Why does a spray bottle work? • Hacker News Board

Re: Why does a spray bottle work?

#41

Post by MichaelApproved » Sat, Jun 09, 2018, 7:18 PM UTC

vanilla-almond wrote: post #28

A few years ago, a British inventor appeared on a TV show called Dragon's Den (UK version of Shark Tank) and pitched his idea of an improved spray bottle called the Anyway Spray. Instead of a normal plastic tube inside a bottle with an opening at the end, he designed a tube with millions of tiny perforations along its length. This meant the spray bottle could operate at any angle (even upside down) and could empty al…

Why isn't this in everything? I'd easily pay an extra few cents to have this in spray bottles. It's such a frustrating problem.

Re: Why does a spray bottle work?

#42

Post by mbell » Sat, Jun 09, 2018, 7:20 PM UTC

rossdavidh wrote: post #33

mbell wrote: post #26

Earlier quoted context omitted.

> One way valves are basically diodes, but for fluids rather than electrons. The analog of the fluid in that analogy is electric charge/current, not electrons which move in the other direction (which kinda breaks the analogy as a result).

However, I think it would have been quite difficult for me to get the concept of "holes" in semiconductor current, which are positively charged pseudo-particles created by the absence of electrons, if I hadn't been able to think of them as being like bubbles in a fluid. They go the opposite way of the fluid flow, and they are somewhat particle-like. So it's not a totally broken analogy, it does help to clarify some t…

I generally found the fluid analogy did more damage than good for a lot of people in EE school. A lot of people think of electricity as electrons zipping around a circuit at the speed of light due (at least in part) to the water analogy. Having to transition from that world to thinking in charge transfer and fields while electrons move around linearly at a snails pace if at all was very difficult for many people.

I'd bet in a poll of the general public, most people think electrons fly around a circuit like water in a pipe, which is of course completely wrong. I guess it's debatable whether the inaccuracy matters or not. But in general, I prefer analogies that are simplifications and leave out details, rather than those that are completely ass backwards from reality.

Re: Why does a spray bottle work?

#43

Post by SheinhardtWigCo » Sat, Jun 09, 2018, 7:29 PM UTC

vanilla-almond wrote: post #28

A few years ago, a British inventor appeared on a TV show called Dragon's Den (UK version of Shark Tank) and pitched his idea of an improved spray bottle called the Anyway Spray. Instead of a normal plastic tube inside a bottle with an opening at the end, he designed a tube with millions of tiny perforations along its length. This meant the spray bottle could operate at any angle (even upside down) and could empty al…

I know it's for TV but that was a great pitch.

Re: Why does a spray bottle work?

#44

Post by cantrevealname » Sat, Jun 09, 2018, 7:30 PM UTC

btrettel wrote: post #24

anotheryou wrote: post #7

How does the nozzle diffuse?

Fluid dynamicist here who works on the breakup of larger water jets. How the jet breaks up depends on the design of the system. (I assume you mean break up, not diffuse. Diffusion is a different physical process which occurs independent of breakup.) A low speeds (laminar flow), Rayleigh's analysis shows that a simple liquid jet breaks up due to surface tension effects. https://en.wikipedia.org/wiki/Plateau%E2%80%93Ra…

> Fluid dynamicist here who works on the breakup of larger water jets

One of the reasons I freaking love HN. No matter the topic, there are actual experts reading it and willing to comment.

Re: Why does a spray bottle work?

#45

Post by Fnoord » Sat, Jun 09, 2018, 7:31 PM UTC

SimonSword91 wrote: post #18

This is a nice example to show the illusion of explanatory depth [0]. Most people would say they know how a spray bottle works, but fail to describe all relevant details of the implementation, [0] https://www.edge.org/response-detail/27117

> If you asked one hundred people on the street if they understand how a refrigerator works, most would respond, yes, they do. But ask them to then produce a detailed, step-by-step explanation of how exactly a refrigerator works and you would likely hear silence or stammering.

This is a terrible example because its essentially a trick question. The illustration would highly depend on context.

Say you meet someone on the street and you casually ask them this question, or you ask this on a birthday. "Works" with regards to a refrigerator refers to "knowing how to operate", or perhaps the basics.

Whereas if its for the TV quiz program "engineering of the kitchen" or "an applicant for technician repairing Samsung's refrigerators", yes then its clear that more depth is meant.

That's not to say the Dunning-Kruger effect doesn't apply here. Its just that there's a level set for a debate due to the context which then presets also the level of the expected answer.

Re: Why does a spray bottle work?

