Direct Air vs Bypass Air confusion
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I don't have a Dyson, I'm just not a fan of bagless vacuums, too messy to empty and the filters clog very quickly, but from what I have heard, the Dyson vacuums have a lot of suction, but not very much airflow. So, if you put your hand against the hose, it might feel very strong, but would you feel any air if you were a couple inches away? I do have a Miele C1 olympus canister, the airflow is very good, and the suction is decent.
I don't have a Dyson, I'm just not a fan of bagless vacuums, too messy to empty and the filters clog very quickly, but from what I have heard, the Dyson vacuums have a lot of suction, but not very much airflow. So, if you put your hand against the hose, it might feel very strong, but would you feel any air if you were a couple inches away? I do have a Miele C1 olympus canister, the airflow is very good, and the suction is decent.
anontemp123
Active member
Airflow, agitation, suction
To a novice like me, suction seems like the most important. Even after developing a (basic) understanding of suction, I am surprised it's third on the list for deep cleaning, after airflow and agitation. I am not doubting it at all, but I am looking for more sources. When searching Google, I end up with results for Vacuumland and other enthusiast sites, as well as some commercial sites. Offhand, does anyone have a link for someplace more, I don't know, "independent" or specifically discussing the science behind it?
To a novice like me, suction seems like the most important. Even after developing a (basic) understanding of suction, I am surprised it's third on the list for deep cleaning, after airflow and agitation. I am not doubting it at all, but I am looking for more sources. When searching Google, I end up with results for Vacuumland and other enthusiast sites, as well as some commercial sites. Offhand, does anyone have a link for someplace more, I don't know, "independent" or specifically discussing the science behind it?
kirbysthebest
Well-known member
I don't know of any more independent sites. You may search "Suction vs Air-flow" also "air watts" you will find many articles, most from either sites like this one, or vacuum sales. More scientifically you may look at the principals of vacuum, and How it works.
The correlation of agitation and air-flow have been long established in the vacuum industry back with Mr. Spangler first attached a pillow case to a broom stick and a fan.
"It beats. . .as it sweeps. . .as it cleans" as Hoover demonstrated, It lifts the carpet slightly off the floor, it beats the dirt lose from the nap of the carpet and the air-flow carries it away. You do need the suction to lift the carpet, and the vibration to loosen the debris, but the air-flow is what gets it out of the way as the nozzle moves across the surface. Some modern machines don't rely so much on the suction, or the lifting of the carpet. They depend more on beating the heck out of the carpet and letting the air current take it away.
(Added) If you have too strong suction, it will seal off and you will reduce airflow. There will still be some cleaning, but less because the debris is not being carried away.
Other than gimmicky type things with vibrating plates and ultra violet lights the cleaning principal has been pretty much perfected and most of the focus within the last couple of decades are more on the capture systems the vacuum possesses.
[this post was last edited: 11/8/2016-12:16]
http://home.howstuffworks.com/vacuum-cleaner.htm
The correlation of agitation and air-flow have been long established in the vacuum industry back with Mr. Spangler first attached a pillow case to a broom stick and a fan.
"It beats. . .as it sweeps. . .as it cleans" as Hoover demonstrated, It lifts the carpet slightly off the floor, it beats the dirt lose from the nap of the carpet and the air-flow carries it away. You do need the suction to lift the carpet, and the vibration to loosen the debris, but the air-flow is what gets it out of the way as the nozzle moves across the surface. Some modern machines don't rely so much on the suction, or the lifting of the carpet. They depend more on beating the heck out of the carpet and letting the air current take it away.
(Added) If you have too strong suction, it will seal off and you will reduce airflow. There will still be some cleaning, but less because the debris is not being carried away.
Other than gimmicky type things with vibrating plates and ultra violet lights the cleaning principal has been pretty much perfected and most of the focus within the last couple of decades are more on the capture systems the vacuum possesses.
