Disc Brake Overview   

More Configurations, More Choices, More Performance                              

The CirCal disc brake design is based on a helical brake pad advance mechanism which may be driven by hydraulic, pneumatic or electric actuation.  CirCal brake technology can be used in automobile, truck, aircraft, industrial and many other braking applications, including self-energizing emergency and safety brakes.

The CirCal disc brake is a scalable mechanical system which can be configured to provide "hydraulic over mechanical", "pneumatic over mechanical" and "electric over mechanical" braking functionality.  The brake's attributes stem from two fundamental design elements - the helical caliper/pressure plate motion, and the circular (annular) brake pads.  

These features enable greater brake torque, better heat dissipation and cooling*, reduced complexity and size, fewer actuators, less weight and lower cost than conventional high performance disc brake systems.

* See: The CirCal Brake's Fade Resisting Properties

1. The helical pad advance motion provides a mechanical advantage which multiplies the clamping force applied to the rotor and generates more brake torque. This can be translated into higher performance brakes or smaller brakes of equal or better performance than conventional caliper disc brakes.

The helical motion enables equal pad pressure over the entire rotor contact area with a minimum of actuators. High performance automobile and motorcycle brake calipers typically have multiple pistons, the lead and trailing pistons being used to ensure even pad wear and eliminate pad taper.  

The brakes used in commercial and military aircraft typically employ a ring of several pistons to apply distributed force on the rotor/stator stack.  The CirCal brake requires only a single actuator (piston) to achieve the same result; additional actuators can be fitted for fail-safe functionality, redundancy or for applying higher forces.  Fewer actuators offer minimized complexity, reduced maintenance, less weight and lower system cost.

Conventional multiple piston aircraft brakes

Four piston automobile brake calipers

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 2. The circular brake pad provides maximum friction surface area. This allows the use of pad materials with substantially higher friction coefficients than conventional brake pads while still providing long lining life. Higher coefficient of friction materials generate higher brake torque which can result in enhanced performance over a conventional brake of the same size, or equivalent performance with a more compact, lighter and lower cost system. 

Pads can comprise a single annular ring or individual pad segments

Since heat generated by braking action is distributed over the entire surface of the circular brake pad the heat is more efficiently transferred to the rotor, and can be dissipated more rapidly through the pad itself.  Because pad wear is reduced a thinner pad, which is more conducive to heat dissipation, may be used.  Uniform heat distribution on the rotor is also likely to reduce the risk of warping the rotor.

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Advantages & Benefits over conventional disc brakes:

a) Due to the helical brake pad advance motion:

1. The helical brake pad advance motion provides equal pad pressure over the entire rotor contact area with a minimum of actuators

2. Fewer actuators offer minimized complexity, reduced weight, less maintenance, lower system cost.

3. The helical brake pad advance motion multiplies mechanical brake pad-to-rotor force.

4. Positive brake disengagement, in certain braking applications, due to the rotor and pad rotating in opposing directions; the brake pad is "spun" away from the rotor when actuation pressure is released.

5. Minimized "pad drag" - return-spring-assisted pad retraction. (Since there is minimal clearance between the pads and the rotor, conventional disc brakes start dragging the instant there is any pressure in the system.)

6. Actuator location is further from, and can be insulated from, the heat generating pad and rotor interface, so that hydraulic piston seals are less prone to heat degradation, and the possibility of brake fluid overheating is reduced.

7. Aircraft-style multiple rotor "heat stack" brakes can be economically adapted for automotive and other applications.

8. A wide rotor is easily accommodated, allowing wide internal vents for improved cooling.

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b) Due to the Circular Brake Pad surface area:

1. Less pad wear than conventional caliper pads due to much greater pad friction surface area.  

Note: A conventional caliper brake pad typically covers an arc of 30°.  The circular (360°) CirCal^TM Brake pad therefore has up to 12X the friction surface area.

2. Greater stopping power (brake torque) with more aggressive (higher coefficient of friction) pad materials, with similar or less wear than pad materials used on conventional caliper disc brakes.

3. Smaller overall size and lower weight than conventional caliper brakes of comparable efficiency and brake torque.

4. The substantially larger pad to rotor surface area allows heat generated by braking action to be distributed over the entire surface of the circular brake pad so that heat is more efficiently transferred to the rotor, and can be dissipated more rapidly through the pad itself. 

5. Thinner brake pads can be used for faster heat transference and heat dissipation due to the lower brake pad wear rate.

6. More efficient rotor design:

• Narrower swept rotor surfaces (outer to inner friction surface depth) can be employed to allow more efficient airflow through the rotor vents, assisting cooling.

• Wider rotors can be employed to allow more efficient vent airflow.