Woody's formula happens to work only for 4" hose because the radius squared
happens to be the same as the diameter at 4". Otherwise you are not
calculating area of the hose at all, rather it's circumference (see below).
Beyond that, there is a trade off between air speed measured in Feet per
minute (increased by smaller hose, to a point) and volume measured on Cubic
Feet per minute (increased by large hose and less restrictions). Limit
either one too far and the whole setup won't work as well.
3.1416 x diameter is circumference. Area is 3.1416 x radius (squared).
4" = Circ 12.5664 area 12.5664
3" = Circ 9.4248 area 7.0686
2.5" = Circ 7.854 area 4.90625
Excellent info found at
http://cnets.net/~eclectic/woodworki...20Introduction
That said, this was not intended to be a shot at Woody, or anyone else.
Bob by Chicago
"Joe "Woody" Woodpecker" wrote in message
...
My reason to say think is --- When purchasing a DC, it is designed as
the standard 4" type system because the market shows tools with 4"
ports. And then a dummy doesn't have to read "Connecting Woodworking
Tools To A Dust Collector For Dummys"
My system starts out as a 4" system to the separator can. It leaves the
separator can in a 3" line to a short manifold. There it branches to
2-1/2" lines where shop vac hoses connect the manifold to the tools with
a 2-1/2" blast gate at the tools. Each of the after thought dust ports
are redesigned to work on a 2-1/2" line. I have excellent pickup from
everything from the router to the planer and even the TS after a well
made dust collection port has been made.
So, think. If a shop vac will pick up the dust after it is made just as
fast as it is made, then a shop vac or a DC with a shop vac hose will do
the same.
When you go from a small lineal area to a larger one such as that is
what happens in your separator can or cyclone, then the suction is
decreased and the dust won't flow. The only thing size of the DC will
do is overcome this change and make no need to read the above book for
dummys.
However, when the dust port is redesigned so that the lineal area of the
hose (ie. 3.1416 x 4 = 12.5664 for 4" hose; 3.1416 x 3 = 9.4248 for 3"
hose; 3.1416 x 2-1/2 = 7.354 for 2-1/2" hose) is nearly the same as the
port. This makes the port move suction like the hose and the chips and
dust move in the hose and tool as they were one regardless.
However, it is easier to just buy a bigger DC to compensate for the
change made from the hose to the port because most WW'ers don't have the
ability to redesign the dust port, so they just hook up a powerful DC to
after thought dust ports.
BTW, where were these dust ports on tools 30 or more years old, & why
hasn't there been significant change in the DC collection on a TS where
DC collection is needed most?
--
wrote in message
SNIP
The larger machines that have the 4" collection ports are placed there
as an after market product to match up with the existing standard of the
4" dust collection hose. Think!
SNIP
--
What are you trying to accomplish by telling the poster to "Think!"? At
best it seems condescending, bordering on rude. I believe that you could
have effectively made you point, and spread some good will at the same
time without the attitude.
Bob McBreen - Yarrow Point Washington
--
Woody
Check out my Web Page at:
http://community-1.webtv.net/Woodwor...workerJoesInfo
Where you will find:
******** How My Shop Works ******** 5-21-03
* * * Build a $20 DC Separator Can Lid. 1-14-03
* * * DC Relay Box Building Plans. 1-14-03
* * * The Bad Air Your Breath Everyday.1-14-03
* * * What is a Real Woodworker? 2-8-03
* * * Murphy's Woodworking Definitions. 2-8-03
* * * Murphy's Woodworking Laws. 4-6-03
* * * What is the true meaning of life? 1-14-03
* * * Woodworker Shop Signs. 2-8-03