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?
In the U.K. the size of a compressor is stated as either Swept Volume or Free Air Delivery. Swept vol. refers to the actual displacement of the pump. Free Air Delivery is what you get. There are some disreputable suppliers in the UK that will only give swept vol and when asked about FAD won't give a value.
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.
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
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.
@@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.
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.
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
Another thing about the cheaper air compressors. They print the exaggerated horsepower on the tank, and the big 5 hp on the tank is not to be seen on the undersized motor. The motor will generally have SPL, in the hp spot, so you have to judge by the amps and voltage in order to estimate the horsepower. I had a Sears 3 hp that had a 1.5 hp motor, and the next one was called a 5 hp, but the motor was 3 hp, and finally I bought a Quincy with a big 5 hp motor, with a pump that weighed more than the previous Craftsman air compressor all together.
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.
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.
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!
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.
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.
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 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
@ 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
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.
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.
@@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.
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.
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 :)
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
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.
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.
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.
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!
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!
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
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.
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.
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!
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.
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!!!!
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.
@@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.
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....
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.
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.
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.
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
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.
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!
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.
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.
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?
How close are they without the hose though? I just recently ran into the issue at work where I had 130 psi at the wall for a tool that required 90, but having 100ft of 3/8" hose meant that I was only getting 60 psi at the tool. The solution in the end was to step up to 1/2" hose instead of the usual 3/8", and 3/8" fittings instead of the usual 1/4". Either way a lot of people don't recognize that hoses cause a TON of loss. I'd be willing to bet that the output at the compressor with no hose is a lot closer to what they're advertising. Its still probably not all the way there, but I'd bet its a lot closer.
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!
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!
Back in the day working in a machine shop, we got an Ingersoll Rand screw compressor that put out 63 CFM @ 125 psi and we used a 200 gallon tank with air dryer and ran 2” cast iron line that went around the shop in a loop with drops at every machine. Started off with (2) 80 gal freestanding compressors but they couldn’t keep up with the machines and they got so hot there was always water in the line!
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.
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.
I always figured the discrepancy was in a duty cycle calculation, like 4cfm at 90psi if you only use the tool 20 seconds of every minute (welders is a big one that comes to mind). Now I'm sitting here wondering why they don't use a duty cycle calculation as they could provide a graph with the pressures/cfm it can produce at varried duty cycles and it would be really easy to find the one that's right for your garage.
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.
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!
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.
@@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!
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.
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
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.
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.
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!
@@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.
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.
