Rain Gutter POWER #5 - Bell Siphon Fundamentals and Pitfalls

in this build we're getting a better understanding of bell siphons by trying one in the hydropower setup on our rain gutter as many of you predicted in the comments getting power from rain gutters involves a lot of cleaning and even with relatively clean gutters a few weeks without rain can quickly turn into nasty standing water yeah it kind of looks like i peed in but now that summer's winding down it's time for a fresh start so we can tackle some of the awesome suggestions in the comments by the time we got to part 4 the rainy season was tapering off to get the same flow we installed a flush valve from a toilet at the base of the gutter and connected it to a floating plastic bottle that turned the gutter into a reservoir storing rain water all day then releasing it to make power once it was full it worked most of the time but sometimes the float would get stuck causing the gutter to overflow sending water everywhere it doesn't soak my phone down there but immediately after publishing the video there were about 40 comments telling me i should have tried a bell siphon and i have to say that's an awesome idea but to figure out how they work we have to understand water pressure we've all used a straw to drink from a glass drawing the liquid up and into our mouth we've probably also done the trick where blocking the top of the straw with our finger lets us lift fluid out of the glass in either case atmosphere contacts the surface of the water so we know the pressure there is one atmosphere or one atm but if we could dive into the glass like a swimming pool and swim to the bottom we'd feel pressure increasing the farther down we go that's because pressure is equal to density times gravity times height so the greater the depth or height the greater the pressure but what about inside the straw if pressure increases as we go down then it must decrease as we go up so if the pressure at the surface is one atm then it must be less than that to go up inside the straw so what we think of as suction is simply low pressure or at least lower than atmospheric so when we block the top of the straw we're simply preventing atmosphere from entering and equalizing the pressure drinking from the straw removes the atmosphere pulling the liquid up to drink we can see the effect in these two straws anywhere the air contacts the fluid we know the pressure is atmospheric in the straw on the left we follow the fluid downward and the increased pressure inflates the balloon but for the straw on the right atmosphere contacts the bottom of the straw telling us the pressure inside the straw is below atmospheric that pulls air out of the balloon which is then collapsed by the atmosphere around it now the cool thing about a siphon is it can take advantage of these high and low pressures to move fluid from one place to another without the use of a pump all we need is to momentarily trap the fluid in a vertical tube with the lower end of the tube blocked the only place atmosphere can contact the fluid is in the upper glass therefore maximum pressure is found where our finger blocks the end but as soon as we remove the blockage that maximum pressure suddenly switches to one atmosphere meaning the pressure above it is now lower than atmospheric this easily draws the water up out of the upper glass just as if we were drinking it with a straw this siphon will keep going so long as the bottom of the tube is at a lower height than where the fluid starts and no air enters the tube i honestly wasn't sure this would work but if we clip the tube into both glasses we can keep this siphon going forever just by making the glasses switch places but here's a question if we were to put both the glasses at the same level or even a slightly different level what would happen to the levels of the water and if you think you know the answer stick around until the end of the video and we'll try it and you can see if you're right so now we understand how a regular siphon works but the idea of running outside to suck on a hose every time it rains is not super appealing can we get to the part about the bell siphon already okay okay but to talk about the design of our bell siphon i want to try out this new electronic engineering paper that i got it's really slick it's got to turn on my stylus here we'll start by sketching the roof and then gutter there we go the next thing we need to do is fill in the exit so that we have everything except for our tube and then we've got to kind of fill in the housing of it here and add our uptake tube where the water is going to go in and then fill in between and then add an exit tube right there and of course it wouldn't be a bell siphon without some kind of bell so let's throw that on right there okay i realize this is sort of an unconventional design but it gives us the opportunity to do some cool stuff for instance all we have to do is move this point up and down this sets the height of where the water will begin to exit so it's it's how high it can get without it overflowing the gutter and then if we move this up and down this basically says how low it'll drain down to so it makes it super easy to adjust those two set points if we want to see how it works let's just activate the water here and we're just going to fill it in okay here we go so we're coming up inside the entrance tube and it's working its way up now it's filling up inside the bell but it's still not triggering yet we have to get okay so we're getting up to here and the water can start to flow down the exit tube and we just have to get high enough and get high enough flow to where it starts to trigger oh there it goes it's draining sweet okay so it drains all the way down all the way down all the way down and it's maintaining the suction there like it's supposed to until it gets down to the bottom of this tube and then there we go it loses suction it drains all the way out and it's done and it's ready to start the next cycle and it does all of that automatically which is awesome because then we don't have to go out