Contemporary braking systems and brake assist technologies showcase remarkable advancements. Manufacturers engage in fierce competition to deliver optimal and comfortable braking solutions. Nevertheless, the journey to attain these current engineering marvels was extensive.
In the beginning…
The undeniable significance of brakes in modern automobiles is widely recognized. Today, the braking system stands out as one of the most crucial components of a vehicle. However, the pivotal role of brakes wasn’t always apparent. During the early days of the automotive industry, inventors primarily focused on propulsion rather than deceleration. Basic mechanisms, combined with internal resistance, served as rudimentary braking systems. Initially, automobiles relied on simple methods such as levers pressing wooden pads against the wheel rim, similar to carriage braking systems, reflecting their design similarities.
As vehicles evolved and speeds increased, it became evident that these makeshift brakes were insufficient. Wooden pads deteriorated quickly and lacked the necessary stopping power, particularly on steep terrain. Consequently, there arose a demand for more effective braking solutions capable of converting kinetic energy into thermal energy efficiently. Various experiments ensued, aiming to enhance braking performance. Improved linings, including copper variants, were introduced to bolster friction force. However, these advancements were accompanied by a notable drawback – excessive noise when in contact with metallic wheels. To address this issue, softer friction materials such as asbestos, cotton, or rubber were utilized. Despite these advancements, early braking systems sufficed due to the limited speeds at which cars operated.
Tyres enter the ring…
The evolution of brakes has been significantly shaped by the advent of pneumatic tires. While offering improved comfort on rough terrain and enabling higher speeds, they posed a challenge for the primitive braking systems of the time. Unlike bicycles, where a pad directly pressed against a tire could suffice, such a solution proved inadequate for heavier automobiles. Consequently, a new form of brake emerged, one integrated within the wheel. Surprisingly, both the drum brake and the disc brake were conceptualized around the same era.
The inception of the first disc brake dates back to 1902, credited to Frederic Wilhelm Lanchester, an English engineer, while Louis Renault patented the drum brake in the same year. Although engineers like Gottlieb Daimler and Wilhelm Maybach had also experimented with drum brakes, it was Renault’s design that gained prominence. Departing from the traditional cast iron drum encased in ropes, Renault introduced a more effective approach, employing brake shoes that pressed against the drum. This brake design has endured to this day, albeit with numerous refinements and adaptations.
Cables to hydraulics
The earliest car brakes operated entirely through mechanical means, relying solely on the driver’s physical strength. Initially, brakes were only fitted to the rear wheels, with the concept of four-wheel brakes not materializing until 1909, largely due to limited engineering knowledge hindering the development of brakes capable of ensuring vehicle stability. Coordinating the operation of four pairs of brake shoes using steel lines presented a significant challenge.
A pivotal advancement occurred in 1917 when Malcolm Loughead, later known as Lockheed, patented hydraulic brakes. Although the concept of hydraulic brakes was initially introduced by Hugo Meyer of Germany in 1895, it failed to gain traction until Lockheed’s innovation. These brakes marked the first mass-produced hydraulic brake system. The introduction of hydraulic fluid brought about significant changes. Firstly, it enhanced braking power. Secondly, it resolved issues such as cable cracking and loosening, making brakes more user-friendly. While early hydraulic brakes were prone to leaks, they offered greater reliability compared to mechanical counterparts.
Further enhancements emerged in 1928 with the introduction of brake assist. A brake servo utilized negative pressure generated within the inlet system to augment braking force. Upon depressing the brake pedal, activation of the master cylinder and a valve released negative pressure from the intake manifold. The pressure differential across the membrane generated an additional force that bolstered the master cylinder piston, directly correlating with the degree of pedal depression. This innovation empowered drivers to effortlessly modulate braking force. As braking systems continued to evolve, vehicles gained the capability to achieve increasingly higher speeds.
Decline of the drum brake
For many years, drum brakes held sway in the automotive industry, enduring even today in some smaller, less potent vehicles such as town cars, typically found on the rear axle. Their prevalence can be attributed to happenstance rather than inherent inefficiency. Despite misconceptions, drum brakes exhibit resilience across diverse road conditions, yet they grapple with high temperatures.
The enclosed nature of drum brakes poses challenges in dissipating heat effectively. Expansion of brake shoes necessitates considerable force and the use of large, heavy drums. Moreover, drum brakes are prone to faults. Despite their simplistic design and enclosed housing, they frequently encounter issues such as shoe jamming, leading to brake overheating and sudden loss of braking force, culminating in hazardous scenarios. Thankfully, the advent of disc brakes provided a solution.
How does the disc brake work
Similar to numerous groundbreaking innovations, the inception of modern disc brakes took place in the realm of sports. In 1993, a Jaguar XK equipped with four Dunlop disc brakes emerged victorious in the 24-hour Le Mans race, marking the onset of a braking system revolution.
Unlike the copper brake linings utilized in 1902, contemporary pads offer improved longevity and reduced squeaking. Subsequent advancements introduced more sophisticated friction linings, including ceramics, semi-metallic blends, or Kevlar, while the use of asbestos, linked to cancer, was phased out. All brake pads leverage the inherent advantages of disc brakes, notably heightened efficiency even under dynamic driving conditions.
Central to the superiority of disc brakes is their ability to dissipate heat efficiently. They rely on air circulation, heat transfer to the rims, and may incorporate specialized ventilation apertures. Ideally suited for mountainous terrain, dynamic driving, and emergency braking scenarios, disc brakes function by exerting pressure on the friction lining and, consequently, on the brake disc. Moreover, they seamlessly integrate with driver assistance systems such as ABS or ESP. In contrast to pushing mechanisms, squeezing proves to be a more effective braking method, with callipers superseding shoes in this regard.
What the future holds
Continual research and development endeavors persist in the quest for ever more efficient braking systems. These systems undergo ongoing evolution concerning both materials and design. A growing number of manufacturers are adopting the practice of “scorching,” wherein brake pad surfaces undergo brief heating to temperatures ranging from 600 to 800 °C. This process aims to enhance resistance to fading, a phenomenon characterized by diminished lining efficiency due to elevated temperatures. Moreover, manufacturers are increasingly prioritizing the reduction of vibrations and squeaks, with premium-quality pads featuring interlayers designed to mitigate such disturbances.
It appears that braking systems may soon encounter reduced demand compared to current standards. The emergence of hybrid and electric vehicles is propelling energy recovery systems as a viable alternative to traditional brakes. Systems akin to those utilized in Formula 1 cars are gaining popularity, wherein energy generated during braking is no longer dissipated as heat but instead converted into electrical energy. While energy recovery systems cannot entirely supplant conventional disc brakes nor suffice for rigorous braking scenarios, they hold promise in mitigating wear and tear on brake discs and pads during routine, everyday driving. The validity of these projections remains subject to empirical validation in the near future.
