4
The man who persists in overloading his car shows up his total ignorance of the laws of mechanics. When an
engineer designs a bridge he makes it a certain number of times stronger than is necessary to carry the greatest load it
will ever be expected to accommodate. This excess strength is termed the factor of safety. Also, when he designs an
automobile to carry, let us say, five passengers, a certain factor of safety is allowed. The bridge is safe from harm for
the reason that the normal conditions are such that it cannot be overloaded, but there is nothing to prevent an owner
from overloading his car if he wills to do so. The surest preventive of this, however, is a strong application of good
common sense.
Another money saver in regard to a car is cleanliness. An accumulation of mud, sand, dust and grease works
harm in many ways. The grit works into many places, causing wear. Into the body joints, the frame joints, the brakes,
the drive shaft, the engine and in fact all over the car. It prevents the discovery of loose bolts and nuts, which, if found
in time, might save a broken part or possibly life or limb. Sometimes an owner even finds that he is losing that respect
for his car without which he does not give it the care it deserves. All this because he has allowed it to become run
down and disreputable looking.
Summing up briefly, if an owner wishes to keep his car out of the repair shop, he should comply with the
following rules:
1.
Lubricate plentifully and systematically.
2.
Use judgment in handling the throttle.
3.
Use the throttle much and brakes little.
4.
Shun making time on rough roads.
5.
Carry the cars, quota of passengers and no more.
6.
Spend a little time each day in cleaning.
A still shorter summary would read like this:
"KNOW YOUR CAR".
A Few suggestions for obtaining good water- and fuel performances on the road might not be amiss. Drive at
a uniform speed, as nearly 18 to 20 miles per hour as possible. Take hills easily. It requires great excess power to
climb grades at high speed. Keep "old style" engines hooked up as much as they will stand without vibrating. The
new engines do this automatically.
Be sure brakes do net drag. To show how much power is lost by dragging brakes, let us suppose a case.
The diameter of the Model "K" wheels is 36 inches. The diameter of the brake drum is 14 inches. Suppose
the brake is dragging, so that it takes thirty-pound pull at the outer circle of the tire to slowly move the wheel when
car is jacked up. This amount has been determined by experiment and is not an unusual occurrence. Sometimes it is
even more. By the law of levers, the radius of the wheel times the pull equals the radius of the brake drum times the
resistance in the opposite direction (which is of course the drag of the brake). Then
18 times 30 equals 7x where x represents the drag.
540 equals 7x.
x equals 77.1 pounds.
Therefore, it would take 77.1 pounds pull at the rim of the brake drum to start wheel to moving, or putting it another
way,
the brake offers resistance of 77.1 pounds at a distance of 7 inches from the center of revolution. Then the
horsepower absorbed can be expressed.
Horsepower equals circumference of brake drum in feet times number of revolutions per minute times
resistance in pounds divided by 33,000.
Circumference of a 14-inch circle equals 3.1416 times 14, equals 43.98 inches.
43.98 inches divided by 12 equals 3.66 feet.
To get the number of revolutions in a mile divide 5280 by the circumference of the wheel which latter is 9.42
feet. The result is 560. Thus, if we are going sixty miles per hour, the wheels will be making 560 revolutions per
minute. At thirty miles per hour, one half of which is 280 revolutions per minute, end at twenty miles per hour, one-
third of which equals l86.6 revolutions per minute. Substituting these values in our horsepower formula and using
186.6 revolutions per minute for twenty miles per hour, we have
Horsepower equals 3.66 times 188.6 times 77.1 divided by 33,000 equals 1.6 HP
