How gas pumps know when to turn themselves off
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Gas or petrol pump nozzles turn off automatically when your tank is full. The way it works is really clever and uses the venturi effect.
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If I've set things up right, the title of this video should say "gas" for US people, and "petrol" for UK people! If you're in one of those countries, can you confirm?
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how did you do that? im in us and it says gas
It says petrol in the UK
American here, it does show as “gas”
Thats really cool!
Gas for America
Petrol in uk. 🎉
You can feel the petrol (water) hammer/hydraulic shock when the pump shuts off as the valve closes as well. Always wondered about that, cheers Steve this was really interesting
Oh yeah! Good observation
Yea, and see the whole hose jump from that effect.
@@SteveMould From your demonstration, it also seems like when the gas valve gets closed, the fluid flow is now pushing the valve shut (it was held open by the lever action), which probably contributes to it slamming shut. Which I presume is also good at ensuring that the gas flow stops immediately.
I bet if you had made your plastic cutaway demonstrator with a much larger diaphragm, it would have moved a lot further. Since there's no such thing as negative pressure as you said, the diaphragm moves because outside air pressure pushes on it since there is lower pressure pushing back on the other side. That's how the power brakes in a car work - they aren't being actively pressurized (except maybe when your ABS gets triggered), and instead a vacuum from the intake manifold of your car engine is formed on one side of diaphragm that can be up to 11" wide. That's 95 square inches, for a maximum sea level force of 1,425 pounds, and that is multiplied through the master cylinder like with the pedal leverage. Thus even a partial vacuum in your power brake booster has force comparable to how much you can press down on the brake pedal with all your might.
What is the mechanism that triggers the shut off when flow is stopped at the pump? I cannot see it clearly.
@@iAgos46 It could be a simple pressure sensor somewhere in the whole tube system. It also depends on the pump used - it can be simply running all the time you take the nozzle assembly out of the main body till you return it - some pumps have no problem to pump the liquid against the closed system - in that case you need no sensor just the one that checks if the nozzle assembly was returned back
I am fascinated by how much simple technologies are put together inside that thing and how hard it is to explain how they interfere with each other…
Cause theoretically they’re not simple, the fluid mechanics behind them is quite fascinating
you would enjoy this th-cam.com/video/gwf5mAlI7Ug/w-d-xo.html
Interact*
Some people can explain in 2 minutes what others take 2 hours to do.
Well, it is multiple simple devices put together to make a somewhat complex device.
I’m a an engineer and I used to work for the company that originally created that design. Actually, I redesigned that ball bearing mechanism. I can confirm that you are correct in your assessment of how it works. Also, most gas nozzles have a second diaphragm or plunger (not membrane) that deflects when there is pressure in the fuel line. It is used for prepay fill up. When you hit the prepay amount the dispenser shuts off, the pressure in the nozzle drops and that second diaphragm which is spring biased up will move and shut the nozzle off. There is a third shutoff in some nozzles that is called an attitude device. When a … moron… pulls a flowing nozzle out of a car’s fill pipe, a ball bearing blocks the pickup tube and shuts the nozzle off.
Please make a video about that too :P It's quite difficult to understand how prepay is hit and what happens when a moron pulls out a flowing nozzle out of the car.
Cool story Mr "I am an Engineer"
I'm the bearing and I can confirm this is a lie
Anti-moron mechanism lol
Regarding the attitude device, what if I want to fill up a spare container of gasoline or something like that? Wouldn't the 'attitude' device prevent me from doing so?
I had it, then lost it. Had it, lost it again. Then I got it. I love how you keep explaining with different visual examples. Such a great teacher.
This is one invention that never seems to fail. It's never failed for me and I'm 66 years old. I've never seen or heard of this valve not working from other people either. That's quite a successful bit of engineering, I'd say.
Physics works.
I've found (accidentally) that it is possible to make the valve fail, at least on some pumps, if you are only partially pulling the trigger (so that the flow is reduced). Specifically, I was watching the meter (instead of the nozzle), trying to put in a "round number" amount of fuel, without realizing that it was just slowly overflowing onto the ground!
I'd guess that the reduced flow-rate also reduces the "negative" pressure on the diaphragm, such that it can't overcome the spring force (to then shut off the fuel).
Oh it fails. Never fully trust it
I agree, Robert. It's a very clever bit of engineering going into those things.
Lucky you. It faild 4 times on me till now and I'm only 33. One time spilling all the gas and Three times stopping multiple times bevor the tank was full.
I remember looking up how this worked a few years back. The fluid dynamics and drawings went way over my head and I was left confused. Incredibly impressed (but not surprised) that you managed to clearly explain the mechanism to a total lay person in just over ten minutes!
I've been going through an engineering course over the last couple years, and I've learned a ton about fluid physics and dynamics. This video covered so much of those classes all at once and explained it all so clearly and succinctly, such in-depth topics so concisely, he makes it look easy! This video is incredibly well done!
I read a youtube comment about it a couple days ago and didnt really understand it. The visual explanations really helped it click all together!
@@micahphilson because "highly" educated people think to complex, i follow a professor here on tube, it's pretty much theory, but no practical experience and rather clumpy.
they have a star mind, not really open for new things and ideas, than someone without a university degree comes along and leaves the professor stunned and in the dust.
you shouldn't really admire these people, they aren't really smart al better at numbers because of routine. they can't solve simple things.
