Measuring air flow rates with different types of hoses hooked up to my shopvac and my dust collectors. What type of hose you use makes a big difference in terms of air flow. woodgears.ca/du...
What I love about you Matthias is that you set out to just build a new router table cabinet. You did that, it was done. Someone asked why not just use a shop vac and you took the time to explain why. And then, with no one asking, you decide to go deeper and explore suction power of a shop vac because your dust collecter preformed better than expected. So many would just take the W and move on, you were interested in why and took the time to show us. Thank you. Because frankly, you've already explored the advantages of why built in dust collection is the choice for you (frankly, suction is low on reason why I've done it to a few of my tools). So thank you. This feels like such old guard youtube. Not enough people do videos merely for experimentation especially when the topic has virtually no chance of going viral.
Couldn't agree more! I feel like RU-vid's structure and algorithms have pushed most RU-vidrs away from making quality content. It's really quite sad to see how many talented RU-vidr's skip out on making UNIQUE videos like this out of fear that RU-vid's algorithms will crush their subscriber or view counts.
See, these are the questions that I didn't realize I needed the answers to, but I'm really glad that I have them. These kinds of videos are super interesting to me, thanks for sharing.
This video should be required watching for any potential electrical engineering students. The analogies to current, voltage and resistance are just too perfect. Even the voltage drop on long thin gauge wires vs heavy gauge can be explained.
Electrical resistance analogy would also explain "what if we put a small section of smaller hose with a bigger hose?" type questions people are asking around here.
The smoothness of the inside of the hoses probably makes a big difference too, especially for smaller hoses where turbulence from the walls of the hose will take up a much larger part of the cross-section.
Thanks, Matthias, you've just convinced me that I did the right thing in buying a little shop vac to connect to the small hose on my ROS rather than using an adaptor to connect to the four inch hose on my big dust collector that I use for the thicknesser/planer and table saw, router, etc. It also has a power socket for the ROS (or Festool Domino) so I still get hands-free switch-on like on my big machines which are all supplied via a multiway socket connected to a vacuum auto switch box. I always thought that there was a reason why so much dust was present when I disconnected the four inch adaptor, and you have demonstrated the answer in another of your 'Investigative Science for Woodworkers' series.
Very similar to what we have to do for the Fire department. Using unique friction loss coefficients per hose diameter for a given length of hose, as well as accounting for miscellaneous in-line devices such as valves, wyes, fittings, we can then calculate total friction loss to determine which pump discharge pressure will be required to deliver the optimum nozzle pressure. Different nozzles (deck guns, smooth bore, & fog) have specific PSI and GPM ratings.
Hey MW, I'm standing up for the dust deputy which is in line with my shop vac. Although I might lose some efficiency with the airflow I gain usefulness as the vac works without clogging the filter for a significantly longer time. So, I'll take the losses for gains anytime. Keep making this type of content, it's so interesting. Cheers Joe from down under.
That's exactly what he says in the video. He says a shop vac only has a very small penalty when using a dust deputy cyclone....where a dust collector loses 50% when you add a cyclone. You hardly notice any difference when using a cyclone with a shop vac...it actually improves it in the long run because the filter doesn't get 90% of the debris.
I don't know why I haven't made this connection before, but watching you discuss the differences in your technique and the results gave me flashbacks to watching Doc Brown in Back to the Future. You are sort of a good guy mad scientist ...
It's exactly the same as designing a vacuum system for the lab - keep your connections as short and wide as possible. Bends are bad, too. And the smallest diameter in the system will throttle the entire system. Very interesting to see it in action. Thanks.
@John Ford, if you're running 6" diameter duct and taper it down in 4" diameter runs to your machines, will the whole system behave as though it is 4" duct, or will it be some intermediary between 4" and 6"?
@@Exodus5K it will be some intermediary, the section of 6" will count like a somewhat shorter section of 4". The shorter the 4" runs are in proportion, the more you will profit from the 6". Sadly the exact math is beyond me, but there are flow calculators online that may help.
