On Tue, 2 Apr 2013 06:18:13 -0700 (PDT), wrote:

On Tuesday, April 2, 2013 7:56:24 AM UTC-4, Frnak McKenney wrote:
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

It all depends on what you are doing- vacuuming stuff up requires a lot of air flowing quickly, you would need significantly less volume flow to quickly evacuate a mold. But, a long hose would give a lot more space you'd have to pull air out of, so the most significant effect wouldn't be from the drag of the hose, but the volume in it.
Which is not an issue if the vac is applied to the hose ahead of
time,with a "gate valve" at the vac former - which is "standard
practice" in production vac forming.