@@AnalogDude_ I'm in a military training program, we're only learning about the systems and the theory behind the systems we use, and working practically with those systems. We're taught by people with like at least 6+ years of experience, not professors.
But to do it, we have to learn all the theory and physics, chemistry, materials science, fluid dynamics, engineering etc. behind it all because it's literally nuclear physics and nuclear power.
@@micahphilson waste of time, people that see ghost where there aren't, better the invent something on your own and hope that it sells. they asked me as well when i was 18 and i told them you must be joking, you must be out of your mind and they left me alone, recently i got to speak to one of these people, lol.
My parents ran a gas station and I helped them since I was a child. Your explaination helped me understand a phenomenon I experienced many times in my first twenty years of life! Very ingenious, hope someone was rewarded for this mechanism. Nice video and very good explaination, thanks!
someone was rewarded... by a paycheck... so dont worry!
Taking the time to create the demonstration models really helped to nail this! Your delivery was pitched just right without resorting to dumbing down the content. Thank you!
As a (retired) technology teacher, I can respect the huge investment in time and energy needed to make and test those models. Also your perspex models are getting better as you learn. Good jobs all round.
Like what Edward R. Murrow said about television except put in the hands of people who care about such things- "This instrument can teach, it can illuminate; yes, and even it can inspire. But it can do so only to the extent that humans are determined to use it to those ends."
you must have been amazing teacher
@@AdiAgeraRS i get the same energy
And the money he makes on youtube.
It's amazing how clever the guys were who invented these things. Wonder when a woman will ever invent something like this
I was mentored by the two engineers who patented this back in 1965 and worked with them for over three years. They are both gone now, but they gave me a lot of knowledge during that time. One was like a second father to me and he was as detailed and meticulous as one could be. They two men didn't get much out it as like most corporations do, the board takes it all for themselves.
fascinating to find those with near 0-degree connections to things like this. Have you any stories from the 2 engineers you're keen to share?
Why not mention their names?
@@JoaoGauss that's because the world is far more complicated than just having a really good idea. Marketing, logistics, accounting, managerial skills are all critical to turning a good idea into a gold standard. I'm not saying we can't make improvements, but the skills to take a product to market are just as important as having the idea for the product to begin with.
@@JoaoGauss you absolutely have a good point. However, you also have to look at risk calculations. The risk to blue-collar workers to take on a new product is very low. If the product fails, even if the worker loses thier job, they are still entitled to severance and/or unemployment. However the risk grows and compounds with each level of management up to and including the owners of the business who have the highest level of risk. I'm all for profit sharing, but there is no question that the CEO/owner should be getting a lot more share of the profits than an average worker. Not to mention that many businesses should be reinvesting in their profits into their employees/business instead of lining their pockets.
@@JoaoGauss you are minimizing the risk that owners take while overstating what blue collar workers go through. When a business fails, workers are laid off, not fired. Depending on the situation, they are typically given enough wages to last for 6months all the way to 2 years.
The mechanism is both elegant yet high complex, and understandable thanks to all the detail and props Steve included. Well done!
I actually used to design different models for these types of "gas" pumps back in the day. You can probably tell how different & less bulky more recent models are and thats all thanks to years and years of improvement & fine details changed. I can also confirm that the little air gap in between the valve & cavity of the membrane is very crucial and probably the most important part of this whole device. Cheers!
The fact that this is all done mechanically and not electronically is what makes this so cool to me
Many principles that would function forever with repair that a craftsman can do will be replaced by digital stuff that needs from now on monetarized upgrades from above. That's cool for the big players.
can it make the fuel free?
Want your mind blown? Look for videos on mechanical targeting computers.
I wouldn't be surprised if there are electronic components to some these days or in the near future.
But these automatic shutoffs long predate the cheap and widely available integrated circuits we have today to enable us to computerize everything. These cutoffs were used before electronic displays became common.
/I had always assumed it was based on a float, though
yes, when most of the technology is becoming less mechanical more electrical, this piece of tech remains the same;)
I have worked as a mechanic and as an electrician for most of my adult life. Part of the fun of these careers is trying to figure out how things work. Most are pretty easy, however, I can remember a few times while pumping gas into my car that I thought about how those nozels worked. I thought a ventury and valve might have been involved, but never was able to tie it all together. Thank you for clearing all that up...Its always nice to see how things work. Well done!
Part of the fun?
I never open anything up to figure out how they work because of the anxiety it causes me knowing that I am invariably going to break something or not be able to figure out how to put it back together.
nozzle, venturi. and yes, it does matter.
@@dannyarcher6370 That is why you only do that with stuff you don't really care about or that is already broken. I never throw any device away before performing an "autopsy" on it.
Though, I would still advise doing some research before dismantling something. Knowing about compressed springs, dangerous capacitors or possible toxic substances in certain components can save you a lot of pain.
Besides, this is YT and it has its own version of Rule 34. If it exists, there is a video YT video of someone dismantling it.
@@TheCorintur Back when I was a kid in the 50's and 60's I used to drive my parents nuts because I took just about everything apart and tried to but it back together. I succeeded most of the time, but there were a couple of times I made things a lot worse. We didnt have youtube back then and the stuff in the libraries was vague at best. I grew up trying to fix everything I owned and never threw anything away. As to compressed springs and stuff like that, I had a couple go flying across the room, but you learn to be careful over time. And yeah, I now have a ton of junk stacked in my garage from all the fixin, but now, I can call them all antiques and sell em on ebay!
