0 HACETTEPE UNIVERSITY FACULTY OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING OMU 332 VEHICLE COMPONENT DESIGN PROJECT NO : 2 PROJECT TITLE : NORSTER 600R BRAKE DESIGN GROUP NAME : EGG PREPARED BY : Gökhan YAZAR Gizem ÖZEL Erkin Barış BİLGİ DATE : 07.06.2011
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HACETTEPE UNIVERSITY
FACULTY OF ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
OMU 332
VEHICLE COMPONENT DESIGN
PROJECT NO : 2
PROJECT TITLE : NORSTER 600R BRAKE DESIGN
GROUP NAME : EGG
PREPARED BY : Gökhan YAZAR
Gizem ÖZEL
Erkin Barış BİLGİ
DATE : 07.06.2011
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1. STATEMENT OF THE PROBLEM
The problem is to design a front brake system for Norster 600R according to
following considerations:
- Brake force distribution
- Brake distance
- Max. brake temperature requirements
2. INTRODUCTION
Missions of the front brake system design are given below:
- Selection of friction material
- Foundation brake design
- Heat transfer analysis
At this project, we will design a disc brake for front brake system. To design a disc
brake, we must calculate the following system parameters:
- Number of pistons
- Brake cylinder area
- Brake rotor/Brake pad dimensions
- Lining friction material and friction coefficient
- Brake factors
- Front brake line pressure
After all these calculations, disc brake design will be completed with the heat transfer
analysis.
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BRAKE DESIGN
Required Data
Empty and loaded vehicle weight
Static weight distribution: lightly and fully laden
Wheelbase
Center of gravity height: lightly and fully load
Tire and wheel size
Max. speed
Standards
Steps of Design
Selection of Brake Force Distribution
Hydraulics
Design of Foundation Brake
Pedal Assembly
Disc Brake
Drum Brakes
SCHEDULE
Date Submission 1 Submission 2 Submission 3 Submission 4
13.05.11 Selection of Friction Material
20.05.11
Foundation Brake Design
27.05.11
Heat Transfer Analysis
07.06.11
Technical Drawings
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THEORETICAL KNOWLEDGE
General uses of the brakes can be formulated in terms of three basic functions a
braking system must provide:
1. Decelerate a vehicle including stopping.
2. Maintain vehicle speed during downhill operation.
3. Hold a vehicle stationary on a grade.
Deceleration involves the change of the kinetic and potential energy (if any) of a
vehicle into thermal energy. Important factors a brake design engineer must consider
include braking stability, brake force distribution, tire/road friction utilization, braking while
turning, pedal force modulation, stopping distance, in-stop fade and brake wear.
Maintaining vehicle speed on a hill involves the transfer of potential into thermal
energy. Important considerations are brake temperature, lining fade, brake fluid
vaporization in hydraulic brakes and brake adjustment of air brakes.
Holding a vehicle stationary on a grade with the parking brake is mainly a problem of
force transmission between the application lever and the tire. However, since a parking
brake may be used for vehicle deceleration in an emergency, both thermal and vehicle
dynamic factors must be considered by the design engineer.
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DISC BRAKES
The disc brake is the best brake we have found so far. Disc brakes are used to stop
everything from cars to locomotives and jumbo jets. Disc brakes wear longer, are less
affected by water, are self adjusting, self cleaning, less prone to grabbing or pulling and stop
better than any other system around.
The main components of a disc brake are:
The brake pads
The caliper, which contains a piston
The rotor, which is mounted to the hub
Disc Brake Components
Brake Pads: There are two brake pads on each caliper. They are constructed of a metal
"shoe" with the lining riveted or bonded to it. The pads are mounted in the caliper, one on each
side of the rotor. Brake linings used to be made primarily of asbestos because of its heat
absorbing properties and quiet operation; however, due to health risks, asbestos has been
outlawed, so new materials are now being used.
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Brake pads wear out with use and must be replaced periodically. There are many types and
qualities of pads available. The main differences between these types are brake life (how long
the new pads will last) and noise (how quiet they are when you step on the brake). Harder
linings tend to last longer and stop better under heavy use but they may produce an irritating
squeal when they are applied.
