Hi So if dyson did reposition the cyclones put the top at the bottom and bottom at the top,in reality what difference did it make.Was this just a make work project for the engineers?
 
  O.T.

Quote from Carmine_Difazio on 04/18/07 at 6:28pm:

Apparently Dyson inverted the cyclones in the DC14 and later because in their testing the new designs work better and/or are less prone to clogging. Why would inverted cyclones work better? To me it seems logical that the cyclones would be less prone to clogging with the big side down because dirt would easily fall out, and because it would be difficult for dirt to cling to the side walls. It seems to me, just as it does to you, that an inverted cyclone would be more prone to clogging. Certainly it would be more complex to build and more difficult to clean.  
 
As for why the inverted cyclones may work better, I'm just speculating here, but perhaps an inverted cyclone (with a hole at the bottom) would function very much like the primary cyclone, with the air going down around the outside, and coming up the center. The dirt would then settle to the bottom, and fall through a narrow opening into a collection chamber. In the more logical DC07 design, with the wider side down, as I think about it, the problem would seem to be that the falling dirt would tend to intersect the airpath, and could end up escaping the cyclone. Perhaps the heaviest of the dirt still light enough to get to the secondary cyclone (i.e. sand) would be heavy enough to fall into the airpath and escape, while the lighter dirt would have less tendency to do so. That would explain the odd tendency of the DC07 to allow some sand to get to the premotor filter while at the same time catching almost all drywall dust, a trait that I have always thought was bizarre.  
 
As I think about it, I guess, it doesn't surprise me that the inverted cyclones on the DC14 have less dirt escape and get to the pre-motor filter. As I understand it, the pre-motor now only needs to be cleaned annually instead of every 6 months (3 months in my use). As for their tendency to clog, I guess the real test will be real world use.

Hello Carl:
 
Correct me if I'm wrong, which I have tendency to be now since I retired, but didn't you say that a clogged air filter works better than a new one because it keeps out more of the dirt/dust.  I think you were making an anology of a vacuum filter to a water filter, If I recall the post correctly?
Am I wrong?
 
Carmine D.

Quote from Carmine_Difazio on 04/18/07 at 7:43pm:

Using a standard vacuum bag as an example, when new, a lot of fine dust passes through the bag. As more and more dust begins to pack the inside of the back, the dirt improves the filtration, and less and less dirt gets through the bag. Thus while all pollens would go right through a brand new bag, some would get caught in a full bag because it would stick to the other dirt. That's the positive side. The negative side is that less and less airflow also gets through, so the airspeed begins to drop. For the Dyson, where airspeed it critical to proper functioning of the cyclones, the loss of airspeed would be a much more significant loss than any possible gain from improved filtration.
 
As regards the advantages of an inverted cyclone, I'll defer to Jim. My theory is just speculation, and he may well have seen some actual literature from Dyson explaining the switch.

Quote from JimB on 04/18/07 at 7:41pm:

Yes, I see that now. In my text picture above of an inverted (DC07-style cyclone), gravity would tend to pull the dirt particle back down, into the airstream, whereas in an inverted design gravity would would in the same direction as the centrifugal force, tending to keep the dirt particle against the sidewalls, and separated from the airstream.