John Ford: Very good recommendations overall... BUT one thing you have to add: An excessively large diameter can cause problems with heavier dusts collection, because a minimum velocity of the dust-ladden air is necessary in order to prevent dust settling. Some dusts can have a tendency to stick together or form agglomerates, with the result of partially clogging the hose or pipe. Therefore, some extra numbers are needed to best design the optimum diameter. In addition to that, the kind of hose corrugations has a large impact on pressure drop. So, for a complete design, some attention to the internal (lack of)smoothness of the hose is needed too. In my experience, the standard short radius PVC elbows are the worst; I learned how to bend PVC pipe into gradual large radius curves using hot sand and a hair drier, and improved my piping considerably! Best regards.
@@alfredomarquez9777 In wastewater collection this theory is called minimum scouring velocity. The idea is directly applicable here. Also, agreed on the consideration of smoothness of the interior of the hose/pipe as well as bends.
@@Exodus5K I'm not sure my vacuum line experience translates so directly to dust collection because we're in a different flow regime. But in a vacuum system a single small tube will reduce the flow in the entire system. Keep in mind that the vacuum systems I deal with are small (2 m total length, maybe) compared to a dust collection system. The real advice is to avoid sharp bends and narrow throttles.
I'm trying to cobble hoses to put a concrete shop vac outside and connect to a 7" dust shroud for an angle grinder with 7" diamond cup. Grinding concrete with regular shop vac captures most but not enough dangerous dust. This video perfectly explains why the small 1 1/8" shroud port is not adequate. Even with a 4 1/2" cup and smaller grinder it is barely adequate. Now time to use some ingenuity to get a better result. I have never subscribed before but you are now the first!
I wish more RU-vid videos were like this one. Why? For a start, no freak'n background music! Voice is clear and understandable! Camera is pointed 90% at the subject of discussion, not at somebody's yapping face! It gets to the point! No time-lapsed assembly ad nauseam! Good video.
Great tip. I recently added a Dustopper to my shop vac based dust collection but the airflow was terrible and it also wasn't separating well. The issue turned out to be the 1 1/4" hose which came with the shop vac. Swapping with a 2 1/2" hose made a huge difference in suction (so far only assuming the issues with the dust separation were due to the low airflow).
very useful! it is hard to understand all the different information out there about different vacuum types (shop-vac vs. dust collectors), hose types, etc. Nice to see it all presented in one practical use. Would love to have more insight in the future about why we use both types of vacuums in a workspace.
higher velocities = higher pressure closer tolerances = higher pressure larger blade area = larger volume pressure x volume = power small blade + high rpm = high pressure large blade + low rpm = large volume large blade + high rpm = large volume @ high pressure = tons of power
@@LateNightHacks does blade shape have any impact that you are aware of? So in other words, assuming no design errors a simple back curved fan blade could be made to a shorter height and larger diameter and spun with a higher 3600 RPM to get more static pressure? Meanwhile a taller fan assembly spun at 1700rpm would be quieter and probably provide more airflow but at a lower SP?
I have the same craftex dust collector. I noticed a huge performance boost when I increased all my hoses to 4". I use a Veritas cyclone lid that fits over a garbage can and has 4" hose connections. I still get good flow with this. I haven't measured the flow, but it gets all the shavings from my planer. My old setup was a shop vac with 2.5 inch hoses and a dust deputy cyclone. This did not work well at all when I swapped the shopvac to the craftex, but the 4" hoses made a huge difference.
BUT >> High Flow Rate with Low air velocity will not carry chips thru the hose. / / / So it would seem you have only done a wonderful job of starting the investigation into a fascinating and important topic "Things that Suck". / / / What Velocity is required to move objects of different sizes . . . . the small hose on your small Shop-Vac will pull a marble uphill . . . . not so much with the bigger hose. . . . . GREAT STUFF !
You probably have a point but I would argue that with dust / chips it is mostly self correcting. Imagine a hose with a thin buildup of dust along the bottom Now imagine that the buildup grows to the point that the cross section is cut in half, meaning the velocity goes up by double. Now there is enough velocity to pull the chips and dust out and you get a "dam" of sorts that runs thru the hose and clears it out. Then the cycle repeats
Thank you for this clear and in-depth exploration of the effects of different hoses and cyclone add-ons. I’ve been trying to decide on an approach to dust collection in my small shop and this analysis will be a factor in my design.