Change your hose size and remove as many QD's, filters, and any other line restrictions. You will see different results. However, you can only validate the compressor performance for rated flow and pressure at the STP (Standard Temperature and Pressure) used by the manufacturer. STP is a measurement standard to make sure everything is compared apples to apples. You have to adjust the compressor rating and tool rating for YOUR test conditions (altitude [pressure], temperature, and humidity) and you have to account for line friction. The short version is that as altitude, humidity, and temperature go up; the compressor flow capacity goes down and the tool flow demand goes up. The performance WILL change continously depending on those variables listed above. For my location in Eastern Idaho, there is a 15% loss due to altitude alone. July max temperatures reduces that capacity another 8%. This is true of ALL compressed air systems. The compressors I manage at work are manufacturer rated for 905scfm@125psi. What I actually get is anywhere between 705 and 770cfm depending on the ambient air temps. These compressors are performing EXACTLY as designed. The reality is the same compressed air system will perform differently in July than it will in January. It will perform differently in Denver than it will in Orlando. Why does humidity matter you might ask, because when you compress air to 100psi, a large portion of the "gas" you compressed is water and it condenses out to rust your tank (assuming you don't drain it regularly). It is, for practical purposes, a normal expected power leak. The only way to eliminate that power leak is to live where there is 0% humidity. Compressors are usually rated at 0% humidity. The problem with STP is there isn't only one universally agreed upon STP. There are many different standards, depending on the industry. ISO STP was 14.7psi before 1982 and 14.5psi after 1982. ISO uses 32degrees F. NIST uses 14.7psi and 68 degrees F, but calls it Normal temperature and pressure (NTP) and uses it for chemistry experiments. NIST also uses 60 degrees and 14.5psi for thermodynamics experiments. Most use 0% humidity, but some don't. SCFM (Standard Cubic Foot/Minute) is defined as some total number of molecules in a given volume at a specific temperature and pressure. SCFM or FAD (free air flow delivery) are the same thing, just with different units. The problem is air doesn't have a fixed density. It is dependent on pressure, temperature, and composition; so it can't have a fixed definition of molecules per given volume. In electrical terms SCFM is the comparable to Amps and Pressure is comparable to Voltage. It’s not a direct comparison, but close enough. Fortunately, Amps do have a single universally defined quantity. One amp is equal to one coulomb or 6.24x10e18 electrons worth of charge moving past a point in a second. Just like you can't get 100amps at 120 volts through a 28ga wire, you can't get 100scfm through a 1/4" hose at 100psi. Coming from a compressed air engineer, line friction is one of the biggest misunderstandings in any compressed air system. It doesn't matter whether you have a party balloon or the Goodyear Blimp worth of air behind it, there is only some much you can push through a soda straw. So the compressor manufacturer ratings are not lies or intentionally misleading, but they are often misunderstood and incomplete. The proper way to write an air compressor rating is 15 SCFM@100psi for ISO STP. If your test conditions don't match ISO STP and 100psi, it will be impossible to measure the same flow rate as the factory rating. IE: You will not be comparing apples to apples. Also, the tool ratings are more likely the misleading rating. All air tools have a duty cycle rating, not a continuous flow rating. What this means, for example, if a tool has flow rating at 5cfm and a duty cycle of 30%, the 5cfm rating is the average of 15cfm for 20 seconds and 0 cfm for 40 seconds. Duty cycles often aren't published and are often overlooked when they are. Impact werenches are notoriously misleading because of this duty cycle idea. Your standard box store air hoses--50ft long 1/4" and 3/8" often can't flow enough air for 15cfm and maintain 90psi at the end of the hose. Just like wire sizes and electricity, air hose performance is dependent on length and the desired load. At 15cfm, 1/4" hose has roughly 1psi loss/ft of length, and 3/8" is has about 0.1psi/ft. This does not include any losses from QD's, filters, check valves, water separators, etc. By the way, while your math generally correct, your interpretation of CFM at the intake vs CFM at the output is wrong. A Standard CFM at 14.7psi has the same quantity of molecules as a Standard CFM at 100psi. It has just been compressed into a smaller volume. There is a difference between SCFM, ACFM, and ICFM. They each vary based on actual air density.
Hey AvE! I got your next project! Make/or buy an adapter to hook up multiple air compressor to some inlets to one outlet for a tool! I would be interested in seeing how many air compressors it would take to maintain a constant PSI when a tool is in use. I’m thinking about 3-4, but I could be wrong.
Simply put, there is less air in a cubic foot of 14psi air than there is in 90psi air. The tools are rated with 90psi air volume, and the compressors with the ambient pressure air.
I have found the same issue with my compressors and I have decided on a gas powered unit cobbled together from scrapped compressors. I have also added tanks much like your air pig beside your compressor. I need more than 30 seconds of flow at 60 psi for my plasma cutter. Things get messy when their isn't enough airflow. I have having to stop and wait for the compressor to recover.
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...
Nice video though admittedly I knew they were doing this before watching. My question is: What quiet small oil free compressors are out there that can actually deliver a decent true cfm of around 4 @ 90psi? Are there any good brand names were don't have to second guess what a true output CFM rating is? I need something small that can handle 4.2cfm @ 40psi. It has to be small, and quiet. And not cost an arm and a leg. I'm having a heck of a time trying to find one.
Yeah noticed this when i bought my first proper continuous cycle air tool and tried to use it in work. Even my twin cylinder (consumer grade) is struggling to produce enough air for it. Hence if anything bigger needs to be done, i daisy chain two compressors to DIY extra capacity air tank. With this setup it can be used normally. Thankfully both compressors were pretty much free for me and i get plenty of those since people dont know how to repair them, chuck into metal bin and from there i get to save them.
I have the same compressor and use a large air storage tank to buffer the shortcoming of the constant output of the compressor when using a HVLP sprayer or air nozzle tool.
