@rivstg1
"tests on airflow, and contrary to your comment that the direct air machines weren't as good as tandem machines, I couldn't find any tests showing that....only found the opposite. I did find the 'working water lift' test heavily favoring those machines though. " I couldn't find this comment on vacuum land and unfortunately I've shot too many videos at this point to recall saying that. If you could put it in some context for me that would be great.
I don't think there's really any doubt that tandem Air machines carpet clean better then direct air only machines.
I did go back and read watch the video I made on the Kirby to make sure the height adjustment was adjusted. At 26:00 minutes in you can clearly see the height adjustment and it's later shown in a point of view camera as well. The machine was properly adjusted for my high pile carpeting.
Now if you're implying that one would change the height adjustment just to pick up some extra debris. In that case I think you're proving my point further and putting another nail in the coffin of the generation series.
A little bit later in the video 27:30 I do go on to explain why the results were that way.
as far as the water lift rating being important to me ,the more water lift a vacuum cleaner has the best it is at picking up heavier objects.
So in an ideal World I'd like to see a vacuum cleaner have 100" of lift and 150CFM
I don't believe we'll ever see these numbers from a portable vacuum. But they're pretty realistic numbers for a central vacuum.
The working vacuum gauge gives you a nice way of testing things in their practical cleaning ability.
I hope that clarifies everything.