Pueblo chieftain., 1921-04-10
Mechanical work Is measured

Mechanical work Ia measured in
| 'foot-pounds' and tho foot-pound Ia
tho energy expended when a fcrce of
ono pound acts thru the distance of
one foot For instance. suppose a per-
son takes hold Of grindstone crank.
| that requires pound force to move
it and, in turning it, his hand passes
thru one foot of distance. He has done
one foot-pound of work Now suppose
a person grasps the handle of heav-
ier stone or other piece Of machinery,
that requires a 80 pound force to keep
his hand has traversed 100 feet, as
measured along tho circle thru which
| it moves. He will then have done SO
times 1000 or $4,000, foot-pounds of
work. He may have taken one min
ute. or five minutes or any other
length of time in which to do this
| amount of work. but he has done it.
| II he performs 1t in one minute he
does it five times as fast as If he
| had done it in five minutes, and works
five times as hard. Tho rate at which
he gives out power being five times
| as great, or, in other words. his out
put five times rs large. When the
term power or output is employed 1t
work is being done-the rate at which
| foot-pounds are being expended in
doing something. II $1,000 foot-pounds
of work are applied to machine
within one minute, it is said that the
power expended upon It Is ono horse
on the apparatus which it drives. at
this rate, it Is said to deliver an out
put of ono horsepower. Referring to
| tho above illustration of the person
| turning a crank with a force of %
pounds and whose hand moves a total
distance of 1000 feet, if he accomp-
Iished this work OF $1,000 foot pounds
in exactly one minute he has been
furnishing power at the rate OF one
| horsepower or has bcen doing the
work of a ono horsepower engine. If
he bo imagined to work eycn harder
| than this, using more forco and NOV
ing his hand further within the min
ute. he would develop greater horse
power, which can be computed by null
iplying together the force cxerted. in
pounds, and tho distance in feet. thru
which it is cxerted and dividing the
product by $1,000. Now suppose an
other illustration namely. of grind
stone, with, a. crank exactly one foot
long. that requires n force OF ten
pounds applied at the handle to turn II
and that it is turned around b25 times
in a minute. What IL the horsepower
required to do this? The total distance
circumference OF $50 o'circles. each of
ono foot radius or two feet in diameter.
and this amount to 525 times times
3.142 tthe ratio of a circles circumfer-
|
30, 900 feet. Multiplying this by 10 (thc
forco acting). gives 5000 foot pounds
and dividing by 5000 gives one horse
power. lie is doing mechanical work
at tho rats OF one horsepower. Now
the twisting or turning force required
to maintain a body such as shaft.
in rotation about an axis is known
as "torque" and IL is expressed as tho
force in pounds acting at a distance of
ono foot from the axis of rotation. or
arsrn ,I., fN~t -
just given the force applied was 10
pounds and the length OF tho crank
ono foot, so that the person exerted
5 torGuo of N pounds-fect II the
I crank had been two feet instead of
, ono foot long and tho fcrcc applied
tho same. the torque would have been
10 pounds-fect. Tho torque in pounds
foot being always obtainable by multi
plying tho force applied in pounds by
tho shortest distance from tho axis
, ton. All tho above is for the purpose
OF making clear that tho power pro-
ducinS rate, horsepower or output of
: an engine or any other motive ma
chino is proportional simply TO tho
; force with which It turns multiplied
, by tho speed with which 1t turns or.
in other words to its speed and its
torquo multiplied together. In tho
case of an engine. for instance. if the
horsepower which II is developing and
both known, tho torquo 1t exerts, in
pounds-fect. can always be computed.
1t being only necessary to multiply the
| horsepower by 5c5. and divide the pro-
duct by tho speed in revolution per
! minute. With any other two OF the
} above three quantities known. IL is
! equally easy to obtain the third. The
, above statements arr necessary to the
understanding of engine tcst curves, to
tho explanation OF which the ncxt ar
, ticlc will be devoted.
Relocating storage Battery
| g. A. A. r. asks; Can I change the
location of tho battery on my car from
under tho front seat to under tho roar
seat? Where can | obtain tho longer
cable that would be reguircd2
Answer: II you can find now To-
cation, where tho battery can be Sc
curcly held in an accessible position
and not interfere with any parts of
tho car mechanism. the proposed
change should he practicable. The bat
, terry support should be quite strong