When were emergency brakes invented?

Answer 1

The emergency brake dates back to somewhere near 1904. (That's an estimate. My grandmother's family bought cars frequently and mentioned that as the first one with an emergency brake.) The early braking systems were push-rod linkages under the vehicle and prone to failure when struck by debris. A cable drawn brake actuator was a suitable backup device for emergency use, although never efficient or durable enough for standard service. They became mandatory in the 1920's in a wave of state laws passed following a number of spectacular and well publicized truck wrecks. (For those thinking proactively, in those days trucks had chain drives and no one had synchro-mesh transmissions. Down-shifting a truck to get engine braking for a run-away often snapped the chain.)

The adoption of dual diagonal hydraulic brake systems in the 1930's made the cable drawn all-wheel emergency brake obsolete - in the event of a failure even one diagonal hydraulic circuit applies more brake effect than the cable actuator can supply to all 4 wheels. Although the cable brake became a useless relic 75 years ago, no politician ever won an election by voting to eliminate anything associated with the words "emergency" or "safety". While vehicles are still required to have an "emergency brake" the required performance of the device, buried in the details of legislation, reflects its status as the useless relic of a bygone era.

The parking brake in your car is attached to the *rear* wheels, not the from wheels where the weight goes when you apply the brakes. Even if the parking brake had enough leverage to lock the rear wheels at highway speed, the braking effect would be alarmingly underwhelming, and it doesn't even have that. (try yours sometime, by yourself, on a rural road at 45MPH). For cars with 4 wheel disk bakes, the "emergency brake" is a mo-ped size drum brake set unto the rear rotor. Most drum in rotor parking brakes are caked in rust and totally ineffective as emergency brakes for a several hundred yards as the rust scrapes off. On vehicles with rear drum brakes, the cable expands the end of the brake shoe ignored by the hydraulic cylinder, but it is the service brake, and its probably not rust choked.

The device is also rarely, if ever used as a parking brake. (The 100 or so cars that park on Telegraph Hill in San Francisco notwithstanding) It usually doesn't have enough drag to keep the car from rolling down a steep hill. In an automatic transmission the transmission pawl in "Park" is much more effective. In a car with a standard transmission, you leave the car in 1st or reverse with the wheels pointed at the curb, set the parking brake, and learn to park somewhere flat next time. (on a steep hill, the car will slowly creep and when you return the car will be either jammed into the curb or be climbing the curb, or have climbed the curb.)