Thanks for the video. I have known the smaller shop vac hoses were not good for air flow compared to the 2 1/2in hose. I appreciate you spending the time to show the measurements. I do not have an airflow meter. The flexible hoses have a lot more pressure drop than if they were smooth on the inside, but we all need to be able to easily flex our hoses around the shop. I was expecting the cyclone to have a larger impact. Interesting. Dave.
@@GreenAppelPie You can bet anybody taking science classes like chemistry and physics will learn it. And science and engineering is where it shines so that makes sense. I don't want to be buying 229mm pies. I see a place for both systems at this time.
Thank you, I've learnt a lot from this... Bought 10m hose online, connected it between my belt sander and a domestic vacuum cleaner, then wondered why most of the dust was escaping from the joint between the hose and sander... Now I know why!! (Yes I'm going to shorten the hose and buy a shop vacuum when I get around to it!)
Thanks for taking the time to experiment on this! Very useful data that will help us take better decisions on our dust collection setup! Really appreciated! Cheers!!
A great visualization of fluid dynamics! Thanks! Before the Internet, we used to use Thomas Glover's Pocket Ref to get the flow rate drops in plastic pipe so we'd know the right size pipes to use in moving water for our rainwater and orchard systems. Now it's easy to look up online though.
I have a 2000 watt shop vac with a 2"hose.Found out the first time it clogged that it fitted onto a 1" pipe into the vac body.Made a few adjustments and now it can lift anything put in front of it.
I think you are right about the cyclone penalty being more for a high-flow system, because it results from accelerating the air to make it spin, and there's more air to accelerate. In a small DC like your craftex, putting a Thein baffle inside (rather than free standing) may cost the least flow because the air already circulates there, and you are simply using that circulation more effectively.
I have a background in chemical engineering. Some other things for you to look into is Slot Velocity, Particle Carry Velocity, and Head loss via hose texture.
I’ve made a DIY shop VAC with a vacuum motor (included fan and speed controlling circuit) with bigger air hoses and 2 stage filters (cyclone and paper filters) and it works very well. The old vacuum machine didn’t work well by household design’s on/off button.
Thanks. I was going to use a cyclone and pool hose with a vacuum but recently wondered if a dust collector would be better. Turns out that would be a waste of money and a step backwards. Great video.
Thank you. I have just been wondering if I would get better results with a bigger hose and you have saved me the effort of experimenting. I will buy you a beer next time you are in Melbourne , Australia
On an older 1HP dust collector, I added extensions to the vanes on the impeller. That dramatically increased the static pressure. I was then able to use smaller hoses and still get a decent CFM. However, the one major drawback of the vane extensions was that a massive increase in the noise the tool made. It was very high pitched sound, which the family told me was unsuitable for my basement shop
Enjoyed a lot- Also like the text-over to admit that the people will doubt basic physics ;-) . Checking the effect of bends vs straight tube would be intersting
Well, another aspect of CFM is the sustained force that a motor has behind the volume of air being moved, which is often not considered but can be the most important part of pulling things into an opening or being able to pick something up. My shop vac has around 150 CFM, but a low amount of sustained suction, so it cannot hold a candle to some other vacuums out there. I worked a job where we had a truck mounted tri-lobal vacuum, running on the PTO of the truck. It could pick up carpet off the carpet tacks, or pull a baseball all the way into the reclamation tank! it only had 200-220 CFM, but holy crap it never lowered in pulling power even when the opening was made smaller, it just pulled harder.
Re: the airflow drop due to cyclone - it’s worth keeping in mind that in practice, the cyclone will keep your filters much cleaner so your effective penalty might be significantly less than it seems when testing with a clean filter. 🤓
I am amazed the industrial dust collector has less suction than a shop vac! In my shop I have 8 shop vacs on my machines wired to go on when I turn the machine on. Not exactly ideal but pretty good. I have an old furnace fan on the ceiling the has 2- filters for air filtration, again Ok but not ideal. I really like your dust collector set-up and may convert some of my machines to it especially the sanding machines. Thank You for all you have given me!
I'm surprised you didn't extrapolate further with the shop vac to see if it would benefit from an even larger hose, or what the break even point in hose diameter may be in pressure/CFM.
