Why are CFM ratings BS?
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- เผยแพร่เมื่อ 2 มิ.ย. 2024
- Why won't your compressor keep up with a small air tool? Because the CFM ratings are taken at the suction INLET of the compressor, not the pressurized air from the tank. I'll show you how a Rolair compressor rated at 4.1CFM @ 90 PSI only really delivers 0.9CFM @ 90PSI of useable air.
- วิทยาศาสตร์และเทคโนโลยี
The new standard shall be known as AVE: Actual Volume Expelled
Best comment
But the needle DOES settle at 55psi after the CFM guage gets to the desired 3.5-ish CFM level, so assuming the tool is spinning at full RPM's (no-load), plus this chuck is heavier than the original collet, there's a small tool in and the bearings aren't new, so I'm assuming 32-34k RPM's, then if the needle isn't dropping (even when the tank empties and the compressor motor kicks on), then where's the problem...? The needle's staying, ya?
yes and it will only be used in canada
@@timmarrier wtf are you going to do with a tool that can run continuously, but only at no load?
@@kgchrome both but remember its only valid in canada the usa will be scared of it just like metric
SCFM = Standard Customers Fooled per Minute. THX AVE. Good Explanation.
per Mention*
@@totally_not_a_bot TOUCHE`
😂 Ave better like this comment its a gooden.
The C stands for something different in Australia
I think the other F word is better here.
What caused me to notice this was pricing air compressors for work. Go to an online industrial supplier and an 18 cfm compressor is $2,500-$4,000. Go to a local hardware store and a similarly rated compressor is $600-$900.
Hardware stores are trying to say their $600 compressor out-competes one costing at least 2 grand more, SURE it does.
Ironically this made me extremely wary about buying the cheaper compressor, likely the opposite effect the marketing department wanted.
Just get you a compressor pump from the industrial place and use a 5 or 6 horsepower lawn mower engine on it to run it. If you already have a tank that can be used you can get a decent cfm pump for a couple or few hundred. And a 6 hp lawn mower motor from harbor freight or a dead generator or rebuild one for pennies to power it. I run a parallel set up. I run 3 110v compressors on separate breakers on a 1 to 3 reversed and plug the 3 lines into one lowes air tank. I get 65 gallons of 150psi air and 6.8peak horsepower. And I use them to paint. And usually the 3rd one doesnt kick on often. I can paint a car non stop with that set up. Made my own dessicant filter. People get rid of compressors cheap on craigslist
That's kinda like saying "Our power supply can deliver 1,000,000 amps at 0V into 1nano-ohm"
or giving the specifications of a steput transformer as 2.4kV @ 10A
(volts output, amps input)
instead of input 240V @ 10A
output 2.4kV @ 1A
They do that on those USB power banks. They quote the output voltage at 5 V but put the amp hour rating of the 3.7 V lithium pack, so you multiply them both together to get the watt-hour rating and it's way higher than it actually is.
im literally speechless. went and looked up my husky 60 gallon and in the description is talks all about just CFM but you dive deep into the specs and they have hidden the Scfm. bastards. Grab your pitchforks folks
My rule of thumb.... Read compressor rating.. divide by 6, equals approximate real capability.
Yep, that's close to 100% duty cycle for tools rated @ 90psi. If you're using chisels for stone work so you can get away with 50% duty cycle (5s work, 5s taking a look at what you've done), you can divide compressor's declared (s)cfm rating by 3. Which makes cheap compressor absolutely useless for most tools.
Hmm...
I'm so angry I could spit!
Hey, remember that thing for the thing? Just waiting on you to send the fusion model and I'll beep boop the dashes and dots into the wunderbot and poop out some parts for you.
do it then
Sir, I tip my lid to you.
Like so many others I have struggled to understand why the heck our compressors (even trade quality name brand 12-18CFM ones) could never keep up with basic tools. This here is the definitive answer and I am about to go postal at our tool reps as they continually lied to us when we queried this problem, always blaming regs, tool quality, power supply, filters etc. I had tried an air flow meter just like you did and had proved this flow issue but could never work out the correlation between what I saw and what they rated because, unlike you, I never did a release to atmosphere flow test... seems so obvious now but I missed it.
There will be a couple of reps getting a roasting in the coming weeks as I reproduce this test in front of them and prove that their assurances of "real working pressure CFM ratings" have been complete and utter BS.
Excellent! Have you done this yet, and if so what was the outcome?
ya! a follow up would be greatly appreciated
Tell us please
You think the compressor can handle multiple tools at once??? Jeez, what happened to America smarts?? You run a number of tools on a home depot little compressor, gee, the tools won't work well. This is so amazing.