[this post was last edited: 11/8/2016-12:16]
http://home.howstuffworks.com/vacuum-cleaner.htm
sptyks
Well-known member
Anontemp123,
I don't understand why you are still confused about suction and airflow. Have you watched all of the videos and carefully read the written responses to your questions? I don't know where you could look for additional info on this subject that would give you more detail than the descriptions given here.
I doubt you will find a better description of suction vs airflow anywhere than from the experts here at Vacuumland. Many of the guys that have given descriptions and advice on this particular thread have been working with various types of vacuum cleaners for many years. Some own or have owned their own vacuum cleaner shops. Everyone has a particular brand or type of vacuum cleaner that they are fond of, but one thing they all have in common is their vast knowledge of how a vacuum cleaner works and the principles of suction vs airflow and agitation.
I don't understand why you are still confused about suction and airflow. Have you watched all of the videos and carefully read the written responses to your questions? I don't know where you could look for additional info on this subject that would give you more detail than the descriptions given here.
I doubt you will find a better description of suction vs airflow anywhere than from the experts here at Vacuumland. Many of the guys that have given descriptions and advice on this particular thread have been working with various types of vacuum cleaners for many years. Some own or have owned their own vacuum cleaner shops. Everyone has a particular brand or type of vacuum cleaner that they are fond of, but one thing they all have in common is their vast knowledge of how a vacuum cleaner works and the principles of suction vs airflow and agitation.
anontemp123
Active member
I'm not the sharpest tool in the shed. I am not confused about suction and airflow any longer. Before I conflated suction and airflow to mean the same thing. From the videos and explanations, I could clearly see these were different, yet complimentary, things. Airflow was easy for me to understand. I never understood pressure -- no idea what the weatherman means when he says "high pressure system" -- so it took a while for me to really get a grip on suction. The explanations really helped with that.
I have the utmost respect for professionals and hobbyists who share their knowledge and experience in their spare time. It is enough for me to read something here and believe it even before I understand it. But before I spread the vacuum gospel, I wanted to check if there were other sources because a forum is not always the easiest source to give someone.
I have the utmost respect for professionals and hobbyists who share their knowledge and experience in their spare time. It is enough for me to read something here and believe it even before I understand it. But before I spread the vacuum gospel, I wanted to check if there were other sources because a forum is not always the easiest source to give someone.
sptyks
Well-known member
Definition of Suction per Wikipedia :
Suction is the flow of a fluid into a partial vacuum or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust is "sucked" into a vacuum cleaner when it is pushed in by the higher pressure air on the outside of the cleaner. The higher pressure of the surrounding fluid can push matter into a vacuum but a vacuum cannot attract matter.
Suction is the flow of a fluid into a partial vacuum or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust is "sucked" into a vacuum cleaner when it is pushed in by the higher pressure air on the outside of the cleaner. The higher pressure of the surrounding fluid can push matter into a vacuum but a vacuum cannot attract matter.
anontemp123
Active member
I remember first time I read that on Wikipedia, the term "fluid" threw me for a loop. I had forgotten the scientific definition of a fluid.
As far as Kirby vacuums exhausting unfiltered (carbon-containing) air used to cool the motor, how about when the air is brought in? Is it filtered as it is brought in to cool the motor? Does cooling a motor with "dirty" air affect its longevity?
As far as Kirby vacuums exhausting unfiltered (carbon-containing) air used to cool the motor, how about when the air is brought in? Is it filtered as it is brought in to cool the motor? Does cooling a motor with "dirty" air affect its longevity?
kirbysthebest
Well-known member
Unfiltered cooling air.
If you are running in an extremely dirty condition, or in the case where using powdered carpet freshener, it could shorten the motor's longevity. There are, however, Kirbys of vintage age that are still running with their original innards.
If you are running in an extremely dirty condition, or in the case where using powdered carpet freshener, it could shorten the motor's longevity. There are, however, Kirbys of vintage age that are still running with their original innards.
sptyks
Well-known member
The Kirby's cooling fan emits a minute amount of microscopic carbon particles from the motor's carbon brushes, I mean we're talking a couple of parts per million (PPM ) a second. This is an <span style="text-decoration: underline; background-color: #ffff00;"><span style="font-size: 14pt;">insignificant </span></span>amount of particulate matter so it would be a waste of money to put a filter here. No one is allergic to carbon. Because our bodies are mostly made up of carbon.
