Airflow vs. Suction

[methodistbill]

Can someone explain to this vacuum cleaner novice why good suction AND airflow are both necessary. I had an Electrolux Epic 6500 that had strong suction but its airflow didn't seem great. It never groomed the carpet as well as my other Electrolux vacuums do. I put a new brush roll on and had no improvement. The ancient PN1 on my Model L did a better job. But the Model L always seems to have better air flow too. I've been wondering if the poor airflow on the Epic 6500 was the culprit or the design of the plastic wand power nozzle. I remember reading somewhere that good airflow is necessary for raising the nap on a carpet. So I guess it's not all up to the brush roll. Also, how can a vacuum motor produce strong suction and poor airflow? Thanks!

Bill

 

[electroluxxxx]

Hey Bill!!!!
I too am wondering the same thing.

 

[tommymilan]

Hi, I've always had the feeling that airflow is very important when it comes to carpet cleaning but, in my experience, the airflow produced by traditional upright cleaners (hoover convertibles, kirbies etc.), in general bypass motor with direct air systems, especially with fan very close to brushroll, is much more effective that higher suction produced by separate motors, with some exceptions of course. other opinions?
tommy

 

[rolls_rapide]

I agree

The air displaced by the old "dirty fan" Hoovers exceeds that of the modern machines. And the old cleaners give the carpet a decent beating; those new-fangled things either barely tickle the surface, or else they brush the carpet to death, using stiff bristles.

I still believe in the tried and tested HOOVER method of agitation!

 

[rolls_rapide]

Suction / airflow

It is all to do with design. If a fan is almost open to the air (as in the traditional Hoover or Kirby), it can shift large amounts of air; thus it has good airflow, but poor suction capability.

If a fan is placed in an enclosed chamber, it creates a vacuum in said chamber. Air rushes in to fill the space, as nature abhors a vacuum. If you employ narrow hoses, the suction power is then focussed to the hose end.

I once saw a brochure for the UK Hoover 'Alpina' cylinder cleaner. It had a mickey mouse graph purporting to show the relationship (suction power), between vacuum and airflow. High vacuum means little airflow; high airflow = low vacuum. The sweet point is somewhere between the two extremes; if I remember rightly, the graph was curved like a pincushion.

Remember also some cleaners have good seals at joints, casing, nozzles, etc.; some other machines leak air something chronic at hose and tube joints.

 

[dirtfinder1]

Electrolux Epic 6500

The 6500 powernozzle or the "N" series as they are refered too have small openings along the front and sides of the base to allow airflow in from all directions except from the back. The main issue with that stlye nozzle is not airflow but actually the rear wheels. They are spring loaded and sometimes the spring was defective or not in the proper position so the wheels did not keep the front of the nozzle flush against the carpet. And because of the base design if there is any tilt towards the rear of the nozzle the brushroll would not make good contact with the carpet. The older powernozzles had a retainer wire which would hold the axles down but that was absent on the "N" style powernozzle.

 

[tolivac]

As I have seen "Airflow" and Suction in some vacuum sales manuals-Kirby-"you got to move the air to move the dirt"-filter queen-"suction dislodges the dirt-airflow carries it away"FQ's saying makes sense-they both do.Yes you can have "suction" but if there is no airflow or movement-you don't accomplish anything.The air has to flow to get the dirt from whatever you are vacuuming to the bag or container.If the bag or container-or hose is clogged your airflow is cut off-the air isn't moving or flowing.So no dirt movement.the air movement carries the dirt.Its like with water or electricity-if they don't "move" or flow no work is accomplished.Yes-traditional fan first designs do emphasise airflow rather then suction.Axial motors used in clean air vacuums-with two or more fans develop MORE pressure-or suction-but less flow.In both types of systems the fan(s) are in a fancase to concentrate the suction and flow.A fan spinning in free air doesn't do much.You need the case or "scroll" to direct the air flow.In the deal with the "axial" motors the fans are in series-one blows in into the intake of the second-like the pipe organ compressor blower in one of the other threads.This would be like a giant clean air vacuum cleaner fan system.Tradional dirty air vacuums have only one fan-so less "suction" but high airflow because of the size of the fan and air intake-discharge openings on the fan case.and of course the tradional air fan system is closer to the surface being vacuumed than a clean air vacuum system.

 

[swingette]

Suction/waterlift: think force or strength. An air compressor, the kind used to power a ratchet, creates very strong air pressure but doesnt move a lot of volume. A clean air machine needs strong suction to keep the narrow dirt path from clogging and to overcome the resistance from the usually smaller bag. Provides lots of strength when air is forced thru narrow openings, like a crevice tool.

Airflow: volume of air. Think a large table fan. A large table fan can provide enough airflow to cool an entire room of people, but would never have the strength to blow up a tire, like a compressor would.

The best carpet cleaning happens when the agitator can vibrate the carpet, and when the nozzle is designed to allow air to flow thru the carpet fibers. Clean air machines often have vents in the nozzle to allow airflow ABOVE surface of the carpet. This is to prevent the machines strong suction from grasping the carpet too firmly and making the machine too hard to push. Unfortunately, too much venting on a nozzle shoe sacrifices deep cleaning ability. Think Dyson.