Inquiring minds want to know. Did you roast the tool men? Or did they conk you on the head with a wrench and cast your body behind the tool bench
I always knew those rating were BS in some capacity. I didn't know to what extent though. Jesus Christ. Certainly explains why my compressor is running all the damn time just working on my cars.
I hope this video makes the rounds and gets some manufacturers beat up at least a little. Or at least starts a wider conversation. The more folks that find this one from searches on the topic, the better. Great video.
Hey hey now, Jesus had nothing to do with this lol just seems he gets the blame every time something unexpected happens lol
I find this funny too because when I bought my compressor it was rated on the output, both at 40 PSI and 90 PSI. And it has proven that it can keep up with a tool that runs less than the 5.5 CFM at 90 PSI. It was the only compressor in the store that was rated at a certain pressure output, not the suction volume input.
@@chubbysumo2230 Was it listed as SCFM or ACFM? A is for actual s is crap and is just momentary like AVE has shown.
@@chubbysumo2230 chubbysumo. What a name. Lol. At least you didn't go for something like "the chubbiest sumo" or "the chubbiest sumo all the time". Lol
@Johan Fouche I've actually encountered folks that were convinced that their car sound system was delivering 50000WRMS as rated...lol. I sat them down and as gently as humanly possible introduced them to ohm's law... and then asked them to look up the maximum amperage their alternators and batteries could deliver and sat back and waited for the penny to drop...lol
I almost wish, that I hadn’t watched this....
I always expect manufacturers to fudge the numbers, a bit, but I never expected anything this bad. This is damn near criminal.
it is criminal
Why? They are building air compressors that work for lower pressure single use only!! You can't get the pressure you want because you want it!!!
@@duanelohr1869 It's criminal because they say "at 90 PSI or at 40 PSI", clearly implying that the CFM is in some way comparable to the CFM used by your air tool. The fact that (arguably) intelligent users like us (at least this channel's producer) didn't know that in reality the numbers are only off by about 1/10 the amount before is proof that it is deceptive.
@@DellAnderson you still don't understand. If you are working with a 90 cfm tool on a 90 cfm air compressor, you get one shot per minute. Hardly worth it. The 90 cfm was designed to work with Lower powered tools. 45 cfm tools are marginal. If you want the right compressor vs. The tools you want to use, then upgrade your compressor. Don't blame companies for your lack of knowledge.
@@duanelohr1869 I think you are the one getting a bit confused. I think you're mixing up cfm and psi. A 90 cfm compressor would be pretty huge.
I've learned more from this channel than I did in all of high school
A long time ago a grey beard told me that compressors were rated at atmospheric pressure, not stated pressure. I didn’t believe him until today.
I ran this test this weekend. I have a husky 30gal belt drive compressor, rated at delivery 5.3cfm@90psi. started at 150psi. Ran my hf die grinder rated at 3cfm. Compressor could only maintain 50psi after a few min of use. Wouldn't drop below 5psi, but the tool was running poorly. Great job on getting the word out on the deception.
wayne light
Thanks for testing and posting. I mean it.
But how come you haven’t noticed this before? I’m asking in all seriousness. Tia
@@Conservator. it was the first time I've used my die grinder at home and not at work.
At work we have 2 scroll style compressors feeding a 200gal tank with a 120cfm dryer. You get spoiled on things like that
There is fuckery in the tool consumption ratings too..if you read the fine print for the die grinder you'll probably find that 3cfm rating is calculated with a usage factor of 25% or so.
wayne light
Haha, that scenario had crossed my mind. Tx!
No ‘not enough air’ issues at work for you!
You forgot, your compressor is rated 5.3scfm! Must not forget the S, very important. Without it they would be lying!
My desk fan can give you more CFM, no pressure
That's alot of sucking power for your tails Mr Heads.
@@nigelphuthi8861 Plenty of blow, no power
Considering mine uses a compressor and the Coanda Effect, yes. Mine does.
Was using a vaccume motor and impellor as a desk fan earlier (was only running at about 50v tho not the full 240)
Until you use a pressure optimised fan.
This awesome video is a great example of why we love AvE.
