Traction and Stiffness Flashcards
What effect does traction have on center of mass?
Sideways force T.r
Rotating action or moment T.r * h
What is the cornering efficiency?
The loss of relative traction.
Describe the change in weight distribution when going round a corner.
Vertical load on the outside corner increases
Vertical load on the inside corn decreases.
In what ways can car designers increase traction.
Keep all tires on the ground at all times by ensuring as even a load distribution as possible.
How does body stiffness affect the vehicle?
Keeps the tires on the ground at all times
Ensures weight distribution during cornering
What are the two most important types of loading?
Bending
Tortion
Why might bending occur on the body?
Weight of the passengers, engine (static load)
Dynamic effects when driving over imperfections in the road
What is the job of the beam?
To transfer applied loads to the foundations without deflecting too much.
How is a shear load applied?
Zig-zag pattern
Half the load is applies to each support
What force would cause a beam to bend?
Shear load
Tension at the bottom, compression at the top
Fd
Describe the engineer’s theory of bending?
Internal bending forces vary linearly.
Maximum tensile force on only one surface.
Zero force at the neutral surface
Maximum compressive force on the other surface.
How is the new iBeam better?
Makes more use of neutral surface.
Resistance to bending by the flanges (top & bottom)
Give some examples of beam section shapes.
Z I C (or channel) Solid rectangles or circles Hollow rectangles or circles
Describe the beam stiffness equations?
M=k.b*theta
K.b=E*I
How can bending stiffness be enhanced?
Change the material
Change the geometry
Increase the depth
What is the second moment of inertia?
Rotational weight.
Shows how the material is distributed about the neutral axis.
Give an example of different beam stiffnesses (try 2/3)
Citroen 5CV Torpedo:
Low power, low weight
Light chassis
Shallow beam sections
Delorean DMC-12:
Heavy construction
Deep beam thickness
Besm intrudes into the car
Lotus Elan:
Thin sheet, light structure
Deep beam
Weight minimised by cutting holes
How can sheet metal be strengthened?
Corrugating
Folding
Attaching stiffners/ribs
What is tortional stiffness?
Ability of the body to resist twisting.
What are the disadvantages of a low tortional stiffness?
Noisy and uncomfortable ride
Possible loss of tyre contact with the ground
^this mean loss of traction