Bypass air vacuums use a filter for air exiting the motor because they use the<span style="font-size: 14pt; background-color: #ffff00;"> high volume</span> of air exiting the bag to cool the motor so there is a great deal more carbon in this airstream. Direct air vacuums use a separate small fan to cool the motor so there is<span style="font-size: 14pt; background-color: #ffff00;"> much less volume </span>here and a filter in this location would block air needed to cool the motor.
If you pause this video at 1:10 you should see the small motor cooling fan located directly behind the main suction fan. It doesn't show here but these two fans are completely sealed off from each other.
If you watch the first 35 seconds of this video, you will see how the cooling fan is separated from the main fan:
[this post was last edited: 11/9/2016-17:23]
Bypass air vacuums use a filter for air exiting the motor because they use the<span style="font-size: 14pt; background-color: #ffff00;"> high volume</span> of air exiting the bag to cool the motor so there is a great deal more carbon in this airstream. Direct air vacuums use a separate small fan to cool the motor so there is<span style="font-size: 14pt; background-color: #ffff00;"> much less volume </span>here and a filter in this location would block air needed to cool the motor.
If you pause this video at 1:10 you should see the small motor cooling fan located directly behind the main suction fan. It doesn't show here but these two fans are completely sealed off from each other.
If you watch the first 35 seconds of this video, you will see how the cooling fan is separated from the main fan:
[this post was last edited: 11/9/2016-17:23]
anontemp123
Active member
Summary of what I have learned
Thank you everyone for the education. Here is a summary:
Fan placement matters for airflow. The longer and more crooked the path, the less the airflow. In a well sealed system, however, suction is not affected by fan placement.
Vacuum fans are driven by motors. Motors get hot and need to be cooled.
Bypass vacuums can be said to have better filtration because the air brought in with vacuumed debris, after filtration via bag or filter, can then be used to cool the motor. This is because the bag/filter is in front of the fan/motor. That air is sometimes filtered again before being exhausted, although the benefit of filtering carbon particles given off by the motor is debatable. Regardless, all air that goes into a bypass vacuum comes out cleaner than it went in, hence a bypass vacuum “filters the air around you.” Contrast this with direct air vacuums, where air brought in to cool the fan motor is exhausted unfiltered and is separate from air brought in with debris. Hence bypass vacuums can be said to have better filtration. (I am unsure why motor cooling air in direct air vacuums can’t easily be filtered.)
Metal and wooden brushrolls are both okay. Beater bars were removed from brushrolls because users were damaging hardwood floors. (I think "bearings" keep the brushroll balanced, but not 100% sure.)
For agitation, all you need is for the brush tips on your brush roll to touch the top of your carpet.
You can maintain a specific amount of suction with very little airflow. Therefore the claim of “never loses suction” is very misleading. Airflow is equally important in both direct air and bypass machines. Suction, however, is much more important in bypass systems. In bypass systems, suction is bringing in the air, but without enough airflow to actually carry the debris, you cannot clean.
Thank you everyone for the education. Here is a summary:
Fan placement matters for airflow. The longer and more crooked the path, the less the airflow. In a well sealed system, however, suction is not affected by fan placement.
Vacuum fans are driven by motors. Motors get hot and need to be cooled.
Bypass vacuums can be said to have better filtration because the air brought in with vacuumed debris, after filtration via bag or filter, can then be used to cool the motor. This is because the bag/filter is in front of the fan/motor. That air is sometimes filtered again before being exhausted, although the benefit of filtering carbon particles given off by the motor is debatable. Regardless, all air that goes into a bypass vacuum comes out cleaner than it went in, hence a bypass vacuum “filters the air around you.” Contrast this with direct air vacuums, where air brought in to cool the fan motor is exhausted unfiltered and is separate from air brought in with debris. Hence bypass vacuums can be said to have better filtration. (I am unsure why motor cooling air in direct air vacuums can’t easily be filtered.)