Plus, now we know why our air compressors that we paid good money for are usually disappointing pieces of shit.
when I worked offshore there was a compressor that could keep up with 4 sandblasting hoses at 120psi... but it was powered by a V12 Detroit pushing a V10 compressor and a 1500 gallon tank :)
ya, those guys sandblasting the rigs are def on continuous duty tools
Bunny Killer you was lucky , I worked land rigs we used putty knives and a needle chisel , but are air tank was a 2 stage Jims pump 5hp electric motor 100 gallon tank Diesel Electric Rig 2 Cat engines ran the light plant with two 640 volt generators. never run out out of air , unless a line froze -40
Other comment didn't post properly.
4.0 CFM * 90 PSI = 1171 Watts
Industry literature states 1/7 efficiency. Meaning 7 HP consumed by compressor to provide 1 HP at the tool.
1117 W * 7 = 8.2 killoWatts. US residential power is typically on 15 amp breakers.
120 Volts * 15 Amps = 1800 Watts.
8200 Watts / 1800 Watts = 4.5. Meaning we would need 4.5 times more power than we can get from a standard outlet in the US.
(1800 Watts * (1/7)) / 90 PSI = ~ 0.88 CFM. Meaning with 1/7 efficiency, this is about the most flow we can expect at the tool at 90 PSI. This is pretty close to what AvE found using Boyle's law and by measurement. Compressed air is notoriously inefficient in industry, and the significant financial incentive to fix that has only taken us thus far. Therefore, the only solutions are better power service and a storage tank to store energy while the tool isn't in use. The larger tank is the best solution for residential. In industry where that would be prohibitive and higher power is already brought on-site, a higher powered service is the solution.
We have 240 volt service also. Just wire in your own 240 volt outlet...
@@EETechs definitely a solution, but "regular" compressors are meant to work from existing outlets. And, most of them being portable, having a compressor that can work on almost any outlet at a jobsite is pretty useful.
EETechs higher power equals three hot wires
220 volts at 50hz makes a lot more sense than using air tools higher power density, so if you can use E only where you can't safely use air
@@shaunbarlow8993 Don't need three hots to get higher power, you can pull 12,000W on two hots.
The Word you were looking for is "Ansaugleistung".
Useless to know in a Compressor, useful to know for the young ones when looking for a better 3/4
@@DooMMasteR Woosh.
Bought a consumer 30 gallon and thought I could be happy.... Nope! Moved up to a 60 gallon commercial and was very happy but still not perfect...... Ended up getting a $3000 80 gallon and now I'm finally happy!
If that 30 gallon was labeled 4 cubic feet they might not have fooled you into thinking it would last more than half a minute before cycling.
Really delayed reply but also look at psi. I have an 80 gallon 150psi because higher psi squeezes more air into the same space as a 125psi compressor.
@@GroberWeisenstein most of those are only available with 3 phase motors and 3 phase isn’t common in many places.
@@GroberWeisenstein they have a lower CFM output than reciprocating compressors with the same HP though.
What about 'high cfm' rated hose couplings? is that B/S as well?
I suspected it's all BS but never could get to the facts. excellent work exposing this typical consumer fraud
It's worth taking a look at the "conservation of energy" aspect of this. The energy contained in a volume of compressed gas is basically equal to the pressure (above atmospheric) times the volume, in SI units it works out nicely. A flow of 4 CFM at 90 psi translates to about 0.002 m^3/s at 500000 N/m^2, multiplying that out gives a power of 1000 N•m/s (aka watts). Since compressors are more-or-less adiabatic, compressing air to 5 atm range will heat it up by around ~180 K, which means about 1700 watts lost to heat. So, unless the compressor is sucking 2700 watts out of the wall, it's not going to be supplying 4 CFM at 90 psi to the tool.
2k7W would require extremely efficient motor too, Likely it takes over 3kW to even start resembling any idea of reaching that volume at such high pressure.
@Indosarnia I used the adiabatic assumption just for a back-of-the-envelope estimate. I wouldn't trust the 1700 watts of heat to be spot-on, but perhaps to within ~±40%, which is about the level of uncertainty this whole calculation.
Before I joined the healthcare field, I worked for my father's equipment rental company. We had pretty large dual-piston, 2 stage compressor in the shop that we used for everything. Still, it could never keep up with large grinding or sanding jobs. I ended up plumbing our compressor through the wall of the building with a Chicago style air fitting on the exterior side. When I needed a constant supply of air, I would back our Sullair 185 towable diesel compressor up to the building and hook it into the shop compressor tank. Never ran out of air then!
Hot wet air
I’ve worked for Atlas Crapco for the last 8 years in Scotland as a tech. We are required to flow test our standard diesel driven compressors @24 bar. We usually output around 950cfm. (Just for some context) But the lower grade plug in ones are generally all the same no matter the brand.