Brake Pads
If the lining wears down until to the metal brake shoe, then there will be a "Metal-to-Metal"
condition where the shoe rubs directly against the rotor causing severe damage and loss of
braking efficiency. Some brake pads come with a "brake warning sensor" that will emit a
squealing noise when the pads are worn to a point where they should be changed. This noise
will usually be heard when your foot is off the brake and disappear when you step on the brake.
If you hear this noise, have your brakes checked as soon as possible.
Calipers: There are two main types of calipers: Floating calipers and fixed calipers. There
are other configurations but these are the most popular. Calipers must be rebuilt or replaced
if they show signs of leaking brake fluid.
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Single piston floating calipers are the most popular and also least costly to manufacture
and service. A floating caliper "floats" or moves in a track in its support so that it can center
itself over the rotor. As you apply brake pressure, the hydraulic fluid pushes in two
directions. It forces the piston against the inner pad which in turn pushes against the rotor. It
also pushes the caliper in the opposite direction against the outer pad, pressing it against the
other side of the rotor. Floating calipers are also available on some vehicles with two pistons
mounted on the same side. Two piston floating calipers are found on more expensive cars
and can provide an improved braking "feel".
Brake Caliper
Four Piston Fixed Calipers are mounted rigidly to the support and are not allowed to
move. Instead, there are two pistons on each side that press the pads against the rotor. Four
piston calipers have a better feel and are more efficient, but are more expensive to produce
and cost more to service. This type of caliper is usually found on more expensive luxury and
high performance cars.
Rotor: The disc rotor is made of iron with highly machined surfaces where the brake
pads contact it. Just as the brake pads wear out over time, the rotor also undergoes some
wear, usually in the form of ridges and groves where the brake pad rubs against it. This wear
pattern exactly matches the wear pattern of the pads as they seat themselves to the rotor.
We decided to use red colored dimensions and values.
-Thermal Considerations, Temperature Rise
m_tot =1.5353e+003
F_f = 4.1151e+003
R_w =265.4400
T_bf =546.1615
T =273.0807
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k =1.1500
V1 =26.3889
m = 1.5353e+003
Eb = 6.1475e+005
ro_disc = 7800
R_disc = 130
t = 30
m_disc =12.4237
Cp =500
delta_T =98.9630
Tamb = 25
t1 = 150
hcr = 53.6000
A =0.2124
W = 12.4237
beta =0.0018
Tmax = 155.2711
Temp_Rise =130.2711
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5. DISCUSSION
This project presents the outline of the front brake design for Norster 600R. It is
concluded that hydraulic brake system in all car are same with little different in components
structure like pad materials and rotor material. The researches on brake pad materials
stated that commercial composition of the pad cannot be concluded whether is preferable
to contain organic or semi metallic brake pads contain more copper. Both organic and semi-
metallic may contain copper although specific amounts will depend on the manufacturer.
Found that contact areas also increase as wear develops. This corresponds to the reduction
of roughness values of the pad surface.
For the dimensions of the brake system components general assumptions are made
according to Brake Design and Safety (R.Limpert).The most important criteria for the rotor
and inherently for the other parts is the rim diameter of the wheel. Reducing the rotor width
and a ventilated design achieve reduce in weight and also improvement of cooling
characteristics.
After the specifications of the dimensions of the brake assembly parts, actuating
force, braking torque, equivalent radius and force location values were calculated and there
is no critical values are observed for the selected material. And then, thermal analysis was
done for the brake system and the maximum temperature rise in case of a hard braking
condition was calculated. Results show that, there is no risk of overheating and possibility of
hazardous condition with respect to material properties.
Finally, engineering drawings were made by using Catia for the parts which were
designed. In engineering drawing, was not entered into details and the other parts such as
bolts, pistons etc. were not shown. Drawings of the main components which are rotor,
caliper and pads were done and general dimensions of the part were indicated in the
drawings.