I worked in a tool store as a teenager and always new the CFM ratings were BS but never knew how the ratings were determined until now, thank you . I remember the boxes for Ingersoll Rand tools use to give two drastically different air consumption ratings, this rating method might be why. Also I did not follow why you added 14 psi to P2 when using Boyle's law, did I miss something? Awesome video, your setup to show the the actual flow rates was great.
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?
@@timmarrier wtf are you going to do with a tool that can run continuously, but only at no load?
In the U.K. the size of a compressor is stated as either Swept Volume or Free Air Delivery. Swept vol. refers to the actual displacement of the pump. Free Air Delivery is what you get. There are some disreputable suppliers in the UK that will only give swept vol and when asked about FAD won't give a value.
Perfect lol😂
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.
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.
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
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 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...
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.
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
Another thing about the cheaper air compressors.
They print the exaggerated horsepower on the tank, and the big 5 hp on the tank is not to be seen on the undersized motor.
The motor will generally have SPL, in the hp spot, so you have to judge by the amps and voltage in order to estimate the horsepower.
I had a Sears 3 hp that had a 1.5 hp motor, and the next one was called a 5 hp, but the motor was 3 hp, and finally I bought a Quincy with a big 5 hp motor, with a pump that weighed more than the previous Craftsman air compressor all together.
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've learned more from this channel than I did in all of high school
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?
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.
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
@ 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
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.
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.
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.
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.
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
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.
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.
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!
I suspected it's all BS but never could get to the facts. excellent work exposing this typical consumer fraud
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
So the rated cfm is just the piston swept volume X rpm.
AvE = Great IPM [InfoPerMinute] - many thanks
And in the canuckystan language, no doubt.
That's IPM going in, not out so...
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
"Shocking!" -No one every
Thanks for verifying though. Another great AvE vidjeo. Edit: the scfm rating is really revealing.
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.
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.
this is awesome would have never looked at the true flow
my mind is blown
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..
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.
The saddest part was when this broke your heart so bad you couldn't even finish the the usual finishing declaration.
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!!!!
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.
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.
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....
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.
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.
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
SCFM = Stanley Cubric Feet per Minute. It's all science friction!
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.
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
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 the truth does hurt. The bank account that is. Thanks for the eye opening video buddy.
I always wondered why my 13.6 cfm ingersoll can't keep full power on air tool.thanks for the enlightenment
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
Consumer reports should hire you yesterday! THANK YOU!!!
Don't think they could afford him at this point
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.
Love that you can call them out with hard numbers and facts!
Love your vids, keep making them, never change your style!
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.
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.
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
How close are they without the hose though? I just recently ran into the issue at work where I had 130 psi at the wall for a tool that required 90, but having 100ft of 3/8" hose meant that I was only getting 60 psi at the tool. The solution in the end was to step up to 1/2" hose instead of the usual 3/8", and 3/8" fittings instead of the usual 1/4". Either way a lot of people don't recognize that hoses cause a TON of loss. I'd be willing to bet that the output at the compressor with no hose is a lot closer to what they're advertising. Its still probably not all the way there, but I'd bet its a lot closer.
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.
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!
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!
Back in the day working in a machine shop, we got an Ingersoll Rand screw compressor that put out 63 CFM @ 125 psi and we used a 200 gallon tank with air dryer and ran 2” cast iron line that went around the shop in a loop with drops at every machine. Started off with (2) 80 gal freestanding compressors but they couldn’t keep up with the machines and they got so hot there was always water in the line!
Total SCaFM !
Good job man, explaining this in simple term.
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.
Me, to my compressor:
"Can you maintain 90PSI? No pressure."
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.
I like my frankensteined fridge compressor . Cant wait for it to go boom.
I always figured the discrepancy was in a duty cycle calculation, like 4cfm at 90psi if you only use the tool 20 seconds of every minute (welders is a big one that comes to mind).
Now I'm sitting here wondering why they don't use a duty cycle calculation as they could provide a graph with the pressures/cfm it can produce at varried duty cycles and it would be really easy to find the one that's right for your garage.
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.
Good work uncle ! You always teach me something and sometimes it’s not in a creepy way ! Keep up the great work !
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!