The saddest part was when this broke your heart so bad you couldn't even finish the the usual finishing declaration.
Wow, that's actually pretty surprising... Those marketing fucks! Its like advertising a car has 300HP but there's 80% drivetrain loss, so its still slow as hell.
You mean exactly what they already do?
In an american car, they promise 300 HP, but don't mention that 200 of those horses run the fuel pump.
it actually makes more sense to rate a vehicle's hp at the flywheel. look at trucks for example , they come with multiple engine options in automatic , manual , 4wd and 2wd and every combination. transmission options would change the wheel hp , as well as adding in a transfer case. then they would have to supply you with the exact hp output for every combination. not to mention tire size. depending on the wheels you choose on a new car changes the tire size , and tire size would change the loss or gain of torque to the ground.
I feel like it's along the same lines as labeling something "military grade".
Yeah sorry bud, but this is exactly what they do... in this case though, everyone is using the exact metric, all the way up to multi million dollar hypercars, so you’re getting apples to apples. Also, there’s no specific task you’re trying to accomplish (unless we’re talking trucks) with this power besides move the car at a reasonable pace, which even 80hp cars accomplish, so, all good!
"Shocking!" -No one every
Thanks for verifying though. Another great AvE vidjeo. Edit: the scfm rating is really revealing.
I have watched a few of your videos so far and you sir are a genius and amazingly funny and informative! Thank you for taking the time to enlighten and amuse us at the same time!
Wow, have been wondering for quite some time how those ratings work.
Excellent video and thanks for taking the time to explain that for all of us out there!
AvE = Great IPM [InfoPerMinute] - many thanks
And in the canuckystan language, no doubt.
That's IPM going in, not out so...
When I was a wee lad, I really thought my shop-vac was 5HP because it said so on the sticker.
They get that number by measuring the suction power of the horse.
Brave engineers.
Best to go by the Ampere rating. Probably same is true with air compressors though I've never exactly checked the details.
@@johnpossum556 Not really--consumer-grade power tools are often rated by the "locked rotor" current consumption. Which is useless, because the tool isn't spinning.
Reminds me a bit of the old "EIA Music Power" ratings on audio amplifiers. Utterly meaningless for all practical porpoises.
But the keyword when buying a compressor mentioned in the video is "continuous duty" tool. Prosumer compressors are great for running nail guns and staplers, but those aren't continuous duty, unless you've got a very fast trigger finger.
@@tubastuff yeah because those tools only have one piston, not a rotary motor.
Amps have come a long way. Class D are dirtier than shit for THD but have lots of power in a small package with very little or no heatsink to speak of.
Admittedly I don't buy a lot of new tools anymore. I've been starting to favor going to pawn shops and buying an old tool I already like. Plus the benefits are if one dies I already have some parts for it.
@@2canines
Not hard to measure the suction power of a horse. All you need is a good vacuum gauge a pair of gloves and 2 bricks.
Love your vids, keep making them, never change your style!
Next up: How the household vacuum cleaner industry is bamboozling us.
But no really, they are...my vacuum sucks...and not in the good way
Go watch his videos on Dyson. Lol
Ahh, the math and the absolute pressure vs gauge pressure, etc. That makes sense. I learned in my fluid power (mostly hydraulics, but we covered pneumatic systems briefly) class that the compressors are rated at SCFM...at the inlet. That's where the standard is. The measurement is how much standardized air going in, not the capability to put air out at any particular rate or pressure. (and all the gas laws are, you know, add 14.7 (which varies with altitude/ambient air pressure) to your gauge pressures, then convert to an absolute zero temperature scale, and go from there..)
'Everyone' knows that you need a WAY bigger compressor than your tool(s) need in order to use them without running out of air in the reservoir (receiver), but why that is, total mystery. Nice to have that explained.
So the rated cfm is just the piston swept volume X rpm.
Hi, haven’t a clue where your background is from but I will just say that I have literally spent hours watching your awesome videos. You’re awesome fella. I am 54 years old,love mechanical engineering and so utterly messbrised by your way you explore and explain machines. I can’t thank you enough for your time and your help with us mortals. Don’t no your name and cannot seem to by a tee shirt but thank you. Jonny Taylor, North Yorkshire. Uk
My pleasure Jonhny. Thanks for joining me in the shop. Send your addy, size and style over to townpumpcnc@hotmail.com and I'll fling a tee your way.
“What the fuck kind of tool are you gonna run with that fart in a windstorm.”
