Week 8-braking Flashcards
What is Fxf and Fxr?What is Rxf and Rxr?
They are braking forces and rolling resistance forces. If they are in acceleration then they are traction forces (Fx)
What is the free-body diagram and equation for braking?
Max = -Fxf - Fxr - Rxf- Rxr - Fd - Mgsin(angle)
Draw the free body diagram for static loads as well as dynamic braking
N/A
What is the equation for slip, and when is slip occurring in the tires?
(wRe -Vx)/Vx = -1(for full slippage), or 0 for pure rolling
Deduce the equations for Fxf max and Fxr max for dynamic braking . Use ax = (Fxf max - Fxr )/m
Answer on PowerPoint
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.
N/a - Power point if unsure
what are the typical components of a braking system?Draw it
Master cylinder, Brake hose, Parking brake, Brake pedel, booster
What does the brake pedal do in a braking system?
Transmits the foot force into a force producing hydraulic brake pressure
What does the booster do in a braking system?
It amplifies the force from the brake pedal to increase the pressure
What does the master cylinder do in a braking system?
It converts the force from the booster into hydraulic pressure to brakes.
What does the brake hose do?
Allows pressure to flow from the master cylinder to the brakes
What does the parking brake do?
It uses mechanical linkage to apply the brakes for parking or during an emergency
What is the equation for clamping force?
R = pAE, where p is the pressure in the cylinder, A is the piston area, E is the clamping force efficiency.
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?
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.
What is brake proportioning?
This is balancing front and rear brake pressure to prevent lock up, tries to lock up both axles simultaneously
What is electronic brake distribution?
This is a system that uses load sensors on each wheel to automatically proportion out brake pressure including adapting for passengers.
What are the main components of an anti-lock braking system?
Wheel speed sensor, ECU, Solenoid, accumulator, pump
What does the wheel speed sensor do in abs?
It measures wheel speed and signals lock up
What does the ECU do in abs?
It sends current to the solenoid to magnetise it and affect the opening and closing of valves.
What does the solenoid do in abs?
It is for applying and reapplying pressure in the brakes through the opening and closing of valves and an electric current.
What does the accumulator do in abs?
It ensures the availability of fluid supply
What doe the pump do in abs?
It helps to maintain the required pressure
Describe the 6 steps in an abs system.
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
