On Tue, 02 Apr 2013 01:38:59 -0400, Ed Huntress wrote:
On Tue, 02 Apr 2013 05:32:10 GMT, "Harold & Susan Vordos"
wrote:


wrote in message
. ..
On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.

We have a Vacuflow 960--twin motors, with the unit capable of handling
18,000 square feet of building.

Length of the tubing most assuredly makes a difference. The vacuum cleaner
is located in the shop, with tubing extended (underground) to the
house--with the longest runs likely near 100'. There's an obvious
difference of performance in the house as opposed to in the shop. 2"
inside diameter pipe, if you have a question on size.

The rules of physics dictate that there will be losses.

Harold

What Clare is saying, I believe, is that the length of the hose
makes no difference in the value of suction -- if there is no
airflow through the hose. If you hook up a vacuum pump to, say, a
bell jar or to a perfectly sealed vacuum-cure rig for composites, it
doesn't matter how long the hose is. The vacuum will be the same.

What reduces the vacuum is the drag experienced by airflow through
the hose. Longer hoses will measure the same vacuum at their ends,
no matter how long the hose, if there is no flow. But if there is
flow, the more there is, and the greater the inherent drag in the
hose, the lower will be the measured vacuum at the end.

Rules of physics.

So... the implication is that "performance" here implies "time", much
like charging a capacitor. Hooking a capacitor across a battery with
voltage "V" will eventually charge the capacitor to "V"; putting a
resistor in series with the capacitor won't affect the final potential
across the capacitor: it will still eventually reach V. However, it
may take longer... perhaps a _lot_ longer. grin!

Makes sense: If I have a "vacuum-formed plastic object" production
line, I probably care whether it takes minutes, hours, or days for the
vacuum at the mold to reach the right level. Or am I missing
something?

Thanks.


Frank McKenney
--
Nearly every feature of the American system of manufacturing, from
the elements of the new textile machinery to the concept of
interchangeable parts, had actually been conceived earlier by
Europeans. But while a few Europeans could see the possibilities,
their communities kept them powerless to give their ideas a free
trial. Too many had a stake in the older ways. Industrial progress
in Europe required extraordinary courage to break the prevailing
pattern; in America it required a willingness to try the obvious.
American genius was less for invention or discovery than for
experiment.
-- Daniel J. Boorstin / The Americans: The National Experience
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney aatt mindspring ddoott com