Metal and wooden brushrolls are both okay. Beater bars were removed from brushrolls because users were damaging hardwood floors. (I think "bearings" keep the brushroll balanced, but not 100% sure.)
For agitation, all you need is for the brush tips on your brush roll to touch the top of your carpet.
You can maintain a specific amount of suction with very little airflow. Therefore the claim of “never loses suction” is very misleading. Airflow is equally important in both direct air and bypass machines. Suction, however, is much more important in bypass systems. In bypass systems, suction is bringing in the air, but without enough airflow to actually carry the debris, you cannot clean.
sptyks
Well-known member
You passed!
Congratulations Anontemp you passed the test. You now have all the knowledge you need to make an educated decision on what type of vacuum would best suit your needs.
Regarding the topic of cooling fan exhaust on Direct air vacuums: The small cooling fan does not produce enough airflow or positive pressure to force the air through a filter. So if you put a filter on, there would not be enough airflow to cool the motor properly therefore the motor would soon overheat and burn out.
Congratulations Anontemp you passed the test. You now have all the knowledge you need to make an educated decision on what type of vacuum would best suit your needs.
Regarding the topic of cooling fan exhaust on Direct air vacuums: The small cooling fan does not produce enough airflow or positive pressure to force the air through a filter. So if you put a filter on, there would not be enough airflow to cool the motor properly therefore the motor would soon overheat and burn out.
eurekaprince
Well-known member
I still say that fan-first uprights with top fill dust bags filter air better. The dirt falls away from the path of the air and so is left undisturbed. With bag-first uprights and canisters, air is constantly fighting its way through the pile of dirt in the bag and even the best filtering canisters give off a dusty smell for a few seconds after the machine is turned on because the sudden rush of air into the bag kicks up the entire pack of dirt in the bag.
sptyks
Well-known member
Brian, I agree with you 100%. Most people don't stop to think about how the air passes through the bag.
Kirby and Royal Direct air vacuums leave the top half of the bag empty so the air exits up there rather than being drawn down through all the dirt in the bottom of the bag as it does in most Bypass air machines.
Kirby and Royal Direct air vacuums leave the top half of the bag empty so the air exits up there rather than being drawn down through all the dirt in the bottom of the bag as it does in most Bypass air machines.
Well in the case of a Compact-TriStar the air goes Over the bag, but catches dust and dirt. You never once lose suction. I use one for a shop vac and bench vac and I have to check the bags as the suction is always constant
Andy
Andy
bipass motors
Another place where bypass motors are used is in wet dry vacs, carpet extractors, or any other machine that can vacuum up liquids. A flow through motor would not work here since vacuuming up liquids would pull the liquid through the motor and ruin it. This is why all motors in these kinds of vacuums also have a separate cooling fan. This is also why most of these machines have some kind of float device that either shuts off the suction or turns the machine off completely when the tank is full, otherwise the liquid would be sucked through the motor. Actually, I don't think the rainbow or sirena has this, I assume if the basin gets too full, the separator will still keep the water out but not sure.
Another place where bypass motors are used is in wet dry vacs, carpet extractors, or any other machine that can vacuum up liquids. A flow through motor would not work here since vacuuming up liquids would pull the liquid through the motor and ruin it. This is why all motors in these kinds of vacuums also have a separate cooling fan. This is also why most of these machines have some kind of float device that either shuts off the suction or turns the machine off completely when the tank is full, otherwise the liquid would be sucked through the motor. Actually, I don't think the rainbow or sirena has this, I assume if the basin gets too full, the separator will still keep the water out but not sure.
anontemp123
Active member
What personally tripped me up the most was thinking of airflow, agitation, and suction as independent entities, when really all three are working together. And depending on context, a term like "agitation" can include: suction lifting the carpet, the brushroll hitting the tips of the carpet, and then airflow lifting the debris. Then, I was getting caught up in which is more important than the other without a good enough understanding of these principles. And all three play key roles anyway -- even with direct air vacuums, suction is lifting the carpet for you -- so for the novice it's probably best not to get into which of the three is more important (leave that to you experts).