Lose my shit at all your sayings; one of the most, if not the most, honest and funny guys out there. Always laughing and learning.
Love your channel.
Wow, that explains so much. Almost unbelievable, but that is how the marketing bs scams work! Thank you for that sweet explination!! Once again AvE 2020!!!!
SCFM = Stanley Cubric Feet per Minute. It's all science friction!
Thanks AvE! I nearly bought a consumer-grade compressor to use my air tools at the house... you just saved me future hours of frustration
Good work uncle ! You always teach me something and sometimes it’s not in a creepy way ! Keep up the great work !
We can estimate power needed to deliver 4 CFM at 90 PSI: P = 3,25 * 4 * 90 = 1,17 kW. (so we multiply cubic feet per minute by pressure drop in PSI and 'magic constant' 3,25 to convert it to watts). This is bare minimum if we assume 100% efficiency of compression (it all goes so smooth and slow that air doesn't heat up, so all the power goes only to build up pressure) and 100% efficiency of motor. For one-stage compressor it's obviously wrong, so we should at least double this value. So if compressor doesn't draw 2,4 kilowatts of angry pixies, no way it could deliver so much!
Isn't the compressor efficiency about 16%? Motors are about 98% so say 15% overall, so you need about 6x your calculation
S Koue Well in Europe, household outlets do 2.3kW as standard, 11kW at the big domestic sockets (3 x 16A x 230V), but that's maxing out the fuses.
Standard outlets are 16A, so between 3520 and 3840W depending on line voltage. It depends on what country you're in, some outlets in Sweden are only 5A or 10A, while in NL 16A is standard, and in the UK it's 32A. Which is why they have those retarded plugs with upto 13A fuses in them.
...on industrial grade machines the simplest method and will get you pretty close is about 4cfm per horsepower.....and at 575vac it's about 1hp per amp....also the base pressure is 100psi at a temperature range I don't remember lol.....now there are proper formulas to put you dead nuts on, but for the majority of applications the above 'formulas' work fine.
@@gcewing Don't you want the heat exchange from the tank to increase density? It's still the same amount of air in the bottle.
It's all about the actual CFM, drives me knuts, have to shop either used from the 60/70's or cut a load off to pay for it.
Best to find vintage and rebuild
Excellent analysis and uncovering of the marketing buggery.
Consumer reports should hire you yesterday! THANK YOU!!!
Don't think they could afford him at this point
I am a mechanical engineer, formerly the Engineering manager at Sandvik Mining equipment in Canada. We designed air compressors for ITH drilling. SCFM is the standard for rating compressed air. The "S" stands for stands for Standard. As I see it, the real travesty here is that your die grinder is rated in "non-standard" terms. Air volume is affected by temperature, humidity and pressure. All compressors (AND TOOLS) should be volumetrically rated by SCFM. For the record, Atlas Crapco does the same. Sorry dude.
No surprise here ... Snap-On publishes both CFM and SCFM data, as they should.
store.snapon.com/1-4-Collet-Die-Grinder-Air-Mini-Cushion-Grip-1-4-Collet-25-000-RPM--P650112.aspx
100 PSI. 1.7 CFM at 100 psi = 11 SCFM. For the most part, air is a linear spring.
1.7 x 100 = 11 x 14.7 (give or take)
Just for those that wanted to check, the specs AvE showed were 3.2 CFM, but 23 SCFM. Which is why it is sucking that compressor dry.
So @Scott Dalrymple If I understand correctly, a little math will get you from the advertised "bogus CFM" to a more helpful SCFM? Take the HF Earthquake XT 1/2in drive impact. It's rated 6.0cfm@90psi. So 6.0*90=X*14.7 give us roughly 36-37 SCFM.
If that is true, then you could simply take the CFM @Xpsi, multiply them and divide by 14.7 to know what sort of compressor you need. That would help a lot with the less honest tool manufacturers. But the truth is, that no 120v compressor is going to keep up with any tool, especially if they're under 15 amp. The advantage of an impact is that you would only need it for a few seconds at a time.
@@ScottDalrymple should 100psig be converted to 114.7 psi absolute to do that comparison?
@@shanewatson2491 Yes, you are right.
this is awesome would have never looked at the true flow
my mind is blown
You're opening comment was my grandmother's favorite saying she had it written on her refrigerator! Awesome! I can still hear her saying it in her High cackley voice and then laughing a big belly laugh Thanks for the Memories.
