So Powerful that it can Pick Up Bowling Balls
The power of a vacuum cleaner motor is one of the most
misrepresented and misunderstood aspects of vacuum cleaner
technology. This confusion has been accentuated by many
manufacturers and salespersons in their attempt to make their
products appear superior to others. At times this takes the form
of performing amazing demonstrations of the vacuum cleaner's
abilities. Often, when analyzed with a few basic laws of physics
in mind, these amazing feats prove very little and are relatively
meaningless!
The ability of a vacuum cleaner to pick up a 16 pound bowling
ball seems to be quite impressive, especially if done by a small
portable vacuum cleaner. For many years you've seen this demonstrated
on TV. Now there is an even smaller vacuum which can pick up two
16 pound bowling balls at the same time! Should you be impressed?
I actually cringe when I see these misleading promotions especially
since we are so careful to represent our vacuum cleaners in an honest
and straight forward manner.
The laws of physics behind this feat are rather simple. As
explained in our article on the
Fan or Impeller, a partial
vacuum (area of reduced air pressure)
is produced by the spinning fan.
The difference in pressure between the normal atmospheric pressure
and the reduced air pressure in the fan is what normally causes air
to flow toward the fan. If air flow is prevented, the air pressure
within the vacuum cleaner, hose, etc. drops to the same pressure as
at the fan. It is the force exerted by this difference between
normal and reduced air pressure which prevents the bowling ball
from falling. This force is proportional to the area upon which it
is applied as described below.
The unit of measurement for pressure is often stated as force
per area as in "pounds per square inch", etc. An alternate
expression of pressure or pressure difference is to state how high
in a tube a liquid of known weight is pushed or pulled. Examples
of this are the barometer (calibrated in millimeters of mercury or
millibars of pressure) for measuring atmospheric pressure and the
sealed suction gauge (calibrated in
inches of water lift) for measuring
the suction (difference in air pressure mentioned above) of a
vacuum cleaner.
One cubic inch of water weighs 0.036 pounds so the pressure
difference (sealed suction) for a vacuum cleaner which measures 100"
of water lift on a suction gauge is 3.6 pounds per square inch. A bit
of math shows us that the Oreck Buster B vacuum cleaner with about
65" of water lift would exert around 2.3 pounds per square inch on the
bowling ball. An inverted funnel is used between the hose and the
bowling ball to give aproximately 20 square inches of area so the force
exerted to keep a 16 pound bowling ball from falling is over 45
pounds. Since the force exerted is proportional to the area, even
more impressive demonstrations can be done as explained in our
article titled
"So Powerful that it can Lift an Adult Person."
As you can see, it really isn't such a marvel that the small
Oreck vacuum cleaner can hold such a heavy object. To learn about
various methods for rating vacuum cleaner motors, see our article
about the Power of the Suction Motor.
There are many important performance aspects of a vacuum
cleaner system which you can read about in our article on
Identifying Good Performance Factors. These
include the Power of the Suction Motor,
Effects of Brushing Action,
effect of internal resistance
on the Air Flow through the System,
as well as the Efficiency of Paper Bags and
Filtration Efficiency - HEPA, ULPA, etc.
To choose a durable vacuum cleaner which will meet your cleaning tasks and
preferences, see our articles on
Identifying Durable Designs & Construction
and Match Your Tasks and Cleaning Style. A
good, knowledgeable sales person like those at Ristenbatt Vacuum
Cleaner Service can help you determine which vacuum cleaner system
will be the best for you in your particular cleaning situation.
