What is a Coanda Effect Staircase?

the colander effect is the tendency of a fluid jet to stick to a convex surface that's why a ball will balance on a jet of air and stay suspended in the jet of air even if the air is at an angle that's because the air sticks to the surface leaving it constantly suspended in the jet of air tom stanton has demonstrated this really well in his channel and the reason it works is that faster moving air has lower pressure and so atmospheric pressure is higher pressure and that pushes the moving air towards the curved surface you can check out more demos in tom's channel and also check out his colander effect drone and the coanda effect hovercraft although he comments that they're not very efficient in a previous video i made a machine which uses a screw to raise balls out of a sump and throw them out of a chute at the top however you'll notice that the screw isn't actually turning but the machine still works so check out that video to see how that works at the end of that video i commented that i'd like to make more machines that demonstrate engineering concepts and pass balls from one stage to the next this is typically called a great ball contraption most of them are lego but mine are going to be 3d printed so i've decided to try and make a stage of the machine which uses the colander effect to pass the balls along first of all we need to move some air so that we can blow some balls along so i bought some small motors with propellers on from amazon these are four and a half volt motors and i'm powering them actually from a 7.4 volt lipo and they seem to have quite a bit of thrust so i've mounted one in a 3d printed case so i can put it on the ground and air can still be sucked in from the bottom and that will see if it's got enough power to suspend a ping pong ball my intention is to blow the balls uphill and demonstrate the crander effect that way although of course we could just blow them along a curved surface without gaining any height at all but it doesn't look like we've got enough thrust there to do anything at all really and the balls just fall down the next thing to try is a proper edf but i didn't want to go crazy and use a big brushless edf so i found these brushed edfs which are 75 millimeters with a normal dc motor that we can just run off a battery these seem to have quite a bit more thrust even on a 7.4 volt battery even though they're actually 12 volts and if i get it just right i can suspend the ball on a jet of air just like we did with the air compressor demo at the start of the video so that seems much more hopeful but can i lift the ball up and get it to stick to a curved surface well i decided to make a custom 3d print this time which is basically a round hole to stick the edf in and then i'm gonna have a curved surface that comes off the top there's no easy way of printing this without support material really so these prints were quite long because there's a big overhang the finished part resembles something like a big weird shoe horn with a hole in and a flat surface the edf goes into the hole and then we can blow a ping pong ball up and see if it will go up and around the bend well it seems to work about 50 of the time but sometimes the ball needs a little bit of persuasion but this isn't really been aerodynamically designed i just did whatever i thought so i think we can improve efficiency with a slightly different design it's time for version two and in this design i've kept the curve all the way up rather than it flattening out to a flat surface so hopefully this will help channel the air a little bit better thanks to 3d fuel for the filament for this project and lots of other projects so check out my channel for more 3d printing and check out 3dfuel.com let's power this one up and see what happens well that seems to work much better i'm really happy with how well that works in fact it seems to work consistently and every time the ball gets drawn up and gets thrown over the top so i printed some more and we're going to try and make a cascade so one feeds the other like a set of steps to do this i've made an aluminium and 3d printed frame using 2020 extrusion and i've made brackets which use drop in t-nuts and that means i can position the parts anywhere i want and slide them around and move them later and these simply just screw on they're dropping t-nuts so you just place the part and do up the bolt any of the parts can be slid around on the rails and that makes it really easy to configure later and really easy to assemble and disassemble made special brackets for the tubes and the edfs which again fit onto the upright rails and that means i can move them up and down later if i want to i've just stuck those brackets to the tubes with some sticky tape for now so again they can be moved if they really need to before trying to power them all up at once i thought i should see how much current they draw each edf draws nearly 7 amps on a 12 volt battery and around 4 and a half amps on a 7.4 volt battery so we need about 15 to 20 amps of current source to actually power them my 7.4 volt battery is 45 to 90 c and it's 5 amp hour that means we can draw 45 to 90 times 5 at once which is plenty my 12 volt battery is around 12c that means we can draw 12 times 5 amps at once so i'm going to use a 12 volt battery and make a speed controller out