@@dannyarcher6370 That's why you're not an engineer
I'm so satisfied when there's no electronics involved... Nothing but pure fluid-mechanical principles in action. Ingenious! And you're such a good teacher!
Thanks for this fantastic explanation!
I used to work at a petrol station for 3 years and always wondered what was happening. Especially since we used to fill for the customers and on some occasions the pump would either constantly switch off despite not being full or fail and continue to overflow. It was never the pump itself as it would only happen with the single customer but now I'm wondering how the shape of the tank or angle of entry would affect it. I now know when people pulled up with the tank on the wrong side and we would have to stretch it around and have it pour from a 90° angle, why it would tend to overfill. You begin to learn the sound of when it's almost full out of repetition.
The fact that you made a see-through, 2D version makes me unbelievably happy! Well done good sir
Steve always makes see-through 2D versions!
Luckily this is not Matt Parkers channel. His stuff is great too, but he would make a 4D version that clarifies nothing.
@@agurdel haha, excellent comment!
This is one of those things I've probably wondered about 100 times while pumping gas, but always forget about by the time I get home so I never looked it up. I'm glad you have finally answered this mini-mystery, and done such in a way that is intuitive and easy to understand!
I always assumed it was probably some sort of electronic sensor, but this is far more clever!
i recently started driving,infact got my license on 14th of this month,and wondered about this question only a few days back.
I thought the European model would be much smaller considering they are pumping Liters and not Gallons.
@@TIMEtoRIDE900 Maybe the pressure (flow) is just much higher in the USA? So that it takes the same time for a European to fill up the 40 liters tank of a shoe-sized Fiat Punto and for an American to fill up the 40 gallons tank of a Ram TRX monster.
Haha! Me too! And my work mate also. We discussed this just the other week. So now, rest at last.
@@herrakaarme It varies between gas stations (USA) sometimes you get a slow pump, very rarely you get a REALLY fast pump, and if you pay inside the last gallon delivered goes SOOOO slow! like they don't want to give you an extra penny's worth.
When I fill my boat it doesn't "trip" the shut-off so I have to listen for a slight gurgling and shut off myself or it spills several OZ on the swim deck. It's because the filler tube is 2 1/2" (60mm).
"So I bought this thing and cut it in half"
-Steve Mould literally every video
Steve; I've got to say, when I saw all your models and the title of the video I was confused on how any of it made sense! But the way you explain it all makes everything fall into place, it's very impressive!
I am no engineer, technician or mechanic, but I have been taking things apart all my life to figure out how they work. Thank you for explaining it all so well.
Maybe you should be?
Did u put them back together afterwards?
@@maximus1992a he didn't say he was a puter back togetherer.
@@maximus1992a People like you break my heart. Imagine shitting on someone's interest because of the way that they expressed it. I despise nit picky sarcasm like this.
I like to take things apart. But, when i try to put it back together, i always get some extra screws.
I respect the tremendous amount of time and effort you put in to the making of visual tools that you use to explain. There were at least 2 glass tubes, that green and red pipe stuff, the sawn in half nozzle, that mock up of the sawn in half nozzle and possibly more. Yet somehow, all I could do was to like, sub and share your video to my social media. I few that what I do isn't proportional to the amount of work you put in to this video and that is why I have mad respect for you. I thought I was a huge nerd, but I think I found a bigger one in you.
I wouldn't worry too much, he's getting paid hundreds of thousands from TH-cam for all the views he's getting from these videos. It's a full time job that pays very well.
@Brian Merritt It might be lucrative, but that doesn't negate the amount of the effort that went into the video.
Sometimes the ability for a TH-camr to turn their videos into a career is at the whim of the mysterious algorithm.
@@briandmerritt No, he's really not getting nearly as much money from TH-cam as you think he is. He's almost certainly getting most of the money for this video through Patreon. Most TH-cam users don't realize this, but TH-camrs need to have several sources of income (TH-cam, Patreon, sponsors, merch, etc) because no one single source will provide enough money on its own.
If you really want to do more to support the channel, consider contributing as a patron on Patreon.
All my life I’ve spent half of my time at the pump wondering how this worked!! Thanks for finally letting me know 😁
As a native Spaniard, I naturally have all my google settings including youtube set to Spanish, I was confused when there was a robotic voice narrating everything you were saying with such precision so I thought it was part of the video. I then noticed the option to change the language of the actual video. I have never seen this before. Whether it was done by you or youtube, its a great addition to videos, specially for those that have trouble with english. Good job man!
*Standing Ovation* This was an incredibly thorough and intuitive explanation. Thank you Steve!
Welcome to the channel!
A M A Z I N G
If somebody could understand and explain quantum physics, it’s this man. Thanks, Steve, amazing, as always.
@@GuyJustCool For those topics, I think ScienceClic does the best job one could possibly do.
I tell you, if my professors had been as dedicated to explaining the venturi effect as you did in this video, I'd probably have picked up on a significant amount of the things they were teaching me. A lot of how aircraft work, is based around the venturi effect and the bernoulli principle because the one thing aircraft have in abundance, is air moving rapidly in a single direction lol.
Yes, the principles discussed here affect the functioning of wings, pitot tubes, traditional "six pack" instruments, etc
@@julianbrelsford yep, and the applications only scale up the bigger the plane gets! I have disassembled something so many times and found a venturi of some flavor or another so many times!