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6. APPENDIX
Matlab Input Codes
-Total Braking Distance and Maximum Deceleration
tr=1.2; %reaction time ta=0.1; %application time tb=0.18; %deceleration rise vo=95/3.6; %max. velocity dt=120; %total braking distance
dtot=0; dmax=10.0; %dmax(max. deceleration) when total braking distance=120 m
while(dtot<120) d1=vo*(tr+ta); d2=vo*tb-(dmax/6)*(tb^2); d3=(vo^2)/(2*dmax)-vo*tb/2+dmax*(tb^2)/8; dtot=d1+d2+d3; %total braking distance dmax=dmax-0.0001; end
% dmax and corresponding total braking distance dmax dtot
-Actuating Force, Braking Torque, Normal Pressure, Equivalent Radius, Force Location
h_max = 1.4; %[m] Max. Height of the Vehicle(ASSUMPTION) mu = 0.85; %[] Coefficient of Friction Between Tires and Road(ASSUMPTION) g = 9.81; %[m/s^2] Gravitational Coefficient f_r = 0.055; %[] Rolling Resistance Coefficient(ASSUMPTION) i_t_1 = 3.818; %[] First Gear Ratio i_d = 4.412; %[] Differential Ratio NRD=14*24.5; %[mm] Nominal Rim Diameter NSW=175; %[mm] Nominal Section Width PHI=0.60; %[] Aspect Ratio K=0.96; %[] Dimensionless Constant,0.96 for Radial Automobile Tires m_unl = 532; %[kg] Unladen Mass gama = 1.03+0.0016*(i_t_1*i_d)^2; %[] Rotating Mass Factor(ASSUMPTION) m_eq_unl = m_unl*(1+gama); %[] Equivalent Mass m_pass = 80*2; %[kg] Passenger Masw(95%Percentile(ASSUMPTION) v_tank = 32; %[l] Fuel Tank Volume ro_RON95 = 0.7431; %[kg/l] Density of RON95 [THUMMADETSAK] m_fuel_max = v_tank*ro_RON95; %[kg] Fuel Mass (Full Tank)(ASSUMPTION) m_lug = 30; %[kg] Mass of Additional Luggage(ASSUMPTION) m_add = m_pass+m_fuel_max+m_lug; %[kg] Tot.Mass of Add. Factors(ASSUMPTION) m_tot=m_eq_unl+m_add; %[kg] Total Mass i=0.6701; %[] Brake Force Distribution Factor W=m_tot*g; %[N] Weight of the Vehicle-Laden dmax=-4; %[m/s^2] Maximum Deceleration d=-(dmax/g); %[] Dimensionless Deceleration F_f=i*W*d %[N] Front Braking Force THETA=60*pi/180; %[rad] Caliper Angle Difference R_w=K*((NRD/2)+PHI*NSW) %[mm] Tire Rolling Radius
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T_bf=(F_f*R_w/1000)/2 %[Nm] Front Braking Torque T=T_bf/2 %[Nm] Braking Torque on One Side of the Wheel MU=0.40; %[]Coefficient of Friction for Rigid Molded Asbestos Pads
(ASSUMPTION) for 0.31-0.49
for R_r=122.5:2.5:135 %[mm] Rotor Radius for 14 in Rim Diameter R_o=R_r-20 %[mm] Outer Radius of Pad! 20mm(ASSUMPTION) R_i=R_o-35 %[mm] Inner Radius of Pad! 40mm(ASSUMPTION) R_eff=(R_o+R_i)/2 %[mm] Effective Radius F_d=(2*T)/(R_eff/1000) %[N] F=T/(MU*(R_eff/1000)) %[N] Actuating Force P_a=F/(THETA*(R_o-R_i)*R_i) %[MPa] Largest Normal Pressure P_hyd=9000*10^3 %[Pa] Hydraulic Pressure Pis_Num=2 %[] Piston Number Tot_Area=(F/P_hyd)*10^6 %[mm^2] Total Piston Area Pis_Area=Tot_Area/2 %[mm^2] Allowable Piston Area for Ro-Ri=35 mm R_pis=sqrt(Pis_Area/pi) %[mm] Piston Radius end
-Thermal Considerations, Temperature Rise (rest part of the code)
for passenger cars in high gears) V1=95/3.6 %[m/s] Initial Velocity m=m_tot %[kg] Laden Mass of Vehicle Eb=(k*m*V1^2)/2 %[J] Energy Absorbed by Brake ro_disc=7800 %[kg/m^3] Density of Disc Mat.(Steel(Assumption(7750-8050) R_disc=130 %[mm] Radius of Brake Disc (Assumption) t=30 %[mm] Thickness of Brake Disc (Assumption)(Minimum value
of the thickness is 28.1mm for ventilation brakes)
