To lock all four wheels at the driver's command, repeatably, from any speed the car reaches, without fading over an endurance event.
The driver's pedal drives a balance bar between two Tilton 78-series master cylinders, 5/8 in front and 13/16 in rear. The balance bar's position sets front-to-rear pressure split and is trimmed from the cockpit. Pressure travels through hard lines and soft lines to Brembo P2.34 calipers at the front and ISR 22-049 OC/D calipers at the rear, clamping EBC sintered pads onto full-floating 4340 steel rotors. The rotors float on titanium bobbins retained by titanium circlips, which lets the rotor expand and centre itself rather than being constrained by the hat. Motul RBF 660 fluid feeds from two 15 cc Brembo reservoirs mounted on top of the front bulkhead.
Design to wheel lock, then check the driver can reach it. CR26I locks the wheels at 1.84 g, needing 137 lbf pedal force at 1220 psi front and 720 psi rear, with a brake sensitivity of 77 lb/g. The highest deceleration ever recorded on the car is 1.62 g, and repeated braking events sit at 1.48 g, so the system has real margin above what drivers use. Solve the actual failure mode. CR26I's rotor work was driven by cracking and non-uniform pad wear, not by a weight target, and the material change to 4340 was justified by a thermal and static simulation comparison across 6061 aluminium, AISI 420 stainless, Class 40 gray cast iron and 4340 steel. Full floating over semi-floating. Moving from titanium NAS bolts to a titanium circlip made the rotors genuinely full-floating and removed the constraint that was concentrating thermal stress. 1. Set tire loads at the maximum airspeed seen (90 mph): rear 291.60 lbf at max acceleration, front 454.21 lbf under braking, 427.97 lbf cornering. 2. Sweep master cylinder bore combinations against required pedal force and achievable deceleration, then select. 3. Run a transient thermal simulation of the rotor for a single braking event (2.4 s, 260 C initial, 90 W/m^2-K film coefficient, 0.8 emissivity, 25,375 W heat flux front) and import that thermal load into a static structural run (1.84 g deceleration, 12 MPa pad pressure, 707 N-m moment) with cylindrical and frictionless supports. 4. Compare candidate materials on peak and low temperature and on minimum factor of safety. 4340 gave 741.2 C high, 344.5 C low and FoS 3.6438, against Class 40 cast iron at 490.5 C, 256.5 C and FoS 2.1622. 5. Validate with brake rotor temperature sensors on all four corners and compare measured against calculated.
- Address rotor cracking. - Maintain even temperatures throughout the rotor. - Reduce cost. The material change actually saved $47.59 per corner assembly. - Keep required pedal force inside driver capability. - Raise the fluid boiling margin. Motul RBF 660 raised dry boiling point 60 C (265 to 325 C) and wet boiling point 49 C (155 to 204 C).
- Rotor cracking. The driver of the CR26I redesign. - Non-uniform pad wear. - Brake fade. Recent fade may be residual heat rather than a rotor problem, which points at cooling rather than the rotor itself; noted as unresolved. - Thermal analysis without CR22 measured data is theoretical. Rotor temperature sensors were added specifically to close this gap. - Aerodynamic loading in the brake calculation is theoretical and assumes linear downforce and drag. The MATLAB code is being revised to iterate aero loads through the deceleration. - Mesh convergence. ANSYS Student Edition limits element size to 0.001 m, which caps how far the rotor mesh can be refined.
ANSYS transient thermal and static structural, with the thermal result imported as a load. MATLAB brake calculation for master cylinder sizing, pedal force, bias and deceleration. Brake rotor temperature sensors on all four corners for validation. Mesh convergence studies on both rotors and bobbins. Compressive testing of titanium bobbins on a load frame.