General Motors engineers wanted to eliminate the screeching sound produced by brakes. They are now developing a quieter brake technology that would put an end to the source of frustration for many car owners and automotive technicians who want to find a solution for the noise from this otherwise normally functioning brake.
To absorb the vibrations and keep it quiet, this GM-patented design called the Coulomb friction-damped disc brake that features a thin ring of metal embedded in the brake rotor.
It is named after Charles-Augustin de Coulomb, the 18th century physicist who came up with the friction-based damping mechanism. GM will use this quieter brake technology with a corrosion resistant brake technology on over 80% of GM’s U.S. vehicles by model year 2016. This may save customers over $400 in over 10 years.
GM engineers are testing the quieter brake but it’s likely to be offered on several of its cars and trucks within two to three years. What makes the Coulomb damped brake more remarkable is that it enables the brake to just do its job, according to Jim Webster, GM engineering technical expert for rotors. Due to friction in the brakes, they produce a significant amount of noise when the pads are pressed against the flat face of the rotor to slow or stop the vehicle.
The noise from older brakes could mean that the braker pads are now thinner and thus have to be replaced. However, the noise produced by new brakes is usually repulsive, but doesn’t necessarily mean that there is something mechanically wrong with the system. To minimize such noises in current brake systems, sound-absorbing materials are installed in the brake pads, but could also cause the pads to wear down faster.
On the other hand, the Coulomb damped brake takes care of this unpleasant sound by going straight to the rotor, the largest noise source in the brake system. However, it is difficult to soften the noise from the rotor since this component has large unconstrained areas that are free to vibrate. Thus, to create the new brake, engineers at GM created a proprietary manufacturing process that inserts a metal ring into the rotor. This metal ring insert is wrapped in a special coating to prevent it from melding to the rest of the rotor during casting – thereby enabling the insert to remain free to absorb vibrations and to act as a dampener.
Jim Schroth, a group manager in GM’s manufacturing systems research lab, remarked that the Coulomb damped brake creates a bell that doesn’t ring. This bell is gagged by having the special insert absorb the vibrations in the rotor. This innovation should significantly reduce the number of customer complaints -- in the short-run – over unwanted noise. Nevertheless, the Coulomb damped brake could still provide alerts through electronic sensors when the brake pads are worn and have to be replaced.