A bit long winded here. If you're into rigging, do this:
Start with your usual small compressor turned on by a wall switch as needed. Tee in all tanks you have, including used larger compressor you eventually acquire. Turn on larger compressor when doing the heavy stuff, taking a breather when your combined tanks run low. Also aim for trailer mounted backup, owned or rental, when needed. If you are the junk type, there always seems to be older compressors of many kinds discarded by others, available for the odd chore swap. Always enjoy more air, including launching anything through a quick release valve and a pipe, hundreds of feet away.
I just hear some slimy lawyer saying "Well technically..." in the distance with stuff like that.
i recently pre ordered a PC video game. im old school i like having the case and disc... when i finally got my hands on the case and opened it to put the disc in and install the game... what i found was a disc shaped piece of thick paper with the games serial number and instructions on where to download the game... i went and looked at the "marketeering" and sure enough is says game disc included... its a disc, it has the "game" access code on it. technically i got exactly what they said. but not what i expected. cavat emptor just dosent cut it anymore, the people making these things up know exactly how far they can take it.
@@painkillersclan Fallout 76 Collectors edition?
What hospital did you steal that airflow gauge from?
Or was it a nursing home?
I need to know because I need one....
Suggest you contact Dwyer Instruments. I use a lot of rotameters for work. Recommend the VF series.
www.dwyer-inst.com/Product/Flow/Flowmeters/VariableArea/SeriesVFC-VFCII#ordering
They are relatively pricey but they are worth their weight in gold.
Actually, CFM gauges like that are also used on regulators for MIG and TIG welders......
@@notajp woosh
@@notajp ... that was satire
Omega Engineering had good ones on the cheap
Love that you can call them out with hard numbers and facts!
I appreciate the explanation and the honesty. Keep up the good work.
Me, to my compressor:
"Can you maintain 90PSI? No pressure."
I have seen compressors that can keep up.
But they were designed to run all the air tools in a 150,000 sq ft factory floor.
and they cost your firstborn and a year of salary.
AvE mentions that at the end of the vid: industrial compressors are accurately rated--at the pointy end--where the air tool connects to the supply hose.
Those big twin screws with the 2,3 or 4" air pipe coming out, yeah baby.
AvE One of the best videos I've ever seen! I will have to keep this in mind when I shop for a compressor soon!
Great information. Thanks, I’ve always wondered what was going on with that.
Worth noting as well that most consumer compressors have duty cycles between 40 and 60 percent, so continuous use will let the smoke out of the motors in short order.
And that's per 10 minute cycle. I asked a salesman recently if their compressor would be okay with 30 minutes continuous use, they said no it's going to burn the motor up and that even 10 continuous is asking a lot, it was a $500 compressor. Seems you really need to jump to the >$1k level to get units that are made to keep up with tools like plasma cutters and die grinders.
Mat D yup. Try several $1ks
WOW, that explains a lot!! I thought that maybe the had a CFM / US like their gallons that they were workin with. Cheers, Billy in Ladysmith
Even some of the industrial compressor companies use skull duggary to sell their products. Thanks for bringing this out AVE!!! My company bought four top brand industrial compressors to the tune of almost $10K and the rated SCFM was still listed at double the actual tool use output. We sued and settle out of court and purchased another brand after actually testing the output under tool use before purchasing. We still lost money with all that additional legal tap dance and lost production but we are back in business now....
Total SCaFM !
Good job man, explaining this in simple term.
They just assume that all guys are using air compressors for is off dusting key boards.
Don't act like you don't use your rotary tool in pulses like the rest of us. 1 second on, 14 seconds to build up pressure, 1 second on...that's how they're supposed to run right?
@@PowerScissor exactly hahah
@@PowerScissor Would that be 4SPM? Four useable seconds per minute. :D
I used mine to save some intestines once.
I dont think any manufacturer has ever thought that.
The only compressor I had that I felt was delivering usable pressure for continuous duty with air tools was a Craftsman 20 gallon compressor powered by a 5 HP brigs and Stratton gas engine.
Every other compressor I had needed additional air storage, like a few of those small disposable Helium tanks in series (or parallel) piped into the system.
Good info was trying to use my air hammer at home today and had to keep stop and waiting on the air to build back up
I never did the tests or math, but you're spot on with this. I ended up hooking an extra 60 gallon tank to the 30 on my home gamer air compressor to help with air volume needs. But once you run that volume down and you're just on what the compressor is making, it can't keep up for crap.