My fluid mechanics professor would kill me though if I were to tell that Bernoulli principle can be explained by conservation of energy (such explanation is limited and works only in some specific cases)
Venturi effect is how carburettors work, too.
@@julianbrelsford Unfortunately wings do not fly because of bernoulli's principle (and as such the venturi effect), its a misconception.
Wow, I guess that's why ytube is so popular. Dude you have put an insanely amount time into making this vid
I really, really enjoyed this, thank you for taking up your time. As engineer it was quite enjoyable to see Bernoulli Venturi in action in such a device
I never thought this nozzel was such a "master piece" of a design. Thanks a again and keep the hard work!
Your vids help me learn physics in a way my college classes couldn't. Even though this was a lot to follow and kind of hard, it all clicked in the end and I feel so excited to know how this system works 😊
I used to run a station, so I knew how they worked in general but interesting to see inside the pump. What I can say is this system is so sensitive that as pump nozzles get old and that hole is slightly burred over it will keep clicking off.
So that's what happens when I fill like half a gallon and the thing just stops, over and over.
I have one particular car ('95 Toyota Camry) that has problems with constantly shutting off prematurely at several different gas stations, while my other cars have no issues at these same stations. Your comment about old handles makes me wonder if there's some defect in the top of my tank that exacerbates this problem.
@@jasonbailey9139 Exact same problem here, different car.
Wondering if there's something about the neck of the tank leading up that restricts the relief hole...
@@jasonbailey9139 Same. My 2015 Tahoe does this often. I never thought to correlate it to pumps, as I just thought it was my vehicle.
@@jasonbailey9139 The fuel tank in my Toyota MR2 being high up relative to the filling point meant the curve of the filling pipe was such that the fuel didn't always run down as fast as was needed, causing this exact problem of the valve in the handle repeatedly closing. Lifting the pump handle slightly out or not filling at full speed (part pressing the lever) solved it for me in every case. It only happened at some stations, likely due to them having slightly faster pumps. If it was purely related to burring I would expect it to only apply to certain pumps at certain stations and not every pump at that station.
I love these kinds of (fluid)mechanical solutions to problems. They always seem so intricate, but built off such simple elements. Great design, great video!
And so robust , too!
WONDERFUL!!! I spent all my life wondering HOW IN THE HELL this stuff works!!! But thanks for this absolutely magnificent explanation, I finally got all the deep secrets and science hidden behind this nozzle!!! And it's amazing the big amount of work Steve had to assemble all of those devices!
Thanks, Steve, you're a great man! 👋👋👋👋👋👋👋
Thanks for explaining something that I briefly wonder about when filling up, and then forget about when I drive off. Now I will always know what happens!
You have a great style of making these videos.
1 - You really struck gold with these 2D models, they show everything so nicely and without clutter
2 - You explain things in multiple different ways, which is helpful when someone doesn't get it the first time, and then would be confused for the rest of the video
So thanks for showing off clever designs and physic principles in this way :D
I don't usually comment on videos, but this deserves appreciation... Thanks Steve! That green and red model was amazing! To remove complexity with simple models is an extremely difficult thing to do and you nailed it here! Thanks again!
@Human-6358 Don't waste that amazing chance of making a 1-minute long video with as much information and clear didatic as this one here. You'll become famous, go for it!
I would agree ... if I could see green and red :-( but it is a good video.
I was hoping we might understand why US have the auto stop filling mechanism but we don't have this in UK.
@@stephenhookings1985 that's weird as I've seen this in Germany and Switzerland, also maybe im France...
@@stephenhookings1985 We... do have it in the UK. At least where I am.
Steve has a real gift for explanation. He is so good at taking complex stuff and breaking it down on a level that can be meaningfully understood by both a professional and a general audience.
Steve Mould,
This was very helpful thank you. I now understand why gas may not come through during hot weather. Gas expands with rising heat, and understanding how this nozzle works is enough to see why the expansion of the gas would make it much more difficult at times in high heat areas with certain types of nozzles.
Excellent job Steve! I had a vague understanding that a Venturi principal was at work here, but never understood how the then nozzle would shut off then reset. Well done!
I'm a mechanic by trade. Can't say I've ever known how these work. As soon as you started on Venturis it all clicked for me, seeing carburettors work using the same principal. It's all clear now thanks to your great explanation. Thank you!
Exactly the first thing that struck my mind when i saw the Venturi model.
I thought of carbs too but only because of smarter every day
can it make the fuel free?
The venturi is only 1/4 of how this works. The mechanism that changes the fulcrum is genius.
"It all clicked." NICE PUN
I have been wondering how this happens for SO LONG now, every time I visited the gas station in fact, but never got around to reading about it. You sir made my whole week! Thank you SO MUCH
Same here, glad I finally know!
yeah, this was a GREAT explanation of how these mysterious devices work. I've always wondered how those worked... now I know!
I am also someone who ALWAYS wanted to know, always wanted to look into more every time I was filling it up. I guess I was meant to wait for this video to come out! Cause a lot of this would have went over my head without the visuals and in depth explanation. Life is trippy and great!
Me too, even if I had researched how it works I don't know if I'd have understood it as I did with this video!
what a great video sponsor! thank you for teaming up with them - helps me a lot as I am questioning the purpose of my job.
Was waiting for this! Extra kuddos for that satisfying tone in your voice when you explained the ball Bearing moving inward.
