Page Title: Steel Clad Aluminum Brake Rotor Technology

temperatures. The steel cladding also functions as a thermal barrier in some degree to keep the aluminum
underneath cooler. We have the freedom to select different steels for higher friction coefficient but still use
the widely available pads for the cast iron disc brakes. For example, the average friction coefficients of cast
iron and SCA disc brakes are 0.378 and 0.433 respectively measured by the dynamometer comparison
tests. The technical challenge for the SCA disc brake is how to make a very robust steel and aluminum
bond. The SCA brake technology is based on steel and aluminum mechanical interlocking and
metallurgical bonding through a third metal. The SCA disc brake dynamometer failure mode tests showed
that the pads were completely ruined but the SCA disc brake remained its integrity. Slots that assist in
increasing the friction coefficient also relieves the thermal mismatch challenge between steel and aluminum.

Numerous tests have been performed and passed, including the FMVSS-135 certification test and over
100,000 miles of road tests in the past ten years. Most of the road tests were performed on cars by
mounting a SCA front disc brake on one side and a cast iron front disc brake on the other side. When a
hard stop was executed the car tended to veer towards the side mounted with the SCA disc brake. The
temperatures of the aluminum wheel connected with the SCA disc brake were always higher than the
temperatures of the aluminum wheel connected with the cast iron disc brake. The higher wheel
temperature may increase the tire pressure 1-3 psi temporally depending on braking conditions such as
long downhill braking and repeated braking. The SCA disc brake shows the following merits in comparison
with the cast iron disc brake,

● 30% to 50% weight reduction

● Less brake pad drag

● Considerably better gas mileage up to 10%

● Faster heat dissipation and lower braking temperatures

● Greater corrosion resistance

● No heat dissipation degradation due to rusting

●

Approximately

30% less wear on brake pads

● Last over 10 years or 1

0,000 miles

● Shorter stop distance

● Faster car acceleration

● More precise steering due to un-sprung weight reduction

Steel Clad Aluminum Brake

Introduction

Our technology is an innovative automobile brake system which unites the steel clad aluminum (SCA) disc
brake (brake rotor) and the connected aluminum alloy wheel as an integrated brake. The new brake exhibits
many merits over the widely used cast iron disc brake.

Passenger cars are usually installed with two front disc brakes and two rear drum brakes. Nowadays, four
disc brakes have become more and more popular because of their better braking performance. To execute
braking, a pair of pads, one on either side of the disc brake, is pressed onto the surfaces of the brake,
causing friction and slowing the car. One challenge in the design of disc brake is the need to absorb and
dissipate the great amount of heat generated by brake friction.

Disc brakes are structured usually with ventilation channels for better heat dissipation. The braking heat is
absorbed by the material mass between the two rubbing surfaces of each disc. The heat is dissipated, as
the disc spins, through a) air convection on the two rubbing surfaces, b) air convection in ventilation
passageways cast into the disc, and c) heat radiation of the two rubbing surfaces, if the surfaces become
red hot. A high surface temperature reduces a brake pad’s life and friction coefficient dramatically in regular
brake systems, and is therefore highly undesirable.

Disc brakes demonstrate many advantages over drum brakes. However, their major disadvantage is the
potential of incomplete brake pad disengagement (pad drag) after releasing the brake pedal, resulting in
lower gas mileage.

The vented disc brakes are commonly made of cast iron and prone to rust. Over a period of two to five
years, depending on working environment, vented disc brakes may develop severe rust inside the
ventilation channels, blocking air flow and lowering the structure’s integrity. Brake rusting is one of the major
causes of brake repair.

The soaring gasoline price and predictions of future oil shortages have raised the demand for better fuel
efficiency and reducing automobile weight. To further reduce weight, more iron and steel components,
particularly rotating parts, need to be replaced with lighter materials. The brake systems currently in use are
heavy. The disc brakes and drum brakes made of cast iron weigh 10 to 25 lbs each.

Aluminum is an excellent candidate material for the automotive disc brake application. In comparison with the
cast iron disc brake, aluminum could reduce the brake weight by up to 50 percent. Aluminum also has great
corrosion resistance, faster heat dissipation, equivalent strength, and higher ductility. The major technical
barriers preventing the use of aluminum in brake systems include poor wear resistance and inability to
withstand elevated surface temperatures generated during braking. To overcome both barriers requires
enhancement of aluminum surface properties.

Dr. Scott (Xiaodi) Huang invented the SCA brake
technology to solve the above problems. His research
technology utilizes a new design concept in how to store
and dissipate braking heat. The concept is based on the
fact that most passenger cars are using aluminum wheels
instead of steel wheels nowadays. The new concept is to
utilize the aluminum wheel as a part of the brake system.
The aluminum wheel functions as the major braking heat
sink and radiator because it has a much larger volume
and surface area over a disc brake (FIG 1). In addition,
Aluminum also has a much higher thermal conductivity
and a much higher heat capacity, which makes aluminum
an ideal heat sink and radiator material. The greater heat
capacity results in the capability of storing more heat with
less temperature increase.

A typical brake design is to let the disc brake body store
the maximum braking heat produced from one hard stop
without its temperature increase exceed 230°C for
ordinary passenger cars and dissipate the heat as quickly
as possible to make it ready for the next braking. The
SCA disc brake is a solid type in contrary to normal
vented disc brakes. The reason for using a solid disc
brake is that the solid disc brake has larger volume,
therefore it can store more heat. In addition, the solid disc
brake can conduct heat more easily to the connected
aluminum wheel and is readily manufactured.

The SCA brake technology does not over emphasize disc
brake weight reduction. Too much weight reduction
reduces the capability of storing heat, resulting in higher
brake working temperatures. Higher brake temperature
decreases the friction coefficient between the disc and
pads significantly. The lining materials of brake pads are
commonly bonded with an organic binder which limits the
pad's maximum working temperature. Higher brake
working temperatures increase pad wear considerably.

Another key advantage of the SCA brake technology is
the reduction of pad drag. When the brake pedal is
released in the current disc brake systems, the inboard
pad retracts about 0.006" by the distortion return of the
caliper piston rubber seal as illustrated in FIG 2. Although
the caliper can float toward the inboard or outboard, the
outboard pad still maintains contact with the disc brake
slightly in almost all cars causing pad drag. Typically, a
brake pad induces approx 6.65-13.6 Nm torque of
dragging. The pad drag could become more severe after
the rubber seal loses its elasticity as the rubber degrades
under repeated stress and high/low temperature cycles
during its years of service. Further increased pad drag
may be caused by the lateral runout (LRO) of traditional
rotors if it exceeds the specifications. In comparison, the
core of SCA disc brake is made of aluminum. Aluminum
expands much more when subjected to heat due to its
significantly higher thermal expansion coefficient. While
the thermal expansion pushes the inboard and outboard
pads wider apart the subsequent cooling contraction
creates a clearance between the disc brake and the
brake pads (both inboard and outboard) resulting in a
"force free pad return" (FIG 3). This additional pad return
causes no slower or softer brake response.