Good stuff, don’t forget pressure drop in the air hose at those high flow rates, would be most accurate to measure air pressure at the tank instead of at the end of the hose.
the more hose,pipe you have the more voluum,like,?.vacuum,?,volume..
Wow the truth does hurt. The bank account that is. Thanks for the eye opening video buddy.
thank you for the eye opening information man, keep on doing the good work
First time I've heard you say "don't take no wooden nickels." Ole pops says that all the time to me.
I tip my hat to you good sir.
4 people are air compressor salesmen.
50 now! Hopefully this will go viral! lol
The solution, of course, is really big air storage tanks, and compressors running all the time.
AAAAAAH! Yes! Thanks for sharing!! This principle came to bear several years ago when working an a industrial project. >$250,000 was about to be spent on a compressor package. Per engineering principles and the combined gas law the ACFM (acutal cubic feet per minute) @ 100psi and 60F was estimated. Sometime during the initial bid the air compressor folks informed us that in the compressed air industry ACFM meant the cubic feet of air actually needed at the inlet of the compressor. Ended up rebidding the package after terms were better defined which yielded substantially more equipment and a higher price.
Hey mr AvE this is the best explanation the Internet has that I could find about the mystery about why my compressor can't keep up with anything. Wish I knew this sooner that they rate compressors at inlet pressure wtf
so if cfm is like amps and pressure is like volts it makes an enormous difference. It's like saying it delivers 90 amps at 1mV.
Bought a kobalt air compressor from lowes and it said tool ratings are often 25% of what should be expected. That lines up with what you are seeing. Want a picture?
He's seeing 1/10 the expected performance, how does that line up?
Or are you talking about the useless 3.5 CFM @ 0psi? That's the least important part of the problem.
25% sounds like the ditt cycle, so worst case multiply by four to get to 100%.. and then multiply again by 6 to go from scfm at 0psi to 90psi. Or IF you use bar, multiply by 6 to go from 0bar to.. 6bar!
You gotta run it in a vacuum at 0 g during the transit of Venus to correct rating.
Dont give them ideas
I always wondered why my 13.6 cfm ingersoll can't keep full power on air tool.thanks for the enlightenment
THANK YOU FOR THAT EXPLAINATION!!! I have been so frustrated for so many years wondering why MY compressors could never keep up with MY tools. Now I understand it’s completely impossible because the scumbags are lying to us.
Awesome. So I guess the solution is to Daisy chain multiple 60 gallon compressors or something, unless you have access to genuine industry air compressors? ...My wallet just shrieked in horror and ran away. I'm a little freaked out.
Lol, AVE, you rock. Best wishes for your health and happiness!
this is exactly what I do when using an air arc. string 4 of those little turd boxes together and they can start to flow some air.
Do you mean parallel them up?
Daisy chain sounds like feeding the first compressor output into the inlet of the next one.
It wouldn't improve your flow rate but the mushroom cloud might make an interesting spectacle for your neighbors. :-)
Yes this, T two together. I do the same thing with the $110 ones with the two wheels on the back and handle in front. I was able to paint for a 4-5 minutes continuously before they had to catch up, wish I could remember the spray gun cfm @90 rating. You get way more cfm per dollar this way and can plug into different breakers.
6.0 cfm at 30psi (thank you amazon orders from 2015)
@@alangunn7254 I was more visualizing a "chain" of fittings, tees, and so on, connecting all the outputs of the compressors to a single air line... Yeah, I guess it is a bit like wiring in parallel, isn't it. Still, I like "Daisy chain" It's like sticking a flower in a pile of shite: it's still shite, but now it's got a daisy in it!
I like my frankensteined fridge compressor . Cant wait for it to go boom.
Wow... Well done on the calculus. Something to look for is FAD free air delivered.... this gives you a better idea. Also something all hooby users need to be aware is on a lot of compressors the motor may be rated at 80/90 % duty time meaning the motor cannot run continuously !!. Keep it up. Well done . Regards Don.
Good eye-opening talk. I was always wondering why my "big" compressor could NOT keep up with my turbine (dental tool),
Let alone those commercial small ones they sell to veterinary dentists as tools. Thanks.
Most ads/specifications rate the compressors a so many SCPM. The "S" says that you measure the volume of air at "standard" conditions of one atmosphere.
Almost as bad as the ratings is the noise produced by the home gamer compressors, especially the oil free compressors.
I’m stuck with an oil-free 30 gal POS I bought at HFT. Never again.
So happy to get back from vacation to find some warning signs in the mail. Thanks Ave!
Thank you for such a clear and complete explanation.