I always tried to design it in my mind, I thought the petrol was supposed to run back up the sensor line because of low pressure (that part I had) never would've thought it could be mechanical though. Blows my mind how clever mechanical designs can be; I'm a computer engineer but sometimes I think the ease of electronics can make use lazy design-wise
I'm currently in college for computer science myself and I wholeheartedly agree, the fact that I can tell my computer to remember a number rather than having to design a complex mechanism that holds memory is incredible, and also feels incredibly lazy after seeing mechanical engineers do their thing 😂
I agree, mechanical engineers nowadays are very tempted to use arduinos for every solution instead of designing an elegant mechanism that does the same thing
Thanks Steve, in a roundabout way you've solved one of my life's great mysteries: Why is it so darn hard to fill a small can of petrol. There's a minimum flow of fluid required to prevent the mechanism from shutting off the flow. My strategy is to pull the lever fully to set the mechanism and then to ease off but if I go to far there's a click and no flow. Very frustrating trying to fill a 5L can.
There's always the tried and true way of waterfalling it into the can. You can press the ring on the outside of the nozzle (if it has that safety feature) by hand and just hope you don't spill
Obviously I don't recommend doing that, as it circumvents multiple safely features, but it works
Part of the problem I think is that there isn't much space between the nozzle and the sides of the opening to let air flow into the can, then up the venturi tube. This means that the pressure relief provided by the valve is less effective, which actuates the stop.
Use a funnel
Man’s making Molotov cocktails at the gas station
the trick is not to insert the nozzle too deep... just the tip.
Incredible. I've always wondered how these work. Basically just a change in leverage by using the venturi effect. Crazy how simple/complicated that is. Nice work! Love your videos.
An excellent video, thanks. I read written explanations and could not follow what they meant. Your video made perfect sense even for a person with no previous knowledge of the science / technology involved.
Amazing. I love it when they manage to make things react to the environment without needing electronics.
Why?
@@misterman3187 just because it is low tech, mechanical. Electronic is the easy way out, more exspensive though. Not saying electronic is bad, just that many mechanical designs just take more science to work, not just sensor goes off and then close valve.
"It's mechanical machines, son. They react to physical events. unlike the digital do-hickeys you youngsters use these days. They're reliable, easy to produce, and easy to maintain"
Do as the Romans do.
@@cbpe1234 That is... an oversimplification to say the least. Electronics and mechanics have their own place, there is no easy way out. Sometimes the mechanical solution is simpler, sometimes not. Sometimes electronics last longer, sometimes not. The aspects you need to look for in every case is the cost, lifetime and cost of assembly and repair. Like you can ditch a limit switch and install a Hall effect sensor but it costs 10 times as much, but also the life went from a couple million cycles to a couple billion. But you won't do that in a 50$ kid's toy. It always depends on what you need exactly.
Amount of effort you put in to explain this, is incredible
Took me a few times to understand this, but once you get it, makes so much sense, and its so much more simpler than expected
Pretty complex mechanism. I always thought it's somewhat simplier. Very good vid Steve.
Its very simple mechanically if you think of the two parts as a sensor and a signal not to mention whatever it takes to close the valve. These gas pumps basically take a three part problem and use two mechanisms to solve all three. The beauty of the design is that both operate with only fluid dynamics. Most other sensors require a bit of chemistry or some other physical property (to detect a chemical presence) and a bit of electricity (to transmit the signal) as well as moving parts to operate the valve.
@@glumreaper8885 If it was so simple, in the old days they would have used the system to fill up their horses.
It is simple. Basic pipe fitter knowledge
@@LordZordid i tell ya son in the ol days we filled arr horses witha notha type of pipe and we damn well knew when to stop
I've loved your 2D models of fluid dynamic things series, and this might be my favorite one yet because it's about an object most everyone is familiar with/has used, AND it's so complex and cool. Nice one!
Excellent explanation and demonstration. Always wondered exactly how it works.
The click always sounded mechanical (not electrically switched), and always though it's got to do with some back pressure on the petrol flow.
What an elegant solution using the venturi effect of the *air* flow to control the valve.
a 13 minute video to explain a nozzle that we all take for granted really shows how much thought went into making these things.
I really appreciate what you do with these models. As a teacher I know this takes a lotta time to make the best one to show the audience.
I was about to write this same comment.
Someone should produce a set of practical models for demonstrating the most common principles in fluid dynamics. Like the ones Steve made himself for the pump nozzle. A practical model, that maybe even every student gets to test themselves would be much more engaging and easier to understand.
@@Renee_R343 You, Sir, are a genius.
I work in the fuel industry and have often wonder how nozzles work, thanks for explaining it. The physics that go in to a common place item that most people would never ever wonder about how it actually works is amazing.
ive always wondered how this worked because i am enough of a neurotic to worry that i cant trust it and it spills over and oh god its shooting out of the tank and onto my pants and oh god now theres a puddle and OH GOD I DONT KNOW WHY BUT NOW EVERYTHING IS ON FIRE MY CAR IS BURNING THE GAS PUMP BLOCK IS BURNING AND I TRY TO GET AWAY BUT THE GAS STATION EXPL-
I imagine most people have wondered how it works. I had an idea it was a venturi effect but I wasn't sure how it operated.
I love this channel because it answers the question every high school student asks repeatedly. “When am I ever going to use this stuff?” The answer, is every single thing you see in your everyday life is an amalgam math and physics. Most tend to take it for granted because the students who found the answer to that question make it all possible.