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.
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.
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.
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.
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 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?
Change your hose size and remove as many QD's, filters, and any other line restrictions. You will see different results. However, you can only validate the compressor performance for rated flow and pressure at the STP (Standard Temperature and Pressure) used by the manufacturer. STP is a measurement standard to make sure everything is compared apples to apples. You have to adjust the compressor rating and tool rating for YOUR test conditions (altitude [pressure], temperature, and humidity) and you have to account for line friction. The short version is that as altitude, humidity, and temperature go up; the compressor flow capacity goes down and the tool flow demand goes up. The performance WILL change continously depending on those variables listed above. For my location in Eastern Idaho, there is a 15% loss due to altitude alone. July max temperatures reduces that capacity another 8%. This is true of ALL compressed air systems. The compressors I manage at work are manufacturer rated for 905scfm@125psi. What I actually get is anywhere between 705 and 770cfm depending on the ambient air temps. These compressors are performing EXACTLY as designed. The reality is the same compressed air system will perform differently in July than it will in January. It will perform differently in Denver than it will in Orlando.
Why does humidity matter you might ask, because when you compress air to 100psi, a large portion of the "gas" you compressed is water and it condenses out to rust your tank (assuming you don't drain it regularly). It is, for practical purposes, a normal expected power leak. The only way to eliminate that power leak is to live where there is 0% humidity. Compressors are usually rated at 0% humidity.
The problem with STP is there isn't only one universally agreed upon STP. There are many different standards, depending on the industry. ISO STP was 14.7psi before 1982 and 14.5psi after 1982. ISO uses 32degrees F. NIST uses 14.7psi and 68 degrees F, but calls it Normal temperature and pressure (NTP) and uses it for chemistry experiments. NIST also uses 60 degrees and 14.5psi for thermodynamics experiments. Most use 0% humidity, but some don't. SCFM (Standard Cubic Foot/Minute) is defined as some total number of molecules in a given volume at a specific temperature and pressure. SCFM or FAD (free air flow delivery) are the same thing, just with different units. The problem is air doesn't have a fixed density. It is dependent on pressure, temperature, and composition; so it can't have a fixed definition of molecules per given volume. In electrical terms SCFM is the comparable to Amps and Pressure is comparable to Voltage. It’s not a direct comparison, but close enough. Fortunately, Amps do have a single universally defined quantity. One amp is equal to one coulomb or 6.24x10e18 electrons worth of charge moving past a point in a second. Just like you can't get 100amps at 120 volts through a 28ga wire, you can't get 100scfm through a 1/4" hose at 100psi. Coming from a compressed air engineer, line friction is one of the biggest misunderstandings in any compressed air system. It doesn't matter whether you have a party balloon or the Goodyear Blimp worth of air behind it, there is only some much you can push through a soda straw. So the compressor manufacturer ratings are not lies or intentionally misleading, but they are often misunderstood and incomplete. The proper way to write an air compressor rating is 15 SCFM@100psi for ISO STP. If your test conditions don't match ISO STP and 100psi, it will be impossible to measure the same flow rate as the factory rating. IE: You will not be comparing apples to apples.
Also, the tool ratings are more likely the misleading rating. All air tools have a duty cycle rating, not a continuous flow rating. What this means, for example, if a tool has flow rating at 5cfm and a duty cycle of 30%, the 5cfm rating is the average of 15cfm for 20 seconds and 0 cfm for 40 seconds. Duty cycles often aren't published and are often overlooked when they are. Impact werenches are notoriously misleading because of this duty cycle idea.
Your standard box store air hoses--50ft long 1/4" and 3/8" often can't flow enough air for 15cfm and maintain 90psi at the end of the hose. Just like wire sizes and electricity, air hose performance is dependent on length and the desired load. At 15cfm, 1/4" hose has roughly 1psi loss/ft of length, and 3/8" is has about 0.1psi/ft. This does not include any losses from QD's, filters, check valves, water separators, etc.