A friend of mine and I each bought the same model air compressor four years ago. His began to malfunction and eventually stopped 16 months in. Mine has yet to give me problems but I did do the break in procedure the first time I used it. This involved running the compressor for 30 minutes non stop with the drain open. My question is do you think this procedure would affect the cfm output? Also did the battery powered compressor call for a break in?
Great content! Keep up the good work.
Not really. It is mostly to match the piston and cilinder together.
You could lose a bit of compression but nothing like this.
It is mostly for longevity because of wear.
Now you need to check the actual flow rates of the tools. I would be interested in seeing if they are using the same standard in rating them.
I believe his first test did show that the die grinder was using around the same CFM as its rated for while running. At 3:43 the gauge reads 3.5ish at full chooch from the die grinder at 100-110 PSI.
It makes sense for the tool to use the inlet pressure for its rating - that's the pressure you need to deliver for the tool to work at maximum capacity. There is literally no reason for them to lie about that number.
It does not make sense for a compressor to be rated on the inlet pressure, because that is not what you need to do work. You need outlet pressure, so you can match it up correctly with the tools.
What's worse is someone who works with industrial air compressors is even more likely to be filled by the false advertising, because industrial tools are rated on the outlet pressure like they should be. They can get away with such dirtbag tactics that the consumer grade stuff can.
Makes sense after you explained it. We have a 60 gallon 230v air compressor in the shop, and it's about 12 years old. I believe it says it does 11CFM on the sticker. It's nothing expensive but does what we need and use it for. If we use some of the larger air tools, you can for sure drain it. Heck, just filling up some of the larger tractor tires can drain the tank and make it work and yet some of these semi portable or standup portable units say they'll do half the CFM or close to it with tiny tanks and pistons? What? Yah, now that you explained it and showed the BS it's clear now what's going on.
On a side note, there's deceptive practices similar to this in the automotive world regarding turbo and super chargers. Gale Banks does some great informative work in breaking down the BS and showing what the numbers really mean and what numbers really matter.
Stuck here in Brexit-zuela, I remember a friend worked with compressors and he said in UK they were rated in cfm "FAD" (Free Air Delivered), so for an air tool using air at 90psi, you need 6 times the cfm rating for the compressor.
I ended up with 3 cheap 240V "8 cfm" compressors linked together and I draw air directly from one of the tank end plugs. Together they can just about run a die grinder without resting and they really heat up my man-cave. Crazy!
Thanks for the explanation AVE; makes so much more sense now! Well, the problem - not the wankery.
Designer "Our compressor will run ANY tool!......(*for five seconds with no load)"
Marketing "Sounds good but lets all leave out the second part OK?"
CEO "And multiply the rating by five."
All manufacturers "So we agree, let's meet here again if they figure it out."
*All scurry away into the dark corners of the alley...
As someone starting to dabble in the home game, this was helpful hell. Hats off to you.
You are the best real world Physics teacher I have ever had. Schookum
Thats why we need a 15cfm compressor to run a 5cfm sander
We have a quad of VFD drove Sullairs, 1200CFM @ 120PSI, does that follow the concept of "the highest rated compressor can virtually never keep up with the lowest rated tool"? If needed for a die grinder they build them much bigger than those, MORE POWAH!
Wow, what do you do that requires that much air?! :o
@@SuprSi a whole plant full of automated automotive spot welding cells for instance. Almost everything pneumatic powered. Just an example from what I did for a while.
1.200cfm each?....sounds about like 300hp each...or 4 75hp VSD machines... medium to smaller machines...least from I'm used to lol....work on everything from 5hp all the way up to 500hp rotary screw machines....oil flooded and oil free..
I used to work on an offshore drill ship. We had 4 IR scroll compressors rated at 900 CFM each, and we'd routinely have all 4 running at 100% load and still not be able to maintain system pressure. Blew my mind. So like he said, no matter what you have, it still isnt enough sometimes.
@@angusandleighYep, 300hp each, dual stage flooded screw, the VFD can go as low as 450cfm before the motor risks stalling and the unloader opens up.
I can recommend getting a three phase compressor and overclocking it with a vfd. Very fun to do and helps with power.
I mean i got the bell on, i dont get notified of your videos anymore, this is a cause for concern, your worth watching
I literally finished watching this on patreon about 5 minutes ago
Ah! Hmm. Will never buy another air tool, ever. Wish I knew this before I invested heavily in air tools. So pissed
Thanks for explaining. It's hard work using a plasma cutter being fed by 2 compressors one from Aldi the other from Lidl.