dusty wrote
I have a 36" hood and it fully inflates (for whatever that is worth).
What would I gain by changing to a 42" hood other than the claim that it captures smaller particles.?
What is lost by having a taller hood that does not fully inflate.
Does the cake that develops in the hood help or hinder and how? When I change collection bags, I've been knocking all that cake off.
I don't see a reference to a 36" hood, so that may be an older version(?) SS currently offers 12", 24", and 42". For each increase in hood size, they show a decrease in particle size and an increase in CFM: "Advantage of the 24" filter hood on DC3300 is that it increases airflow 30% or from 330 to 430 CFMs. 42" hood CFM range 695-890 hose is 2 1/2". Diameter plastic end makes it 2 1/4"." From:
https://www.shopsmith.com/mediawiki/index.php/Micron_Filtration How these numbers were derived and/or tested isn't included. If the numbers were accurate, which I'm not claiming, a DC-3300 with 42" hood has more CFM than a DC-6000 with standard hood. The hoods fit both versions.
Nothing is lost by the hood not fully inflating. Not fully inflating suggest there is very little pressure drop across the filter and that it is not limiting air flow much, if any. So in this case the filter is no longer a 'bottleneck' and could presumably handle considerably more CFM. But if the DC-6000 fully inflated the same hood that would mean more pressure drop across the same filter, which can only be caused by more airflow. Basically it's a poor man's verification method of increased air flow. Especially true if full inflation occurs with only two inlets open, because that would mean more CFM even with more inlet restriction. I'd think it would be hard to observe the difference, and there might be less of a difference, with the smaller hoods.
- David