By the way, while your math generally correct, your interpretation of CFM at the intake vs CFM at the output is wrong. A Standard CFM at 14.7psi has the same quantity of molecules as a Standard CFM at 100psi. It has just been compressed into a smaller volume. There is a difference between SCFM, ACFM, and ICFM. They each vary based on actual air density.
so a 13hp gas 27cfm campbell hausfeld compressor is on the cutting edge of usability
I can recommend getting a three phase compressor and overclocking it with a vfd. Very fun to do and helps with power.
The CFM bit is at 7:00. I do enjoy the verbal chowder but sometimes I want to get to the point :).
BEEP BEEP READ THE DESCRIPTION WEE WOO WEE WOO
Hey AvE! I got your next project! Make/or buy an adapter to hook up multiple air compressor to some inlets to one outlet for a tool!
I would be interested in seeing how many air compressors it would take to maintain a constant PSI when a tool is in use. I’m thinking about 3-4, but I could be wrong.
The solution, of course, is really big air storage tanks, and compressors running all the time.
You are the best real world Physics teacher I have ever had. Schookum
Simply put, there is less air in a cubic foot of 14psi air than there is in 90psi air. The tools are rated with 90psi air volume, and the compressors with the ambient pressure air.
Uh..
@@RobertSzasz oops, got my words mixed up.
yeah it can supply the cfm and the psi, but not at the same time hahaha. they dont tell you that tho
Not quite. But the comoressor he shows says @90psi.
I have found the same issue with my compressors and I have decided on a gas powered unit cobbled together from scrapped compressors. I have also added tanks much like your air pig beside your compressor. I need more than 30 seconds of flow at 60 psi for my plasma cutter. Things get messy when their isn't enough airflow. I have having to stop and wait for the compressor to recover.
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...
Thanks! I had no idea why my big ass comp, can't run my paint gun when the numbers work :( I have to pace myself to get it done.
Thanks for the explanation AVE; makes so much more sense now! Well, the problem - not the wankery.
Nice video though admittedly I knew they were doing this before watching.
My question is: What quiet small oil free compressors are out there that can actually deliver a decent true cfm of around 4 @ 90psi?
Are there any good brand names were don't have to second guess what a true output CFM rating is?
I need something small that can handle 4.2cfm @ 40psi.
It has to be small, and quiet. And not cost an arm and a leg.
I'm having a heck of a time trying to find one.
Didn't the audiophile companies get caught in a similar scam in the 1970s with amp power ratings?
Peak Music Power!
en.wikipedia.org/wiki/Audio_power#PMPO
More than twice the wattage than you are actually getting!
As in Watt the F???
Yeah noticed this when i bought my first proper continuous cycle air tool and tried to use it in work. Even my twin cylinder (consumer grade) is struggling to produce enough air for it. Hence if anything bigger needs to be done, i daisy chain two compressors to DIY extra capacity air tank. With this setup it can be used normally. Thankfully both compressors were pretty much free for me and i get plenty of those since people dont know how to repair them, chuck into metal bin and from there i get to save them.
I'm just going to times the CFM of the tool by 5. I don't have enough fingers and toes for division.
if you need this division thing just multiply the compressor output by .2 which is divide by 5
@@joejane9977 My fingers don't do decimal points either.
I have the same compressor and use a large air storage tank to buffer the shortcoming of the constant output of the compressor when using a HVLP sprayer or air nozzle tool.
Thats why we need a 15cfm compressor to run a 5cfm sander
I worked in a tool store as a teenager and always new the CFM ratings were BS but never knew how the ratings were determined until now, thank you . I remember the boxes for Ingersoll Rand tools use to give two drastically different air consumption ratings, this rating method might be why. Also I did not follow why you added 14 psi to P2 when using Boyle's law, did I miss something? Awesome video, your setup to show the the actual flow rates was great.
Ah! Hmm. Will never buy another air tool, ever. Wish I knew this before I invested heavily in air tools. So pissed
Gauge says " flow at stp" if it's in the line it's not at stp so you can't trust the reading, measure the flow at the output of the grinder
Seems like we need a standardized 3rd party rating system to keep the tool makers honest.
there's a glosaary of ave terms so if I'm not mistaken skookum already has a standard meaning
Kinda like the usda and meat... except that its corrupt AF
Good job. Never thought about that, but it all makes sense now, why my chinesium compressor is rated at a bazilion of cfm (l/min in my land).