Sebo D4 airflow losses

[blackheart]

So after trying to do this i've discovered my readings to be incredibly inconsistent and frustrating as such this may be the first and last airflow loss post i make. It seems that when i try to measure a machine there are just too many variables (hose curvature for example) and perhaps even my anemometer. The numbers have shifted a little bit since my initial purchase as there is a little dirt in the bag as when it was brand new it was pulling 102.75 from the hose. It could just be a fluke in measurement or perhaps the dirt has effected it a little.

I'm also unsure if Bill counted the area the belt occupies as part of the opening, i did not. So the density may be a bit lower if that's counted. Either way despite the high loss at the nozzle it still has a pretty wonderful airflow density.

 

[wyaple]

Excellent work Devin!

Finally! I have inspired someone else to create an airflow box and post measurements. It's great not to be alone in this endeavor anymore. Please keep going and I'll help you as much as possible.

As far as testing goes, here are my suggestions:
1) always use fresh bags/filters to get the max performance if possible.
2) When measuring, I stretch any hoses out completely straight and level as that's what I've seen other manufacturers do when they test.
3) If a power nozzle is involved, recline the wand to a 45 degree angle. This means you'll have to raise the entire (primarily canisters) vacuum several feet off the floor in order to have the nozzle be at floor height.
4) Since you're using a GM8901 anemometer, it only generates 4 significant digits, so only report results to a maximum of 4 significant digits. Use proper truncation and rounding rules when required. I usually report most of my specs only to three digits because few would care about more than 0.1% accuracy anyway.
5) I usually include "belt guard" area if the guard path actually can still effectively pick up dirt. In the case of Kirby, the belt guard area can (line of shame is mostly minimal).

Great job!

Bill

 

[wyaple]

Now onto a critique of the D4's performance

So from the hose end (I'm going to round here) to the PN base, I see a loss of 102-94=8 CFM. That is excellent. BUT, the total PN loss of 94-71=23 CFM really hurts the performance. Is anyone surprised or disappointed that such an expensive machine only does 71 CFM at the nozzle? My 1980 Lux 1401-B (with a new vinyl hose) does 75 CFM at the nozzle.

The D4's nozzle area appears to be extraordinarily small. At 11" x 1.5", the area would only be 16.5 square inches. That's barely larger than an Oreck XL2800 and slightly smaller than a Dyson DC25.

Excited to hear everyone else's thoughts...

Bill

 

[blackheart]

Good to know

With the belt guard area included we'd have a surface area of 18 in² making cfm density of 3.96 cfm/in²