire conicity

Answer 20

where a properly inflated tire causes a car to veer left or right

Question 21

will this tire veer left or right?

Question 22

draw a graph of how a tire with conicity lateral force changes with slip angle

Question 23

what is camber thrust

Answer 23

force generated perpendicular to the travel, due to a camber angle and finite contact patch

Question 24

draw a graph of how a tire with plysteer lateral force changes with slip angle

Question 25

what is ply-steer

Answer 25

coupling between different planes of the tire, cause a lateral force