I have to wonder as the diameter of duct increases ,using the incompressable
fluid formula [and I am well aware air is compressable] ...Q=AV where A is
the duct area, V is the velocity in the duct and Q is the volumetric flow
rate , then the velocity will decrease for a given flow rate .

Considering the above seems to me the heavier dust particleswill just fall
to the bottom of the duct and stay there as the velocity gradient there is
theoretically zero, that is until enough of them are deposited to reduce the
effective area and in turn increase the duct velocity. To me it's kind of
like which came first the chicken or the egg, I suppose at some point the
whole thing stabilizes ???mjh







"Mike Hide" wrote in message
news:igk4c.16819$mM.121801@attbi_s02...
I am talking about the oversized duct diameters .....mjh

"Jay Chan" wrote in message
om...
I have to wonder as the diameter of duct increases ,using the
incompressable
fluid formula [and I am well aware air is compressable] ...Q=AV where
A
is
the duct area, V is the velocity in the duct and Q is the volumetric
flow
rate , then the velocity will decrease for a given flow rate.

Honestly, I don't quite understand what you said. But I have a feeling
that you are referring to the 45-degree lateral-tee that I want to
connect to the 6" inlet of the dust collector.

The 45-degree lateral-tee that I mentioned in my original message has
a 6" outlet and a 6" inlet with a 2" side inlet. This means the
combined size of those two inlets will be greater than the outlet
size, and I intend to use both inlets at the same time to capture dust
from my table saw. This means the inlet size will be greater than the
outlet size. This means I may have a the bottle-neck at the 6" inlet
of the dust collector. This is probably what you are referring to. And
I probably need to reduce the combined size of the inlets of the
45-degree lateral-tee to match its outlet size. This sounds like a
reasonable concern to me. Thanks for warning.

This means I will need to use a different 45-degree lateral-tee. I am
thinking of getting one that has a 6" outlet and a 5" inlet and a 2"
side-inlet. If such a fitting is not available, I probably need to get
one with a 3" side-inlet and then use a reducer to transition it from
3" to 2". According to books on dust collection, a 5" duct to a table
saw should be good enough. Good, afterall hoses/fittings for 5" duct
are cheaper than those for 6" anyway.

Thanks again.

Jay Chan