there and be messing with the gutter all this left to do now is build the darn thing and i love machining but when it comes to light duty parts it's hard to beat going straight from cad to a 3d printer just remove the support material and it's ready for assembly i'm sure my wife won't miss the glass i stole i mean borrowed nice [Laughter] that fits awesome all right let's check this thing out but before we can install anything we've got to tear out the old toilet valve and all the plastic we glued in there fortunately hot glue is no match for a heat gun thanks to careful measurements and a bit of luck things more or less fit like they're supposed to we just need to squirt in some more hot glue to hold it in place for a quick test i'm inflating this plastic bag in the gutter so we can use the hose and not waste a bunch of water and let me say as an engineer when you've been thinking about a design for months and you finally get to test it it's nearly impossible to contain your excitement [Music] [Applause] that is awesome but i think we've got some things we've got to address all right i want to show you something i was worried about this the gutter is full the bell siphon is passing water and it's not doing anything it's not it's not doing its cycle but it's actually gonna start sucking the water down it's just sitting here it's raining water is falling in the gutter but we're just losing it down the belt stipend as if it was just some leak check check this out it's like it needs a certain minimum amount of flow to even trigger the thing we can see down here the water is running down the tube and i mean there it is we're losing we're losing the water and we're not getting any power out of it in fact if we go back to that wiki page and read the fine print under automatic siphons it says the most common failure is for the liquid to dribble out slowly and that reducing the tube size often helps so i'm going to try jamming something in the exit to see what happens okay so the bell siphon is working and right now i've restricted the end of this little tube here so that it will start at a lower flow but now it's flowing at a lower flow as well so where before we were going for that two gallons a minute so take you know roughly 30 seconds to fill this gallon jug i'm at four minutes to fill the thing and that's just not going to work i immediately grabbed my sketch pad and explored a bunch of ideas for solving this with floats and valves until i recalled the kiss principle which stands for keep it simple silly and turns out if i just waited a little longer with the rain the thing was about to cycle on its own oh oh there it goes there it goes there it finally went so it it reached that level that it needed to to actually trigger the auto siphon and now it's going to drain really quickly that was cool to be here for that so with the rains in full force i'm pulling out the restriction to let it run and see what happens okay here we are again bell siphon is not quite triggering we've got plenty of rain but there is this point here where it just sits nice and flush with the top of that tube and water is going down you can see it running down there but it's just not triggering it it needs to be sufficient flow for it to work oh i heard something is it starting oh there it goes that's pretty cool that's pretty cool oh yeah boy that is flowing see if the leds oh just like they're supposed to led sat here all summer and they still work now here's the thing i want to see i think the overflow might be dumping a bunch of water oh it's not look at that we are matching we lucked out the speed of the siphon is just matching the consumption from our jet down there i couldn't have planned that if i tried so we're actually supplying water at the rate oh that is beautiful the the siphon is pulling the water down out of the gutter and supplying it here at this nice just ideal rate it's just filling the tube so we're not wasting any of it down the overflow that is sweet at this point all indications are we've got this thing nailed so i'm setting up cameras on time lapse to record the action on probably the rainiest day this year we caught the bell siphon cycling a good seven times each time adding just a little more charge to my battery i have to say this is working way better than the toilet valve ever did and is far more reliable but just when you think you've got it all figured out this happens ah look at that it's raining so hard it's over my uh over what the scifi can handle i gotta open fortunately i have an overflow on this end let it down all right note to self work out an overflow that should fix it yeah okay and we're charged but wait i almost forgot we've got a siphon experiment to get back to okay it's time to try that experiment to see what happens if we put the glasses at the same level on the same shelf it looks like the water actually equalizes to exactly the same level now what happens if we put one at a slightly different height the water levels out again at exactly the same height not to the level of the glass but so that the top of the water is at the same height and that's because atmospheric pressure is the same in both glasses and we know from fluids that at any point in the system if it's not moving the pressure has to be the same at that same height that's pretty cool that's actually that's really cool but as soon as my son walked in and saw my experiment he literally took it to the next level he added a third glass with another piece of tube at a third height which as you might expect leveled out the same as the first two going further he added water to the third glass which he predicted would eventually equalize with the other two nice work as always if you like my builds and want more of them on the internet like subscribe look for me on patreon and i'll see you in the next video bro

Channel: Quint BUILDs

Views: 5,979,231

Rating: 4.9092116 out of 5

Keywords: Mark Rober, smarter every day, veritasium, bell siphon, siphon, rain power

Id: z-GLzQ2bqEk

Length: 16min 45sec (1005 seconds)

Published: Thu Dec 03 2020