INTRODUCTION TO WHEELED VEHICLE BRAKING SYSTEMS
Up to this point, each one of our subcourses has covered all the
things that were needed to make a vehicle go forward and backward.
We now know that an operator has controls to make this equipment go
fast or slow; to the right or left; through mud, snow, sand; and on
level roads. But what does the operator do if a child runs out in
front of this moving vehicle, or when traveling on a road a point is
reached where a bridge is washed out? The answer is that the
operator must have one or more controls that will bring the vehicle
to a stop rapidly and with a small amount of effort. The braking
system provides these controls.
Braking is the use of friction to slow a vehicle, bring it to a halt,
or hold it in a standing position. A brake is a device that is
secured to the vehicle axle housings, which do not rotate, and is
used to slow down or hold the wheels, which do rotate. When the
rotating parts are brought in contact with the nonrotating parts, the
friction caused by the rubbing creates the braking action.
All vehicles must be built so they meet the minimum braking
requirements. For many years it has been a set standard that a
braking system must be able to stop a vehicle traveling 20 miles per
hour (MPH) within 30 feet. You must remember, however, this does not
mean the vehicle will always stop in 30 feet. It does mean that if
the tires could get enough traction on the road, the brakes must hold
well enough to stop it in that distance. To get an idea of how much
power is involved in braking systems, imagine a 10,000pound truck
traveling 50 MPH being braked at the rate discussed above. The
energy required to do the braking would be equivalent to 500
horsepower (HP). This is much more than the vehicle engine could
ever produce. Most of the braking systems on modern passenger cars
can handle about eight times the power developed by the engine.
This subcourse is designed to provide you with a knowledge of how
braking system components operate.