@@Leonarco333 The smartest 1% make the stuff the rest of the idiots get to use and claim credit for.
@@stopthephilosophicalzombie9017 accurate. Sad, but accurate.
The ingenuity of these things are amazing ... I always wonder who came up with such a complicated, yet beautiful design that simply works mechanically ... Fantastic :-)
What a great video. Easily one of the best illustrations of mechanics of this device. I was looking for something else but quite enjoyed this and followed your channel.
If you want the membrane in your model to flex more, an easy way would be to make it more "3D" (You'll notice the membrane in the actual nozzle is a big circle, not a thin strip). This will help for two reasons. First, more area for the pressure to act on means more force on the membrane. Second, larger things are easier to bend than smaller things, because the force has a longer moment arm. (If you've ever snapped sticks for firewood, you'll know it gets way harder to snap halves into quarters than it was to snap the whole into halves)
I was assuming it was also just how constricted the Venturi tunnel is. You’re starting off with a pretty high pressure and then you’re pushing the liquid through a very small space. Smaller space = more speed, more speed = larger pressure drop. But I also don’t know much about fluid dynamics that was just one of the things I noticed.
@@Bllksem that would also have an effect, because it would change the pressure acting on the membrane. It's just a harder change to implement on the model than my suggestion
Its just as easy to flex regardless of size, size is not a material property. What changes is the total amount of deformation. The same way a 1 cm long rod of steel pretty much doesnt change its size when heated/compressed/tensioned (visibly) but a 1'000 m rod of steel would massively change in lenght, 100'000x as much. So instead of eg. 10 µm it would be 1 whole meter longer/shorter.
@@leocurious9919 ... yes, I simplified the material mechanics in my explanation. But given that we're talking specifically about total deformation instead of strain, I just skipped to total deformation. Also, I clearly meant "for a given force", not "for a given moment". You would be correct for axial force, but this is shear force and bending moment.
Also, the specific scenario at play - bending of a plate (technically a membrane, but that's just a very thin plate) - *does* actually care about size and shape. Bending is (approximately) quadratic with length, not linear, and plate deformation is heavily dependent on the shape of the plate.
@@elekbuday81 You are of course right, it is not linear with size. The forces keep adding up, they are not constant. An error I made while posting a quick reply, trying to correct you.
I used to rebuild these nozzles as a teenager. I found it fascinating trying to figure out the engineering behind all of the components. Steve, the only thing you forgot to include is the fact that the part of the mechanism that locks using the bearings is also affected by the pressure of the fuel itself. That is why you cannot open the valve until the pump has engaged and built pressure in the system.
Nope! There's no fuel into the bearing lock! If so, the positive pressure under the membrane will push to up and will disengage the bearings! And also the pump wont start until you pull the trigger lowering the pressure into the hose! Well at least in Europe work in that way!
@@MyNotSoHumbleOpinion Interesting. In the US, you can clearly tell that the valve in the nozzle does not open until the pressure in the hose has built up. There is a part of the nozzle that uses that pressure to help engage the bearings allowing the valve to open. I'm not suggesting that fuel enters the bearing lock itself, only that pressure from the fuel in the line affects that part of the mechanism allowing it to engage the bearing lock.
@@MyNotSoHumbleOpinion Here is another video that explains the safety feature I'm talking about very well. The part I'm referring to is discussed starting at about the 1:20 mark. th-cam.com/video/q3phjAQZdGg/w-d-xo.html This is the part that I was mentioning to Steve.
@@TheNextThing Yes, maybe it's slightly different! In Europe the trigger can remain pulled, but the internal mechanism is disengaged! You can put the pistol in the pump with trigger locked, but no flow until you reset the trigger back to open!
So now I'm curious about different countries technology: how the pump know when start to build pressure in the hose? There's a button on the pump?
@@MyNotSoHumbleOpinion Yes! I didn't realize things were so different either. On our pumps, we pay, then we select the fuel grade. After that, you wait for a few seconds for the pump to pressurize. Then you can start pumping. Until the pump is pressurized, you can pull the lever as much as you want, but the bearing mechanism won't lock. So I usually have to keep pulling the lever and letting it go until it has pressurized.
seeing the whole logical process actually work is beautiful. actually being smart enough to engineer these kinds of things would be so satisfying.
Great video with very good illustrations and descriptions. I always had some idea of how I thought it worked (I assumed some sort of cam and/or clutch mechanism paired with some kind of air pressure sensitive system) and it was nice to finally understand. Thank you for the explanation.
As a crusty old journeyman industrial instrument mechanic, let me say, this is another great video. Steve Mould has such a great talent for explaining these principles that our modern world depends on. Well done!
Leave it to Steve to take a very complicated product and simplify it. I love that I can watch his videos and understand something at the end of it. Thank you Steve I appreciate all that you do.❤
that mightve been one of the most interesting youtube videos i've ever seen and believe me i've watched a lot. spectacular job at coming up with the models to explain the mechanisms. thank you!
You did a good job. A layman explaining principals of hydraulics with no engineering experience in the field is challenging for sure.
Many youtubers wouldn't have taken the time to craft the supplementary models that you made for this explanation, but I am SO GLAD you did. I'm a big visual learner and those models were excellent (and I can tell you had fun making them as well).Thanks for answering yet another question I didn't know I had!
