assume you are pushing on the break as hard as you can. so you can calculate the

Question

assume you are pushing on the break as hard as you can. so you can calculate the breaking force applied

1) An important part of the design process is to survey others' solutions to a given problem. Sometimes this involves 'reverse engineering', where you work out the numbers for an existing design beginning with a physical artifact. In this case, we are interested in automotive hydraulic brake systems. Your job is to estimate the braking force applied perpendicular to the front brake rotors; i.e. how hard are the front brake pads squeezing onto the front rotors? Perform this estimate for a vehicle you have access to physically, so you can estimate the relevant piston/cylinder sizes, lever arm of the brake pedal, etc. If you are having trouble identifying the relevant hardware in the engine compartment, try uploading some photographs or video to our Piazza site; there are a number of experts in the class who can help you. Supplement these estimates with any specific research you can do online for that make/model of vehicle. Feel free to research typical braking systems online as wel. Don't forget to cite where all of your information comes from. If you can get access to a repair or service manual for your chosen vehicle you will get a lot of useful information! In your reality check/verification section, estimate the quality of your force estimate. Do you think your answer is within 10% of the truth? Within 50%?

Explanation / Answer

The First example came to my mind is where we needed design a Hydraullic Disc Brake system For an All Terrain Vehicle we manufactured during our Engineering for a competition. In That particular competation our vehicle needed to have a braking distance within 12 m when brakes are applied at the speed of 40 KMPH. So In that case we needed to go in reverse direction starting from stopping distance towards Braking effoert applied at the pedal and accordingly choose the intermedeiate system parts.

Braking Distance is,

                          SD = V2 / (2 * d) ...... Where, d- decelaration of vehicle due to braking

12 =123.4321 / (2 * d )

d = 5.14 m/sq.sec

Therefore our vehicle required to have the total decelaration in the above range. From this we will be able to calculate the frictional force required between tyre and surface.

Deceleration Of Vehicle,  

                        d = Ff / mass of Vehicle

5.14 = FF/ 250 ...... mass of our vehicle was 250 kg(with driver)

FF = 1286 N

But Frictional Force At Wheel Is,

                     Ff = µ * Fw ...... Fw- Braking force being applied at the wheel

Fw = 1286/0.6= 2143 N ...... µ=0.6 and it varies with the nature of surface under tyre

Now Braking Torque ,

                      TB =Rolling Radius * Fw= Ff between brake pad and disc *Effictive Radius

0.96R * Fw = µ * Fc * Reff

0.96 * 0.2794 * 2143 = 0.37 * Fc * 0.079 .... we designed a brake disc of Fc = 19670 N Dia=180 mm after many iteration

Since, R= tyre radius = 11 inch

Therefore the clamping force,

Fc= Pressure in calier * Ac* 2n* no. of wheel

19670 = Pc *  0.25 * 262 *4 * 4 ..... the caliper we chose was double cylinder 26 mm dia.

n= no of cylinder

Pc = 2.4 Mpa

Ideally pressure generated in the caliper should be equal to that of master cylinder. but some frictional losses takes place. assuming hydraulic efficiency of 85%

pressure in master cylider is Pm = Pc/=2.4/0.85 = 2.75 MPa

Pressure Generated in Master Cylinder

                      Pm = Fm / Am

2.75 = Fm / 285.02 Master Cylinder Specification : 1. Bore = 19.05 mm

2. Stroke = 20 mm

Fm = 776.23 N

Force Applied on Master Cylinder Piston,

                        Fm = Pedal Effort * Pedal Ratio * 9.81

776 = F * 4 * 9.81

F = 20 kg = 196.2 N

This force shoulde be applied at the pedal.

                          

  

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