Thien Cyclone done! Pics coming...

[cgallery]

why the focus on measuring absolute flow? relative numbers, such as measuring restriction, would give you an indication of efficiency.

I already have what I consider very good relative #'s.

So any focus now would be on even more accurate #'s, or repeatability (where other users could duplicate my tests and get similar results).

[AlanWS]

I've not tried it, but one simple approach that could in principle give you not only the flow rate, but its distribution across the duct, is as follows. Attach a transparent tube the same size as your other duct to your DC. Set up a camera with either a timed flash, or brightly lit with an accurately timed shutter. Take a few pictures as you let it suck up some light colored particles, against a dark background. The length of the streaks on the image will show the speed of the particles, and those toward the edge of the duct should be shorter (slower) than those in the middle.

[cgallery]

Wow Alan, that is an interesting idea. I wouldn't want to resort to film, and my current digital camera isn't sophisticated enough to let me set a shutter speed.

Maybe time for a different digital camera...

[chopnhack]

are you thinking about having a black background with regularly marked white lines? and by knowing the timer speed and the distance between lines you can extrapolate speed? an interesting thought Al

I've not tried it, but one simple approach that could in principle give you not only the flow rate, but its distribution across the duct, is as follows. Attach a transparent tube the same size as your other duct to your DC. Set up a camera with either a timed flash, or brightly lit with an accurately timed shutter. Take a few pictures as you let it suck up some light colored particles, against a dark background. The length of the streaks on the image will show the speed of the particles, and those toward the edge of the duct should be shorter (slower) than those in the middle.