Because many youtubers don't get millions of views like this channel, and it'll be a waste of effort
th-cam.com/video/rhgwIhB58PA/w-d-xo.html
Every heard of practical engineering? He also loves making mini models
As an ex science teacher and lover of great explanations, I reckon you’ve deconstructed and explained that brilliantly. Fabulous work there!
except his explanation for Bernoulli's principle (the most important part) was completely useless. it's exactly this type of hand waving nonsense that frustrates young students and turns them off from science and engineering. you can't explain something with a physical law. a physical law is just a description, not an explanation. conservation of energy is not why the pressure drops, it's just another way to describe that the pressure drops.
the actual reason the pressure drops is simply because the atoms which go through the narrower passage are more likely to have a smaller vector component which is perpendicular to the walls of the tube. in other words, the atoms which happen to bounce into the narrower section are those which on average are moving forward not sideways. aka they are hitting the walls of the tube with less frequency and with less force so the pressure against the walls is lower. basically the narrowing of the tube filters out the particles that are likely to contribute much to the pressure against the walls of the tube.
it's not because of magical calculations that dictate that "it simply must be so or this law would be wrong!". no. it's just geometry.
As long as I can remember, I have always wondered how these things knew when to shut off! Thank you for an excellent explanation !!
So complex, yet you made it easy to understand. Thanks Steve.
The illustration of the ball bearing lock thing you made in 2d is almost an exact replica of the internal parts of an mp5!
The mechanism works to delay the opening of the chamber until the bullet has left the barrel so the pressure can drop to safe levels. The green pointy part of the mechanism holding the rollers outwards has its point facing forwards, and the red ramps are full notches instead. When the gun fires, the recoil passes through the part that’s locked and pulls backwards the pointy part holding the ball bearings in, then once unlocked, the whole mechanism goes in the opposite direction than in the video, starting the process of cycling the gun.
Sorry for the rambling. I just think it’s really cool to see not only interactions, but full mechanisms in completely different fields!
Exactly! Roller-delayed blowback was the hot shit for a while, and basically anything the former Mauser guys at Heckler & Koch ever did. G3, MP5, HK33, HK21, P9...
So next up: Steve cuts a mp5 in half :D
Thanks, now I can make my own mp5!
I have heard of mp3 and mp4 format, but wth is mp5?
@@margue27 a gun
i'm happy to see any time steve cuts things in half
i needed to know this. it’s bothered me for years, and now the answer has been delivered in a nice neat package.
Just glad there are people like you who actually understand what is going on so smooth brains like me can enjoy these inventions.
As an engineer it doesn't surprise me how it works, it surprises me how it keeps working reliability.
Exactly. It relies on an airtight seal and lots of moving parts. I'd expect these to fail all the time but that clearly isn't the case.
it has been, well, engineered to work reliably . . . through many, many generations of accidents, fires, and small improvements to iron out every last wrinkle. With time, good designs succeeded, and bad ideas were melted for scrap. It's not like they did it precisely this way from the beginning.
Scale helps: The fact that every petrol station needs a couple of these, and every small town has at least one petrol station or more, means that the budget available to engineer these things has been "sufficient".
@@JurekOK and this is what amazes me about engineering. the fact that it continuously improve to be better and better every time to the very limits of what physics, and chemistry allows us
Sometimes though, you run into pumps that keep clicking off 5 seconds later.
Seems like they fail "safe"... If you've ever had a super touchy nozzle, you know what I'm talking about. They're designed so that if they fail, they fail to off, not on and flowing.
I've looked this up before and only *kinda* understood what was going on. Just a couple of days ago I was filling the tank and got to wondering again - so glad this popped up for me! This is an incredibly detailed explanation - I love the cutaway models you make for your videos to really break down complicated 3D concepts into 2D, it is so helpful as a tool to see those. Well done, I always learn so much from your videos, and show them to students and other education professionals.
This is one of those things I’ve always wanted to know but never bothered to find out and luckily this vids popped up on my recommendations - how convenient
I was always curious on these pump nozzles, thanks for fulfilling my curiosity and such a good explanation
That changing fulcrum concept is really interesting. I noticed similar constructions in automatic circuit breakers, as safety in firearms and in (photographic) leaf shutters. I always wonder how such things were calculated in the past and now it's done today.
Excellent explanation. It was worth the effort you put into that illustration. Thanks to that I have understood perfectly how something that I always ask myself works. You have made all of that seem so easy now, and it really is, but to most of us it seems more complex than reality. Thanks and greetings from Tampa, Florida.
I know! I was thinking "wow, I actually understand this model that he made."😂 Give him much props for that 👌
I totally agree. I'm so impressed that he built the models & presented the effect so clearly. Very interesting - I'm a fan now.
ANY WAY TO CHEAT ON IT?
I don't agree. 13 min video to explain 1 minute thing..
Excellent explanation. Just last week I experienced a gas pump that failed to automatically click into the off position resulting in a minor overflow and spill. The truck in front of me at the pump was taking an abnormally long time to fill. When I pulled into the pumps for my turn the result was the same. It was *very* slow. As the tank filled up it did not shut off and ended up spilling down the side of my car. I spoke with the station attendant and she said the low pressure at the pumps was due to filters in the pump that needed to be replaced and as it was a holiday weekend there was no one available to do it. Thus the low pressure coming out of the pump must not have been enough to trigger the shutoff. Enjoy your videos. Cheers from Canada (PS the title reads "How petrol pumps know...")
Thanks for your time to made the models and the explaning... very nice!