Sounds like you would be better off sticking with the cyclone and shop vac on your short hose. Maybe that's why she left in fact. Sorry bro, couldn't resist. Your comment made me laugh. 😂🤣😂👍👌
First thanks for all your videos. My question is have you or have you heard of anyone trying to increase the size of the inlet right at the source? Let’s say on a shop vac. Going from the 2” to a 3 or 4”. And then also some how increasing the size of the filter area or even eliminating the internal filter in the shop vac and putting one larger one externally? Let me know. Thanks again for all you do for the woodworking community.
I once tried swimming pool hose, glued the coupler on friday and monday I stepped on the switch on the vac and lost it as a disorienting squeal built up till I could stop the vac. The wavy inside was causing harmonics way up the scale and piercing sound. Hook up a bunch if you want to make a burglar chaser when they break in. Like an elk bugleing the wind pipe is ridged. That is how the sound is made. If hoses make that sound it's bound to be a loss of flow. I took 20 feet of that hose at a street party and had everybody stand back as I whirled the hose around overhead. Strange sounds softly filled the whole street as a giant Leslie speaker or UFO hovered above us.
Hi Matthias, excellent video. Hope you still monitor these old comments.. I feel the there needs to be another layer of analysis added here: what is the air velocity per pipe per machine, because surely that is the fundamental physics that drives dust or chip movement in the hose? You can maximize volumetric flowrate by increasing the pipe diameter to where you basically have no losses in the pipe, but you'll also have (near) zero velocity and no chip/dust movement. Air speed transports particulates, not pressure or CFM's.. But you know that. Then you'll have to test/experiment to determine min velocity required to say lift/suspend a typical planer chip vertically as baseline for comparison... Good luck!
A lot of people add cyclones to their dust collector like your big one. But they use much bigger cyclones than your homemade cyclone, so the CFM penalty is much less severe. Just remember that larger CFM requires a larger cyclone.
The ripples create eddy currents which keep dust moving along.A smooth hose would work better on large particles but all the really small stuff would start to build up due to static.
They would collapse and kink unless they're really beefy so they get pretty expensive. Or you have to go with a fixed, rigid system like pvc pipe. It's pretty cost prohibitive or impractical in most home shops.
First thing I thought of. I have similar ideas to other commenters here, but he does have a rigid metal duct pipe connected to some equipment (even visible in this video) so could possibly fairly easily do a comparison there as well.
Awesome what knowledge can be gained from a little effort. Much appreciated! I would luv to know how this stacks up to strait pvc pipe plumbed in with blast gates 45 degree bends etc...
I'm having trouble understanding how this doesn't break Bernoulli's Principle, I'm assuming there's some losses due to turbulence/friction in the tube, but this substantial?
Great work. After your last video I had a lot of curiosities regarding the relative performance of store-bought dust extractors using consistent methodology. You have not disappointed.
Thanks for the “dust lab” trials! May have already been mentioned, but look up cyclone design by Bill Pence, (iirc) did fabulous engineering whilst recovering in hospital from shop dust caused lung problems. Wizard stuff. If you’re already familiar with his work, my bad!
Matthias: Thanks again and again for another great video, I suspect you are a "Natural born engineer"! One humble suggestion I would make to you is in regards to optimum hose or pipe diameters.- Very good recommendations overall... BUT one thing you may want to add: An excessively large diameter can cause problems with heavier dusts collection, because a minimum velocity of the dust-ladden air is necessary in order to prevent dust settling. Some dusts can have a tendency to stick together or form agglomerates, with the result of partially clogging the hose or pipe. Therefore, some extra numbers are needed to best design the optimum diameter. In addition to that, the kind of hose corrugations has a large impact on pressure drop. So, for a complete design, some attention to the internal (lack of)smoothness of the hose is needed too. In my experience, the standard short radius PVC elbows are the worst; I learned how to bend PVC pipe into gradual large radius curves using hot sand and a hair drier, and improved my piping considerably! Best regards from México.
What’s REALLY interesting is when you increase the hose diameter, the shop vac intake size never changes. Seems like there would be a limit from the size of said intake diameter...I wonder what the numbers would if you introduced water to a wet/dry vac. Not sure how you’d test it🤷🏻♂️
Oh! So I would be better much off replacing my standard, narrow and long, shop vac hose for a 2 1/2 inch hose that is considerably shorter. Glad I found this now, as I am just planning to upgrade my workshop extraction capabilities. On the other hand, would it still provide the fast air speed recommended for hand power tools though?