Traditional fan-first designs move large quantities of air thru larger corridors. Not strong enough to lift a bowling ball, but voluminous enough to be effective through large nozzle openings and on sculpted, textured carpets than can diffuse the suction. Ever notice how a traditional machine like Hoover Convertible has enough airflow to draw in stuff like leaves or candy wrappers, sometimes inches away from the nozzle openings?

The ability of a traditional machine to raise its nozzle slightly above the surface of the carpet can allow for more rug vibration at the nozzle opening. This also prevents the weight of the nozzle itself from squashing the nap.

 

[swingette]

PS

Good morning, Rex!

 

[tolivac]

Good morning Brett! welcome to the mid shift!As I type-I can hear the sound of the switchbay aircompressor running.Need to hear that sound or I can't switch antennas onto my transmitters.
On any older kirby website-they claimed their G6 vacuum in hose mode could lift a VW car full of ball bearings-would love to see the "attachment" they used-was to counter the claim of lifting bowling balls-I think any vacuum in its hose mode could lift the bowling ball with that large funnel shaped attachment.Yes-i have noticed on direct air vacuums-not just the Hoover convertibles- on Kirbys,royals,Eurekas that they snatch up light peices of floor litter that are close to the nozzle-that also shows proper nozzle height-you have "airflow" working for you!!In my case after I eat my breakfast-the Cheerios I spill get picked up in that way.

 

[compactelectra]

Here is a link to a discussion

Of the relationship between airflow (CFM) and water lift (suction) in vacuum cleaners. They both are important and related.


http://builtinvacuum.com/education/definitions_b.html

 

[kirbysthebest]

I have always been told that suction is great, but it's the air flow that cleans. Take the Oreck commercial for instance. That little hand vac can "lift" a bowling ball, but it isn't moving any air. If there was a speck of dust on that bowling ball it would stiil be there when the machine was shut off.

Now put a feather, a piece of paper, or something else of that nature outside on a windy Kansas day and it will be in Nebraska by night fall. The air flow carried it away.

Kirby is a good example of a machine that has air flow, but not as much suction or water lift. It's fan first design is efficient becuse the fan is spinning so close to the area it is cleaning, hence it can form a good suction briefly. I wrote this once before, but couldn't find my posting right off.

Kirby has tremendous air flow, by moving the large amounts of air through the bell shaped nozzle it forms the suction close to the carpet area. This is in effect the Bernouli principal. The air rushes in to fill the void in the larger portion of the nozzle close to the carpet carrying dirt and other goodies with it. It is carried upwards towards the fan housing where the opening narrows and volocity increases, it then goes through the fan to the bag assembly where the large surface area then drops the air pressure back to ambient and the vacuum cycle is complete. This allows Kirby's "Tripple Cushion vibration System" when properly adjusted, to slightly lift the carpet the vibration loosens the dirt and the airflow carries it away.

This is just my understanding so don't take it as absolute gosple. I know, I know Bernouli did his original studies with fluid dynamics, but it applies to fluid air as well. Think jet engine.



http://en.wikipedia.org/wiki/Bernoulli's_principle

 

[kirbysthebest]

Here is a really good article

It's mostly for central vacs, but the principal exists for portables as well.



http://www.canavac.com/page1.htm

 

[methodistbill]

Harley

That is a very good article. I appreciate all the input. I think that in the case of my Epic 6500, it wasn't working efficiently because the nozzle shoe wasn't making good contact with the floor. I gave it away, not realizing that it was something that might be fixable. Now I want to get it back and at least try and figure out how to fix it for the new owner! When I use my Kirby on bare floors, I can see it drawing debris from a few inches away. I always thought that was suction, but now I understand that good airflow has a lot do with it. And I really didn't think about it being designed to lift and vibrate the carpet! But I've noticed that happening! I try to follow Kirby's instructions about listening to the motor note when lowering the nozzle. On plush cut pile carpet it works fine. But I think the extra click is too much on my my loop carpet. The brush roll can just stop. But there's another thing I've noticed too. Use genuine Kirby belts! That helps a lot. Plus, I think it probably needs a brush roll with softer bristles on the loop carpet.

Bill

 

[kirbysthebest]

Bill

As Kirby says. Adjust the nozzle until the motor changes sound, then go one click more and you should be perfectly adjusted. This does not work, however, on glued down kitchen carpet. The machine just sucks tight to the carpet, it works better on tacked down carpeting that can be lifted.

This is why you will hear the stories when a carpet is being replaced and the installers will say "You have a Kirby don't you?" You will very rarely find fine sand under a carpet that has been regularly cleaned by a Kirby.

You are right about using genuine Kirby belts. I like the new ribbed/kurled belts. I think they are made from Kevalar. The really last and don't streach like the old rubber ones do.

 

[normvac]

It's all very basic, from my Kirby selling days. You put the
palm of your hand over the open end of a hose while the machine is on! Your hand is tight against the open end. That is
suction! If you start to pull your hand away and you hear the
air flowing. That's just what dose the cleaning, air flow.
Back in the 70's (kirby classic) Kirbys had an adjustable
vent on the top of the carpet cleaning head. So when you vacuumed glued down looped carpet. You would have air flow to
pick up the dirt !
Norm