Wow, I can tell how difficult this must have been for you to explain clearly and succinctly, and your added models knocked it our of the park!
it is something quite complicated but the Venturi effect, Double Lever latch and the bearing locks are all pretty common in everyday engineering. In fact most of engineering all follow basic principles but they're just carefully engineered to work in real life instead of only on paper.
Fun fact: your toaster uses electromagnets to keep the spring down. the amazing bit of this electromagnet mechanism is that the lever that you push down has a piece of metal attached to it, and when it goes all the way down it connects the main and the toaster circuit and powers up the toaster. when the toaster is powered up it keeps that metal in place, and its built in timer will cut out the power to the electromagnet. Hence why you cant lock a toaster down when its not powered.
The way you explained and showed the fulcrum and how it's point changes explains everything about WHY it feels different to try to pump when there's nothing flowing through vs. when gas is moving through it. Put into words and imagery what I've intuitively felt for most of my life. Bravo!
you took a very complicated, hard to understand concept, and you made it very easy to understand. Good job.
The "sword" and circles you used at about 8:30 is interesting to me, as it's a roller locking mechanism, which is used in some firearm designs, like the MP5 or G3, though in the MP5 it's not actually locked but "delayed" by this mechanism.
This is so amazing.. a few days ago me and my nephew were having a discussion on this on how we thought petrol nozzels worked... and ofcourse weren't sure of it.... and i see this video today that explains exactly how they work. In the begining of the video i was thinking to myself this is way to complicated for me to comprehend.. but by the end of it i now know exactly how they work... thank you so much... such an amazing teacher... LOVED IT......
What an amazing piece of engineering. Thanks Steve for explaining this!
and just like every other "amazing engineering" it has fatal flaws. Certain gas tanks when that purge valve gets stuck, you have to pump 25-40c of gasoline at a time, taking you a total of 35 mins to pump a full economy car sized tank. Search "gas pump keeps shutting off" on youtube....
@@crisnmaryfam7344 I would take that as a safety feature, if something is broken you can't spill gasoline
@@crisnmaryfam7344 It happens from time to time, but it's not a problem (even less so when you know how the mechanism works). Just position the nozzle so it doesn't happen. You're welcome.
@@crisnmaryfam7344 If the pump works for almost every tank out there, then I'd say your tank is flawed, not the pump
Simple answers are admirable in design, but it's equally impressive to see complex devices like this! Didn't think about all this hiding in such as commonly used item.
I've always wondered how this worked. Fascinating. Thank you!
This is such a clever combination of principles but the most impressive thing for me is the way it was explained. This is the best step by step breakdown of any educational topic I’ve ever seen. Not one of the best, the best! Every time a side issue that could have scuppered things arose it was dealt with before it could be a factor that might throw you off course. Congratulations on this level of understanding of not only the things you are explaining but also the human learning experience. Top class!
I love how creative people had to be to come up with solutions to problems, that previously probably were just accepted as something you had to deal with.
oh shit, you here?
AND, now these problems were all solved _WITHOUT_ computers, or even electricity!
Oh nice, I was always worried about overfilling my tank for some reason and it's good to learn how this stuff actually works to alleviate those worries
It's common to say TH-cam is mainly a trash bin (I'm the first to repeat this refrain over and over). But beneath the common trash, those kind of videos which gives a glimpse of what Internet could be (what internet was intended to be). To share knowledge, elevate all of us (on any king of subjects, arts, sciences .....). This format is exemplary.
TH-cam finally recommended me this - no clue why it took so long. Amazing video, great explanation, hat off for the huge effort you put into making the models.
Stunning production value overall. Definitely new subscriber here 🤓
Thank you so much for this. I think about this ALMOST EVERY TIME I fill up my tank and have never known how it works. What a satisfying mechanism, too
Thanks a lot!
Plenty of work, efforts and passion and the coolest explanation and tuition video as a result.
That was an amazing explanation, I don’t think it could have been better! Nice work!!!
As a software engineer, I think hardware engineers are so much cooler. You have to understand how the world works on a completely different level to make cool new designs.
yes we are, but software is like magic. And to us most of you are magicians :).....
.... until you come to our dept. and say "it doesn't work, it's a hardware problem"
@@WalterBurton The act of programming is a part of Software Engineering, but is not the entirety of it. Software Engineering includes elicitation and documentation of formal requirements and specification, various forms of testing, auditing and reviewing of existing code or software, application of various formal methods, etc. It's a common misconception that Software Engineering is merely programming, but programming is just one small part of the practice of Software Engineering.
@@WalterBurton I used to chat with a supercomputer sysop whose job title included the word "engineer". He knew exactly where he stood on the grand scale of qualifications, but he used his title to tease his wife because she was a fully qualified civil engineer. ;)
But seriously, programming is a form of engineering and I wish the world could afford to train the average programmer better, if that makes sense.
@@WalterBurton "please"?
Hi Steve. I work in the 'petroleum' industry calibrating these gasoline or petrol dispensers. Many new techs ask how this device works and now I can send them here to answer their questions in a very informative scientific way. Great job. Thanks.
one time I had a gas pump repeatedly shut itself off even when my tank was near empty. I was getting really frustrated so I moved to a different pump after trying like 4 times. It worked perfectly.
Now I realize the tube was probably clogged by debris or intentionally by some vandal. great video!!
Always wondered how these worked. It's an astonishingly reliable mechanism. Having worked in a fuel station I have seen them fail to stop on occasion. mostly in the winter months.