Hey Mikey.
I've been watching this thread and deliberately staying out of it as I had no knowledge of a machine that met all the criteria you specified.
But, subjectively the thread seems to be going nowhere fast and so I wondered if you might be receptive to some observations?
Our business has two complimentary divisions. Carpet cleaning services and vacuum cleaner repairs, parts and service.
We see a few machines and get to try a lot of varied types out. Based on this I have come to think the following.
Real vacuum cleaners have a fan that is as close as possible to the carpet. No cheating, no putting the fan behind the dirt collector or bag. For maximum carpet pickup performance the dirt must go through the fan on the way to the bag. In other words, unless the machine is a dirty fan "direct air system" design, you've already lost because the frictional losses and pressure drop of clean air "indirect air systems" is too large to be effective.
You want the fan openning to be as wide as possible and in the centre of the cleaning head. There is no point in biasing the air delivery to only a portion of the cleaning head; and there is no point in having the openning to the brush roll channel insufficiently sized to effect debris removal from the head.
Bagless designs inhibit airflow. When air is forced to change direction many times, travel further than it should, or flow turbulently it's wasting efficiency and accordingly performance. The air path should be as short and as wide as possible. Think about how traffic flows on a freeway, a short route that's nice and direct and has plenty of lanes is WAY better than a longer, narrower long winding route with insufficient lanes.
As the ladies say..... Size matters. Where filters are concerned this is absolutely true. Rip a bagless vacuum cleaner apart and get a ruler and measure the filter surface area. Now measure the filter area of a typical dirty fan machine's disposable bag. HUGE difference right? Any air that enters the machine had to escape, if it can't than the air behind it can't move on, and neither can the air behind that. Furthermore, many bagless vacuum cleaner manufacturers make outrageously fallacious claims about not losing performance. Yet these same manufacturers go to great lengths to ensure users clean their filters. If cyclonic separation were the best thing ever, then there would be no need for filters, and yet bagless machines have filters and they get soiled, why?
What happens when our bagless machine with its' paltry filter area begins to dirty the filter?
Correct height adjustment matters. We need the machine to get close enough to the carpet that it can make contact, but not so close that it will wear the carpet, pull yarns or restrict airflow that will impede soil recovery. So adjusting the height from the rear isn't ideal because it will simply - push - the vacuum head into the carpet effectively cholking it. So what is needed is for the height adjustment to allow the head to descend only as far as needed to permit the airflow to - lift - the carpet and allow air to be dragged all the way through the bottom and middle of the carpet and out the top. This way we get - deep- dry soil extraction.
So the height adjustment should be progressive and implemented on the front axle - not the rear.
So we now know we need;
Dirty fan setup
Centrally located air intake port
Short - wide air path
Large filter area - ideally disposable
Height adjustment on front axle
Sound like a particular - well known American made upright?
Grant
LOL
