Week 8-braking

Question 1

What is Fxf and Fxr?What is Rxf and Rxr?

Answer 1

They are braking forces and rolling resistance forces. If they are in acceleration then they are traction forces (Fx)

Question 2

What is the free-body diagram and equation for braking?

Answer 2

Max = -Fxf - Fxr - Rxf- Rxr - Fd - Mgsin(angle)

Question 3

Draw the free body diagram for static loads as well as dynamic braking

Answer 3

N/A

Question 4

What is the equation for slip, and when is slip occurring in the tires?

Answer 4

(wRe -Vx)/Vx = -1(for full slippage), or 0 for pure rolling

Question 5

Deduce the equations for Fxf max and Fxr max for dynamic braking . Use ax = (Fxf max - Fxr )/m

Answer 5

Answer on PowerPoint

Question 6

How can the equations for Fxr max and Fxf max be used in the graph of y against x, explain and explain what they show towards the locking of tires.

Answer 6

N/a - Power point if unsure

Question 7

what are the typical components of a braking system?Draw it

Answer 7

Master cylinder, Brake hose, Parking brake, Brake pedel, booster

Question 8

What does the brake pedal do in a braking system?

Answer 8

Transmits the foot force into a force producing hydraulic brake pressure

Question 9

What does the booster do in a braking system?

Answer 9

It amplifies the force from the brake pedal to increase the pressure

Question 10

What does the master cylinder do in a braking system?

Answer 10

It converts the force from the booster into hydraulic pressure to brakes.

Question 11

What does the brake hose do?

Answer 11

Allows pressure to flow from the master cylinder to the brakes

Question 12

What does the parking brake do?

Answer 12

It uses mechanical linkage to apply the brakes for parking or during an emergency

Question 13

What is the equation for clamping force?

Answer 13

R = pAE, where p is the pressure in the cylinder, A is the piston area, E is the clamping force efficiency.

Question 14

What are the equations for brake torque at one wheel and the brake force produced by two wheels?What about the force for four wheels?

Answer 14

Tb = 2 up PAr, where uP is the friction coefficient between the brake pad and the wheel, 2 is due to 2 pads on the wheel . The force produced by two wheels is 4 up P A r/ rw.

Question 15

What is brake proportioning?

Answer 15

This is balancing front and rear brake pressure to prevent lock up, tries to lock up both axles simultaneously

Question 16

What is electronic brake distribution?

Answer 16

This is a system that uses load sensors on each wheel to automatically proportion out brake pressure including adapting for passengers.

Question 17

What are the main components of an anti-lock braking system?

Answer 17

Wheel speed sensor, ECU, Solenoid, accumulator, pump

Question 18

What does the wheel speed sensor do in abs?

Answer 18

It measures wheel speed and signals lock up

Question 19

What does the ECU do in abs?

Answer 19

It sends current to the solenoid to magnetise it and affect the opening and closing of valves.

Question 20

What does the solenoid do in abs?

Answer 20

It is for applying and reapplying pressure in the brakes through the opening and closing of valves and an electric current.

Question 21

What does the accumulator do in abs?

Answer 21

It ensures the availability of fluid supply

Question 22

What doe the pump do in abs?

Answer 22

It helps to maintain the required pressure

Question 23

Describe the 6 steps in an abs system.

Answer 23

1- brakes applied at foot pedel, pressure fluid flows through master cylinder to brakes. This allowed until system sees lock up due to panic braking.
2- ECU sends current to the solenoid to magnetise it
3- ABS HOLD- current pulls the first valve up which maintains pressure at brakes
4- ABS RELEASE- current is increased, opening the second valve, which releases pressure from the brake system. This pressure flows to the accumulator which stores it
5- The pump is turned on, returning fluid back to the master cylinder.
6- ABS REAPPLY- abs can now be reapplied and then cylcle repeated