Shopsmith Forums

RFGuy wrote: Sat Jul 03, 2021 2:50 pm The instrument used to measure it is called an anemometer, but you have to get one with a high enough range to measure very fast airspeeds such as a dust collector can provide. Mine cost about $130 and has come in handy for HVAC adjustments as well as evaluating dust collector performance in the shop, but not a tool most woodworkers need or will want to purchase.

DLB wrote: Sat Jul 03, 2021 4:52 pm What velocity range does your anemometer have? What range do you think is required? I know there are some much less expensive, as well as much more expensive, anemometers out there.

- David

DLB wrote: Sat Jul 03, 2021 6:25 pm Getting back to Dusty's original question about subjective measurement, the 42" hood on the DC-3300 provides a built-in subjective indication of airflow based on how firmly the filter hood inflates. Mine does not fully/tightly inflate in any natural configuration of the DC. But how fully inflated it is is a subjective indicator. For example at the two extremes: with no hoses attached and all three ports open it is almost fully inflated. With one hose attached to some tool (I used a jointer) and the other two ports blocked it is not at all firmly inflated. Every change in between those that I make that allows more flow can be observed on the filter hood.

I don't know how well, if at all, this translates to the other filter hoods. One could try adding a weight in the middle of the hood to deflate it a bit. (This worked on the 42" but was not as clear as the hood by itself.)

In looking at this, my observations conflict a bit with the CFM statements that Jim made. Possibly because of the allegedly higher CFM resulting from the 42" hood? In any case, I can observe significantly higher airflow on my DC if I start from two hoses connected (but not connected to a tool) and then remove the plug from the third port. Significantly higher, based on firmness of inflation of the hood. Jim's data would lead me to expect no change, at least if I was using the OE hood, because max airflow (300 CFM) is already present through two hoses.

- David

algale wrote: Sun Jul 04, 2021 1:12 pm The collection bag inflates too. So air is filling that 30 gallon plastic bag as well as the hood and escaping the hood.

reible wrote: Sun Jul 04, 2021 6:15 pm I would think the more dust collected on inside of the bag the less air will pass through so less escaping air the fuller the bag will feel. So a bag with a lower size pass through will also lessen air flow. At some point the bag will be the controlling factor as it is just like a clogged filter. I can't say when that happens........ I would worry about the feel of the bag as a test method.

I have this:

https://www.amazon.com/gp/product/B00ZH ... UTF8&psc=1

While not designed for dust collector system it sill works for air flow and should show the difference between systems. You may not get accurate results in terms of absolutes but for relative measurements it should work. For the less then $30 range of solutions this is a decent one.

Ed