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Hayes Lemmerz has made an enormous leap in technology by creating a new “4 in 1” disc rotor that solves brake industry noise, dimension accuracy, thermal diffusivity and “hot spot” rotor problems. By closely adhering to a disciplined system of concurrent planning, product development and production feasibility studies (which included material development and CAE design and dynamometer and vehicle tests), Hayes has solved the brake industry's top four warranty concerns. Development of several propriety manufacturing methods, production system/equipment and quality assurance procedures followed to bring this product from the Development Laboratory to the Production Plants. Hayes' new brake rotor is designed with damped iron composition, 72 curve fin rotor geometry and is then processed using Hayes' patented ULTRA-Q process. The 72 curve fin rotor design, developed through previous Hayes efforts (Ref-1,2,3,4) creates a 100 degrees F cooler running rotor.

Noise, Vibration and Harshness problems in rotors and drums show up in different forms in automotive brakes. The NVH problems may reside either in foundation brakes, apply systems, anti-lock systems or having nothing to do with brake systems but are related to other automotive components such as suspensions, wheel bearings, tire and wheel, drive axle or body structure. The NVH issue is a major warranty cost issue that the car manufacturers and suppliers have to face. Hayes Lemmerz has patented a new rotor design where lowering noise and vibration were the main design criteria. We have used a design concept unique to the brake industry but commonly used to dampen noise. The rotor introduces a sound deadening layer under the brake cheeks. The brake cheeks are attached to brake ribs or fins by a safe and reliable joining method, with the noise damping layer molded on the rear of brake cheeks. We have achieved noise reduction of 50% compared to current production design rotors.

Hayes Lemmerz has patented a straight 42 fin rotor design which has air entry from the inboard and outboard side of the brake rotor. In a previous brake colloquium, we reported that a 5% increase airflow occurs in this design compared to the conventional 100% inboard entry rotor. We have now studied the thermal cooling rate and distortion due to temperature on the dynamometer. The current Hayes Airflow Rotor Design has exhibited 100 degrees F lower peak temperature and 50% less coning when compared to current production rotor design. More work is being done to analytically understand the airflow and thermal distortion of the rotor compared to instrumented vehicle tests like DST (Detroit Suburban Traffic), and LACT (Los Angeles City Traffic).

Hayes Lemmerz, in a previous paper (Ref-1), has introduced an HQ (Hayes Quiet) rotor design where the noise level was reduced by 50%. In this paper, various methods of joining the brake plates to the fins are investigated. The effect of welding is to create a metal joining path which connects the bell shape of the rotor and consequently, the noise level increases. Glue between the brake plates and fins acts as an excellent noise damping layer, but welding through such a layer introduces porosity. The successful design used in the HQ Rotor is when brake plates and long fins are glued together and in place of short fins flat head screws that are used to hold the brake plates against the fin's surfaces. The result of this joint is a Q-Factor number of 211. Damped iron cast joints exhibits a Q-Factor of 500. Glued joints with screws show a Q-Factor of 211 and this kind of joint does not raise the Q-Factor compared to just glued joints.

Hayes Lemmerz has published in previous papers (Ref-1, 2 & 3), the method to low temperature nitride and polymer coat cast iron rotors to provide increased corrosion life, wear resistance and reduction in brake noise. We have, in this paper, investigated the two key dimensions of the rotor before and after the Nitriding Process. Low temperature (1050 degrees F) nitride finish machined rotors have to be handled in a special support fixture to prevent a change in thickness variation (TV) and lateral runout (LRO). Hayes Lemmerz has developed methods to keep LRO and TV in the print specification after the Nitriding and polymer coat process. The parts are made to extremely tight LRO and TV tolerances so that Nitriding done on such rotors, the dimensions of the rotors do not exceed print specification.

Hayes Lemmerz has pursued fin configurations in straight and curved fin rotors to achieve high airflow velocity. The largest increase in airflow velocity of 37.2% is achieved by curving fins to a specific entry and exit angle and increasing surface area by increasing fin number. There is a need for funneling air into the narrow entry in the hub area. The new “Hayes Air Director” successfully channels air into the curved fins. Hayes Lemmerz is in the process of casting rotors with curved fins and the air director idea. Dynamometer and vehicle tests will follow. The current renwood model of the rotor design shows 34.8 to 37.2% increase in airflow velocity when tested on the Hayes Airflow machine.

Hayes Lemmerz has published papers (Ref 1 and 2 ) where different rotor designs were investigated to increase airflow velocity. We also have published the dynamometer test's data to show the 100 degrees F drop in temperature and 50% drop in deformation in rotors with 5% increase in airflow velocity (Ref 3). In the previous paper (Ref 4), the increase of 37.2% of airflow velocity in a 72 curved fin rotor design, was shown. In this paper, we are showing the results of dynamometer testing the 72 curved fin rotor design. When the 72 curve fin rotor design is compared to current production design, the 72 curve fin rotor design shows, a 140° F (60° C) drop in temperature during heating and cooling cycles. Hayes Lemmerz is testing this rotor design on standard vehicle tests ( LACT and DST). The results of these tests would be presented in another paper.