m_disc=ro_disc*pi*R_disc^2*t*10^-9 %[kg] Mass of the Brake Disc Cp=500 %[J/kg*C] Specific Heat Capacity delta_T=Eb/(m_disc*Cp) %[C] Temperature Rise Tamb=25 %[C] Temperature of Ambient
%% Tmax-Tamb=300 %[C] First Assumption for Temperature Rise t1=60^2/24; %[s] Brake was used 24 times per hour (Assumption) hr=27.5; %[W/m^2*C] Radiation Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) hc=7.5; %[W/m^2*C] Convective Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) MAS=12; %[m/s] Mean Air Speed !!!Assumption fv=6; %[] Multiplying Factor(Shigley Figure 16.24b) hcr=hr+fv*hc; %[W/m^2*C] Overall Heat Transfer Coefficient A=4*pi*R_disc^2*10^-6; %[m^2] Lateral Surface Area W=m_disc; %[kg] Mass of the Brake Disc beta=(hcr*A)/(W*Cp); %[1/s] Tmax=Tamb+(delta_T/exp(-beta*t1)); %[C] Maximum Temperature Temp_Rise=Tmax-Tamb; %[C] Calculated Temperature Rise % First Assumption is not valid
%% Tmax-Tamb=143.5295 %[C] Second Assumption for Temperature Rise t1=60^2/24; %[s] Brake was used 24 times per hour (Assumption) hr=12; %[W/m^2*C] Radiation Component of Heat Transfer
Coefficient(Shigley Figure 16.24a)
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hc=7.2; %[W/m^2*C] Convective Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) MAS=12; %[m/s] Mean Air Speed (Assumption)(Shigley Example 16.5) fv=6; %[] Multiplying Factor(Shigley Figure 16.24b) hcr=hr+fv*hc; %[W/m^2*C] Overall Heat Transfer Coefficient A=4*pi*R_disc^2*10^-6; %[m^2] Lateral Surface Area W=m_disc; %[kg] Mass of the Brake Disc beta=(hcr*A)/(W*Cp); %[1/s] Tmax=Tamb+(delta_T/exp(-beta*t1)); %[C] Maximum Temperature Temp_Rise=Tmax-Tamb; %[C] Calculated Temperature Rise %Second Assumption is not valid
%% Tmax-Tamb=131.3444 %[C] Third Assumption for Temperature Rise t1=60^2/24; %[s] Brake was used 24 times per hour(Assumption) hr=11.1; %[W/m^2*C] Radiation Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) hc=7.1; %[W/m^2*C] Convective Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) MAS=12; %[m/s] Mean Air Speed (Assumption)(Shigley Example 16.5) fv=6; %[] Multiplying Factor(Shigley Figure 16.24b) hcr=hr+fv*hc; %[W/m^2*C] Overall Heat Transfer Coefficient A=4*pi*R_disc^2*10^-6; %[m^2] Lateral Surface Area W=m_disc; %[kg] Mass of the Brake Disc beta=(hcr*A)/(W*Cp); %[1/s] Tmax=Tamb+(delta_T/exp(-beta*t1)); %[C] Maximum Temperature Temp_Rise=Tmax-Tamb; %[C] Calculated Temperature Rise %Third Assumption is not valid
%% Tmax-Tamb=130.3379 %[C] Fourth Assumption for Temperature Rise t1=60^2/24 %[s] Brake was used 24 times per hour(Assumption) hr=11; %[W/m^2*C] Radiation Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) hc=7.1; %[W/m^2*C] Convective Component of Heat Transfer
Coefficient(Shigley Figure 16.24a) MAS=12; %[m/s] Mean Air Speed !!!Assumption(Shigley Example 16.5) fv=6; %[] Multiplying Factor(Shigley Figure 16.24b) hcr=hr+fv*hc %[W/m^2*C] Overall Heat Transfer Coefficient A=4*pi*R_disc^2*10^-6 %[m^2] Lateral Surface Area W=m_disc %[kg] Mass of the Brake Disc beta=(hcr*A)/(W*Cp) %[1/s] Tmax=Tamb+(delta_T/exp(-beta*t1)) %[C] Maximum Temperature Temp_Rise=Tmax-Tamb %[C] Calculated Temperature Rise %Fourth Assumption is valid because the assumption and the calculated
temperature rise is close enough to each other. %Actual temperature rise=130.2711