How gas pumps know when to turn themselves off 

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? The sponsor is 80,000 Hours: head to 80000hours.org/steve to start planning a career that is meaningful, fulfilling, and helps solve one of the world’s most pressing problems.

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.

The fact that this is all done mechanically and not electronically is what makes this so cool to me

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.

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.

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…

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.

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!

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!

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

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.

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!

The mechanism is both elegant yet high complex, and understandable thanks to all the detail and props Steve included. Well done!

The fact that you made a see-through, 2D version makes me unbelievably happy! Well done good sir

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!

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!

"So I bought this thing and cut it in half" -Steve Mould literally every video

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!

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!

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.

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 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.

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.

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!

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!

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 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.

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!

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.

Was waiting for this! Extra kuddos for that satisfying tone in your voice when you explained the ball Bearing moving inward.

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!

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!

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!

a 13 minute video to explain a nozzle that we all take for granted really shows how much thought went into making these things.

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 love these kinds of (fluid)mechanical solutions to problems. They always seem so intricate, but built off such simple elements. Great design, great video!

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

I've always wondered how it worked, but never expected it to be this interesting! thank you for simplifying the mechanisms and letting me understand it. So interesting!

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.

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 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.

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! 👋👋👋👋👋👋👋

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.

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.

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.

So complex, yet you made it easy to understand. Thanks Steve.

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.

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)

Amazing. I love it when they manage to make things react to the environment without needing electronics.

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 :-)

Amount of effort you put in to explain this, is incredible

Pretty complex mechanism. I always thought it's somewhat simplier. Very good vid Steve.

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.

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.

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!

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.

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

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.

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!

As an ex science teacher and lover of great explanations, I reckon you’ve deconstructed and explained that brilliantly. Fabulous work there!

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!

As long as I can remember, I have always wondered how these things knew when to shut off! Thank you for an excellent explanation !!

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!

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!

You did a good job. A layman explaining principals of hydraulics with no engineering experience in the field is challenging for sure.

It's common to say RU-vid 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.

i'm happy to see any time steve cuts things in half

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.❤

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.

seeing the whole logical process actually work is beautiful. actually being smart enough to engineer these kinds of things would be so satisfying.

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!

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.

Just glad there are people like you who actually understand what is going on so smooth brains like me can enjoy these inventions.

That was an amazing explanation, I don’t think it could have been better! Nice work!!!

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!

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.

i needed to know this. it’s bothered me for years, and now the answer has been delivered in a nice neat package.

I was always curious on these pump nozzles, thanks for fulfilling my curiosity and such a good explanation

As an engineer it doesn't surprise me how it works, it surprises me how it keeps working reliability.

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......

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've always wondered how this worked. Fascinating. Thank you!

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.

What an amazing piece of engineering. Thanks Steve for explaining this!

Thanks for your time to made the models and the explaning... very nice!

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.

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.

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.

This is amazing. I never knew that little pump handle had so much science and engineering in it.

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

As a sales engineer I find it amazing how you drive us through the explanation and build up the complexity of it. I'm learning more than just how gas pumps work!

1:35 these kinds of things started making a lot more sense when I started thinking of air as if it were "sticky" or self-attracting. Moving air "pulls" on surrounding, slower air. On a side note, I feel like this is worth discussing if only for the reason that it's a device partially controlled by electronics but whose fail-state is normal operation. In an age of techbros coming up with all these high-tech "solutions" to minor problems, it's nice to see something that just works because of how it was built, not because of how it was programmed.

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.

One of the best illustrations! +1 Sub. Kudos to you Steve.

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

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.

Great video! "Must be electronic " reminds me of reprogramming the hydraulic computers in older automatic transmissions. The first ones were devised in the 1940s, many used no electricity up until the 1980s. Instead, they used oil flow and pressure in complex passages called a "valve body" when you disassembled it it looked like a printed circuit board but with a maze of valves and oil passages. They actually made me very good at diagnosing electronics because I could visualize circuits. Pressure was voltage, flow was amps, restrictions were resistance, accumulators were capacitors, check balls were diodes, valves were switches, oil flowed from high pressure to low pressure, and there were relay valves as well. For racing, We would get a kit with new springs for the pressure valves, drill bits and jigs to either drill out new passages or open restrictions, balls to make check valves, and instructions on how to grind slots in valve spools or to adjust their length. As a kid I always enjoyed spending an afternoon doing this (and still do!) By doing these things you could adjust when your shift points happened in relationship to varying engine load, throttle position, and vehicle speed. It also changed how hard the shifts hit. Stock transmissions used lower rpm shift points for economy, soft applications, and actually engage one gear before completely releasing the next intentionally causing slip for "comfort" this causes heat and wear, and was why automatics were called "slush boxes" when they first came out. However, advancements in design soon proved that no matter how good you thought you were with a manual you just couldn't beat a race automatic. Many performance automatics are still based on hydraulic computers to this day. And we adjust them with pressure gauges on different circuits. Whenever they shift, the tires bark and the seat slaps you in the back! I am actually more impressed with the engineers that designed such mechanical devices than the "plug and play" tuning of today. Sure, you can adjust these parameters eaiser, but, it gives you no idea how this is happening inside the device.

This video actually answered another question I've always had about these pumps; which is why the heck is there always so much that drips out after it shuts off. Now i see how large that chamber is between the initial valve and the nozzle. You're gonna see me at the pumps turning that sucker all the way upside down to drain out from now on.