Thread: Duct work lengths

Mini – yep the whole purpose of a new second mini-shed is to get the extracted dust out of shed No 1 and avoid the “blow-out” fine dust. This’ll finally flip my home-brew wiring – so will call in a sparky to add full board and extra wiring into shed’s and switch for dusty in main shed.
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BobL – great tips (greenie) will certainly do this – ta.

Originally Posted by Mini

I alluded to to this effect in another thread. I will try and describe what I think is happening. If there is a source of air upstream from a branch the air from upstream is passing the branch and causing a depression. If the upstream supply was too large this depression would not exist as the system would not need any more air in the main branch. So careful sizing of an upstream supply might make downstream branches more efficient. I might have it all wrong of course and will await more qualified comment.

Your description is basically correct, it's a venturi effect where the added airflow in the unconstricted pipe produces a further pressure drop in the downstream constricted pipe, which in turn increases the flow rate. (BTW, it doesn't seem to be the case for my 1HP 30 micron bag setup.) In the case of your's and mini's set ups you would further improve the air flow from your constricted intake by putting an open port as close a possible to the constricted intake. This will also sweep the dust away more efficiently.

In my diagram, if machine B has the constricted intake, adding an open y-connector at C will produce the greatest pressure differential and improve the air flow from B.

Originally Posted by Waldo

. . . .as I'd think running from shed to shed to turn the Dusty on and off would be a pain in the neck.

I did this for about a day before realizing it's actually very simple to move a dusty's magnetic switch to where you need it. The standard switches use 4-core wire which is a pain to find although you can use two lengths of 2 core. My dusty is immediately outside the shed so I only needed 1m of cable and I used a bit of left over 7 core trailer wire.