#46

Post by neuralRiot » Sat, Jun 09, 2018, 7:36 PM UTC

mbell wrote: post #42

rossdavidh wrote: post #33

Earlier quoted context omitted.

However, I think it would have been quite difficult for me to get the concept of "holes" in semiconductor current, which are positively charged pseudo-particles created by the absence of electrons, if I hadn't been able to think of them as being like bubbles in a fluid. They go the opposite way of the fluid flow, and they are somewhat particle-like. So it's not a totally broken analogy, it does help to clarify some t…

I generally found the fluid analogy did more damage than good for a lot of people in EE school. A lot of people think of electricity as electrons zipping around a circuit at the speed of light due (at least in part) to the water analogy. Having to transition from that world to thinking in charge transfer and fields while electrons move around linearly at a snails pace if at all was very difficult for many people. I'd…

The way the analogy was explained to me when i was a student is that the conductor is a hose filled with water, when you open the valve the water comes out instantly at the other end because the "charge" is moving. It was never confusing to me.

Re: Why does a spray bottle work?

#47

Post by gxs » Sat, Jun 09, 2018, 7:38 PM UTC

MichaelApproved wrote: post #41

vanilla-almond wrote: post #28

A few years ago, a British inventor appeared on a TV show called Dragon's Den (UK version of Shark Tank) and pitched his idea of an improved spray bottle called the Anyway Spray. Instead of a normal plastic tube inside a bottle with an opening at the end, he designed a tube with millions of tiny perforations along its length. This meant the spray bottle could operate at any angle (even upside down) and could empty al…

Why isn't this in everything? I'd easily pay an extra few cents to have this in spray bottles. It's such a frustrating problem.

Jumping to the conclusion that everything a company does is calculated and delibarate is a mistake I see a lot of people make, but in this case it’s accurate.

In a business that operates at a scale of 100s of thousands if not millions of bottles sold annually, cents matter and can make up a significant portion of revenue.

With this in mind, there is a huge incentive to get people to buy sooner rather than later and more often. Forcing a small amount to remain in a used up bottle is definitely a benefit to the company even if the product is going to waste. This doesn’t include the cost of implementing something new. I’d imagine a company would do extensive survey based research to understand if the additional customer satisfaction would outweigh the costs/downsides.

If it’s not a conscious decision, it’s a nice coincidental benefit to them.

Re: Why does a spray bottle work?

#48

Post by codeflo » Sat, Jun 09, 2018, 7:39 PM UTC

mbell wrote: post #42

rossdavidh wrote: post #33

Earlier quoted context omitted.

However, I think it would have been quite difficult for me to get the concept of "holes" in semiconductor current, which are positively charged pseudo-particles created by the absence of electrons, if I hadn't been able to think of them as being like bubbles in a fluid. They go the opposite way of the fluid flow, and they are somewhat particle-like. So it's not a totally broken analogy, it does help to clarify some t…

I generally found the fluid analogy did more damage than good for a lot of people in EE school. A lot of people think of electricity as electrons zipping around a circuit at the speed of light due (at least in part) to the water analogy. Having to transition from that world to thinking in charge transfer and fields while electrons move around linearly at a snails pace if at all was very difficult for many people. I'd…

That's an interesting experience. I'd say that the idea people have about water in pipes is probably overly simplistic as well, and an analogy to an equally poorly understand concept can't help very much. To pick up your example about electron speed vs. signal speed: Water pressure is transmitted at the speed of sound, which is much, much higher than the speed of water flow -- water taps wouldn't work otherwise.

Re: Why does a spray bottle work?

#49

Post by fireattack » Sat, Jun 09, 2018, 7:49 PM UTC

davidkuhta wrote: post #21

I found his write-up on MBTA bus mirror positioning to be a short but interesting read as well: https://alexanderellis.github.io/blog/posts/mbta-bus/

From the map I can't tell how the bus can "go through Bennett Alley and continue straight into the bus tunnel".

The streets are not aligned, are they?

Re: Why does a spray bottle work?

#50

Post by deltron3030 » Sat, Jun 09, 2018, 7:59 PM UTC

jstanley wrote: post #11

anotheryou wrote: post #7

How does the nozzle diffuse?

I would guess it's just a fine mesh that the liquid is forced through.

It's just a hole. If you take a hot needle you can widen the hole of spray caps and increase the throughput (and size of the throw if you also increase the distance to the object).

Another trick for spraypaint bottles is to stomp them vertically if you run out of spraypaint, it won't hurt the system that takes your cap, and gives you little bit more paint.