Shopsmith Forums

oscarthefuzz wrote:...can anyone explain the science behind why one inlet being left open would increase the air flow?? I don't get it...

I don't get it either, Oscar!!! Also, I disagree with this thinking. Reading the advertisement by Shopsmith for the 3300, they point out the air speed differences when using different number of hoses.

Found this old thread which seems to go into it in some detail https://forum.shopsmith.com/viewtopic.php?t=7290

Have only started reading it now but will hopefully have a better understanding when I get through it...

oscarthefuzz wrote:Found this old thread which seems to go into it in some detail https://forum.shopsmith.com/viewtopic.php?t=7290

Have only started reading it now but will hopefully have a better understanding when I get through it...

I am anxiously awaiting your input. I am just as confused as ever; even after reading these threads still again.

Something does not add up. I believe Shopsmith has said the DC3300 moves 330 CFM. But according to PTWFE (also by Shopsmith) there is no way to move 330 CFM with any number of hoses attached. I base this on the chart in PTWFE which provides that the airflow with 1 to 3 hoses (2.5 x 8) is as follows:

No. of Hoses...........CFM

1..........................107

2..........................100 Each

3.......................... 95 Each

It is thus clear that airflow per inlet decreases as additional inlets are opened. Thus, PTWFE states: "[P]lace an inlet plug assembly in any inlet not being used. These plugs help to muffle noise and slightly increase the suction power. If you desire, you can leave inlets open to help filter dust from the air."

In sum, Shopsmith says you will get the best air flow through a single hose by closing off the other inlets.

Perhaps you get 330 CFM if you open all three inlets up without connecting any hoses (110 CFM per inlet?) in an effort to make the DC3300 into an ambient air cleaner versus a dust collector.

This 'plug' does not also provide the hose reduction feature of the SS version, but it is a 'GREEN' alternative with negligible cost(available due to other needs!).
[ATTACH]18076[/ATTACH]

According to the chart, the sum of the three ports is only 302CFM. We have lost 28CFM somewhere.

I am just confused.

dusty wrote:According to the chart, the sum of the three ports is only 302CFM. We have lost 28CFM somewhere.

I am just confused.

Not 'specified' in those charts is the loss due to each hose.

I believe the '330' is with no hoses attached. As hoses are attached or ports plugged, the total flow rate is reduced.

Do not be confused.]all this is not a+b+c[/B]. All three interact with each other and the dc3300. Also that chart assumed an 8' hose attached to each port.

How about another confusion factor? Air flow (CFM) and suction are not the same. :D

curiousgeorge wrote:How about another confusion factor? Air flow (CFM) and suction are not the same. :D

Air flow is amount of air per time (volume per time).[Cubic foot/minute]

Suction is static pressure (force per area).[pounds/square in]

No confusion, they are simply two different things!;)

I do not claim to be a scientist or intelligent. However after reading the original discussion on this subject tried different numbers of hoses and purchased the gates that allow partial opening of any or all or none of the gates.

What I found first hand is;

1. With one gate open at least half way with NO hose attached and only one hose attached to a separate totally open gate I pick up a greater amount of sawdust thru the open hose and the airborne dust is diminished almost totally.
2. Today I have been turning a Black Walnut bowl. My lathe (not a Shopsmith tool) sits further away from the dust collector than any other tool in the shop. As such requires a second length of hose. This creates a less than ideal dust collection percentage. However it picks up a fair amount and keeps the air quite clean.
3. I tend to generally operate with one hose connected to the Power Pro another hose attached what ever other tool I may be moving between and both of those hoses attached to the DC3300. I will also open the third port fully and find that most dust is collected from machines in use and drawn from the air. Now here is the part of this that has always fascinated me. The open port (with no hose on it) is the port facing down toward the floor and still never allows any of dust collected to escape and fall to the floor.

You fine folks may argue this stuff till the cows come home to roost. I would rather turn my bowl. Jim