As far as understanding suction, or pressure in general, you all must've really paid attention in science class. Over the last few days, I randomly asked 10 friends and family members about their understanding of pressure. Eight admitted they really don't know what pressure is. All 10 have at least a bachelor's degree. It's possible airflow vs suction is more confusing for the average person than you might think. There's a video on YouTube (I can't find at the moment) where a shop owner is measuring suction on a clogged vacuum vs an unclogged vacuum. Both have the same reading on the pressure gauge, but obviously the lack of airflow affects the clogged one. That video helped me finally start making sense of the explanations that were written here. And it made me remember all the instances over the past decade when I couldn't figure out that my Dyson felt like it had good suction when I would put the hose against my hand, but I had to clean the bin and filter to get it working 100% again.
I also wanted to comment on a couple posts I read on this site and elsewhere. The authors of these posts made snide remarks about how "they're just vacuums", or "don't you have anything better to do than debate bypass vs direct", etc. I wish I could ask these folks, why the heck are you at vacuumland.org? This isn't mildinterestinvacuums.com! Even I don't understand why you have so much fun talking about vacuums, but so what, I appreciate the passion. In forums for my personal hobbies, I love getting worked up about things, have virtual frenemies, and all the rest of the drama. I don't know why, but it always gets under my skin when folks go into others' playgrounds and say stuff like that. Especially a "playground" that is the most valuable resource for vacuum knowledge on the Internet.
As far as understanding suction, or pressure in general, you all must've really paid attention in science class. Over the last few days, I randomly asked 10 friends and family members about their understanding of pressure. Eight admitted they really don't know what pressure is. All 10 have at least a bachelor's degree. It's possible airflow vs suction is more confusing for the average person than you might think. There's a video on YouTube (I can't find at the moment) where a shop owner is measuring suction on a clogged vacuum vs an unclogged vacuum. Both have the same reading on the pressure gauge, but obviously the lack of airflow affects the clogged one. That video helped me finally start making sense of the explanations that were written here. And it made me remember all the instances over the past decade when I couldn't figure out that my Dyson felt like it had good suction when I would put the hose against my hand, but I had to clean the bin and filter to get it working 100% again.
I also wanted to comment on a couple posts I read on this site and elsewhere. The authors of these posts made snide remarks about how "they're just vacuums", or "don't you have anything better to do than debate bypass vs direct", etc. I wish I could ask these folks, why the heck are you at vacuumland.org? This isn't mildinterestinvacuums.com! Even I don't understand why you have so much fun talking about vacuums, but so what, I appreciate the passion. In forums for my personal hobbies, I love getting worked up about things, have virtual frenemies, and all the rest of the drama. I don't know why, but it always gets under my skin when folks go into others' playgrounds and say stuff like that. Especially a "playground" that is the most valuable resource for vacuum knowledge on the Internet.
anontemp123
Active member
Update, 4 years later
I ended up purchasing a used Kirby on eBay and love it. It hasn't given me any trouble in almost 4 years. For hardwood, I use the floor attachment that came with our old Dyson DC14. I've been using a cordless V8 Animal daily for a couple weeks now (at someone else's house) and I like how light and maneuverable it is. The V8 is very annoying to clean, though. It seems like the V8 relies mostly on agitation to get the job done; the V8's non-powered attachments don't work that well.
I ended up purchasing a used Kirby on eBay and love it. It hasn't given me any trouble in almost 4 years. For hardwood, I use the floor attachment that came with our old Dyson DC14. I've been using a cordless V8 Animal daily for a couple weeks now (at someone else's house) and I like how light and maneuverable it is. The V8 is very annoying to clean, though. It seems like the V8 relies mostly on agitation to get the job done; the V8's non-powered attachments don't work that well.
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