The Birmingham age-herald., 1918-04-28

Stopping is the most important function of the motor car from the standpoint of safety, which is the most important standpoint to be considered. If there is anything which should never be taken for granted and yet which universally is taken for grant ed by buyers of passenger cars it is the brakes. Statesmen are called upon to demonstrate every quality that motor car should have but it's simple ability to stop. Acceleration, quietness, ease of riding, economy, accessibility, looks, appointments, ease of starting and so on are the watchwords of the present-day buyer.
 '. How many ask the demonstration to stop his car from 30 miles an hour in less than 30 feet, queries Merrill C.. Horine in Motor Life. "A good car should be able to do so with ease Iii an emergency 1t ought to be able to stop in 20 feet on a level, dry road. To realize what this means consider that an ordinary, medium sized four or light six is about P feet long over all. A normal quick stop should there Aci 70 pC iliduC III c tllIle over three car lengths; an emergency stop in less than two.
 Tt is not enough however, that the car be able to 3too in this space when purchased. It must remain able to do th1s. The number of cars which have seen few months of service whose brokes are below normal effectiveness is alarming. Speed limits have been an utter failure in preventing motor accidents and the reason is plain: The danger of a carelessly or incompetent- ly operated motor car is not in the speed at which it runs but in the distance required to bring it to a halt. car with ineffective brakes is more dangerous at 10 miles an hour than one in proper conditions is at 40
 Tn spite of their importance anu frequent neglect. brakes are one of the simplest clements of the car and one of the easiest parts to take care of and keep, in adjustment. Whether located within the brake drums of the rear wheels. on the outsides of the same drums or outside or inside drum on the driveshaft, the motor car brake is simply a shoe which bears against the revolving drum and de- bends upon just two things for it's ability to stop it's motion These are pressure and coefficient of friction The latter term is engineering slang Tor what practical-tongued people might call cling, It is easier to rub the nail of the finger over this page than the tip because the coefficient' of friction of the tip is greater than that of the nail. Similarly if pressure is brought to bear on the finger. with either nail or tip in contact with the page, the resistance to motion is cor respondingly increased
 The pressure on the brake is nro duced by the mechanism which is ac- tuated by the pedal or lever manipu- lated by the driver. The friction CO., efficient is natural property of tne asbestos-copper fabric with which the shoe is faced, or as more usually ex- pressed, is lined
 On the external brakes this pres sure is applied by contraction of a flexible band of rigid shoes and on in- ternal types by expanding rigid shoes The manual operation of the controls requires that there be great lever age on the brake
 This may multiply the power of the person driving the car several hundred times, so that 50 pounds pressure on the brake pedal becomes 1000. per- haps on the surface of the brake. As the pressure is increased so that if the brake pedal is pushed five inches the brake shoes themselves will move only the fraction of an inob Nou, ;f