Year: 1869

In recent article on the EFFECT of
Sewing Machines upon Female Health" "
we made statement in regard to the
power required to drive sewing machine,
estimating it as being One-tenth the pow
OF the average human frame The total
power of the human body was estimated
at 4, ,166 &C foot pounds per minute, which
would give for the power required to drive
average sewing machines, according to
our estimate, In round numbers, 416 foot
pounds per minute, or 900 foot pounds
per day of ten hours, equal to 132 cubic
feet of water falling 30 feet.


Our estimate has been criticised as being
evidently too large. 1t was based upon
some rude experiments with an impovised
tanned results which assured us the
ly within bounds


as our estlnate was questioned, We
took the trouble to call upon several man
ufacturers, every one of whom assured us
that our statement must be nearly correct.
1t was, however, only at one establish
ment we could find any positive informa-
ton.


First it takes on an average, one-eighth





other motive power, to run one sewing
machine; three-tourths of the power be
ing lost or wasted in stoppages, in check.
ing the motion of the machine, in running
slow and fast, etc, etc. 1t is from not ap-
preciating the great loss of power arising
from the above causes that most of the
motors invented for this purpose have
proved failures.


When the ordinary treadle motion is
used, if proper adjustments are made, one
thirtysecOnd of horse e-power will do the
work, or little more than one thousand
fOot-pOunds per minute. This makes
the average power required about
One-fOurth of the power of the hu-
man frame. But as many machines
run much lighter than the average,
we are assured that our estimate intended
for the power required for domestic ma
chimes and light sewing, is not far out of
the way, and that it is certainly within
bounds. The figures obtained are based
upon actual experiment


1t Is common error to estimate the
power required to drive small engines en-
tirely too low. We venture to say that
were the generality of mechanics to esti-
mate without test the number of watches
that could be driven by one horse
power, they would be more likely to
make the number double what
would be correct, than to make it less
The cause for this arises from the want of
a proper appreciation of the difference be-
tween the total power of a motor, whether
animal, man or steam engine, that can be
exerted for short time in case of an emer-
gency, and that which it can do continu-
Ously.


A man can run for short space almost
as fast as an average horse. Without
doubt many men can run at the rate of
mile in four minutes for short space
but few men can accomplish four miles an
hour for ten hours. An average man
could probably raise, under favorable cir
cumstances, twelve thousand pounds one
foot high per minute for one or two, or
perhaps five minutes, but put him at con-
tinuOus lifting and he cannot do half
that.


1t takes but little power to move the
treadles of a sewing machine once but to
do it one hundred times minute, or even
sixty times, is another matter; allowing a
small quantity of force only to each half
stroke, computation will show the az
gregate for ten hours to be something con-
misunderstanding american.