I aquired some metal dust gates and had to figure the best way to use them. The final ddd Ed vision was to remove some of the box collection points and straighten the lines. Well forgot to take a pic of the first area completed.

 

 

 

 

 

 

 

This is the before. Ok maybe there were some modifications not in the picture.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This is what things looked like when I started today. Started on this before the covid and worked a little yesterday.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This is the duct collection I hope the straight in run will enhance the suction on, by eliminating the air bouncing around in that collection box and also end the leaks from homemade gates.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

here is a closer look at couple gates I installed yesterday.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What is now a collection box for large chips that the ducts empty into. This is from a Shop Notes plan , issue 55.

 

 

 

 

 

 

 

 

 

 

 

 

 

Two ports ready for ducts and one more to do. That one protruding at the back goes to the Dust Deputy.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now ready for install of the ducts tomorrow. That other port on right rear goes to the Oscillating Spindle sander.

 

 

Edited January 18, 20224 yr by Gerald

You must be feeling a little better? You've been busy. Are your main runs 4"? Just nosey

A lot of work @Gerald but should be worth it with improved efficiency. 

A couple of things that might help from standard duct design:

--Two 45's are exactly the same as one 90.  

--Try to find "long radius" elbows; they can cut pressure loss in half

--Use a reducer (e.g., 4x5 or 4x6) at a box connection; the longer the transition = less pressure loss (consider using sheet metal fittings which have more options)

--If you can't use a reducer at the box, stub the duct 2~3" into the box; that reduces pressure loss at the wall of the box (yeah, non-intuitive)

--Fear not the use of duct (or duck) tape:  on negative pressure apps, it seals rather well, and most DIYers keep fiddling with the configurations so that the tape comes off for changes long before it becomes useless

12 hours ago, Grandpadave52 said:

You must be feeling a little better? You've been busy. Are your main runs 4"? Just nosey

Yes mostly 4 but couple years ago when installed the dust deputy there is now a 5 inch from it to the DC. 
 

Pete I have changed this collector configuration about 6 to 8 times in the last 25 plus years and that insert the pipe idea is a new one to me. Thanks. 

1 hour ago, Gerald said:

that insert the pipe idea is a new one to me. 

High velocity air at a flat bulkhead will lose all of its velocity pressure, sometimes a bit more as the air "shocks" into the cavity [speculation:  the incoming air forms a vacuum against the bulkhead, which pulls the air back with a lot of turbulation].  The inserted short duct allows air to draw in behind the discharge nozzle, breaking the vacuum.  If you have a 4" suction pressure, and 4000 fpm velocity, the insert duct can improve air flow by about 15~25%.

 

32 minutes ago, PeteM said:

High velocity air at a flat bulkhead will lose all of its velocity pressure, sometimes a bit more as the air "shocks" into the cavity [speculation:  the incoming air forms a vacuum against the bulkhead, which pulls the air back with a lot of turbulation].  The inserted short duct allows air to draw in behind the discharge nozzle, breaking the vacuum.  If you have a 4" suction pressure, and 4000 fpm velocity, the insert duct can improve air flow by about 15~25%.

 

So if I understand right the incoming duct should protrude into the box but that is not necessary for the outflow to the DC.?

The outtake pressure loss (to the DC) from the box isn't improved by a stub of duct into the box (difference between directions of the air).  However, if you can use a sloped transition "scoop" (ex:  for a 5" hole to the DC, use a 6x5 transition), you get a boost of about 10% in performance.  Air doesn't like sharp edges.  

Got it done yesterday and after all that work could not tell a difference. Went to attic, opened the filter and found it to be clogged with lots of dust. Cleaned that out somewhat and doing well now.

Most gates now relocated to this stack area. This is in center of shop and allows changes at one place for the most part and the addition of metal gates should eliminate some leaks.

I could not totally eliminate the flex but managed to reduce the amount somewhat. Have one more connection to the joiner but have to cut the flex to length. This may be worse in the doing than the first install but hopefully this will do it.

 

Improvements are hard to "feel" without test equipment.  What happens is you make a duct change that reduces pressure loss by 20%.  But pressure increases by the square of air flow, so the net result is only about 10% increase in air flow.  Absent test equipment, you'd never detect 10%.  Straight runs, whether smooth or flex surfaces, don't use much pressure (flex is about 400% the loss of smooth), but fittings (elbows etc) get all the action and flex bends can kill ya.  

I just got dust collection envy. Glad you’re feeling better Gerald.