of an arduino and a dc brushed motor driver this is a bts 7960 which can do about 40 amps so i've implemented some code that can control the speed and turn the fan on and off [Music] there's quite a bit of thrust in these fans and we can actually see the mounts bending and the plastic bending as we rev the engine so let's throw some balls in and see what happens now i can adjust that fan speed to get it just right but that looks like it's working pretty well with the ball going right up the steps there and sticking to the curved surface so it's demonstrating the clander effect pretty well it's not totally reliable though but it seems to work about eighty percent of the time at least getting two stages up [Music] i was wondering if my hand being there affects it because of course that would cause air to stick to my hand and not be drawn up the staircase so the ball will just shoot straight up i tried different techniques for putting the ball into the bottom edf and it seems to work slightly better if i kind of throw it in just up a bit more thrust there because the battery goes flat while it's running sometimes the balls get stuck but if i just sort of throw them in then they seem to go all the way up and that works pretty reliably as i mentioned the plan is to get balls from each stage and pass them to the next stage to make a great ball contraption so we need some way of reliably getting balls from the last stage and passing them into the edf as it is i don't think it's going to work very well but we can test it as it is and see what happens so it seems like it's time for a new piece of the mechanism this consists of three parts including the chute the top two parts are basically a place where balls fall in from the last stage and then a gate which means that only one can fall through at a time this means we can regulate the flow of balls and we can also make sure that they fall down at the right rate i fitted a motor that turns the gate and that's just the dc motor it's 100 rpm and these are about 10 pounds on ebay however it's a little bit fast on its own which means the balls just bounce back so we're gonna need some sort of speed control but let's put the whole thing together put the chute on and then we can do something about that the third part is the chute which hopefully throws the balls in the same as when i was throwing them in by hand so we can align that on the rails and then we can see if it works i'm using an ibt4 motor driver that you can commonly find on ebay and amazon to drive that motor this one's lower power and i'm just feeding that with a fixed analog right function from the arduino so the motor runs at the right speed we can see now it reliably takes the balls and throws them down the chute i have implemented a little ramp which is the black wedge in there i was hoping that the previous stage would back up enough balls to have enough pressure to push them into the notch but it doesn't unfortunately so i've just added a little wedge to make sure they reliably get fed and that seems to work pretty well so let's give that a test we can see the balls are getting fed reliably at least but sometimes they shoot off at a funny angle the battery's going flat while i'm testing as well so i have to turn the speed up a little bit sometimes there's also some fluctuation in fan speed and that seems to be the edf blades coming loose because the grub screws come undone so they grab and let go of friction on the motor shaft which gives a funny effect as well i decided to move the edfs a bit further apart so each stage has a gap between it and see what difference that makes unfortunately it doesn't really seem to help much though but it's an interesting experiment there's quite a lot of air of course being pushed up those tubes and the balls can float above them so i thought that might work and might give some more space for the updraft from each edf using the 2020 extrusion allows me to easily slide everything around so i'm going to try moving the edfs down so the ball will drop down onto the air coming up and see if that helps well that still seems to be largely the same with the balls shooting off in the air wildly even if i turn the fan up or down it doesn't seem to make any difference so i've put all the edfs back where they were and now i'm going to move the chute closer that's feeding them well it nearly did it but on the whole it's not very reliable at all we need to do several experiments to see what works best so i've just moved the edfs much closer to each other and slightly lower than the next one obviously air will be pushing that ball up anyway well that was slightly better that one was almost perfect i thought the chute probably has the same commander effect as the first tube on the first edf so air is probably getting stuck to that tube as well and blowing the ball right up in the air so now i've moved that shoot away this seems to work a little bit more reliably so i decided to move it further away still and see what effect that has i actually found that i had to turn the fans right down and now it's fairly reliable about 80 of the time i can get the ball to travel all the way up and come to a predictable place at the top if i get it just right then the ball actually hugs all of the steps and that clearly shows the commander effect so the ball actually follows the contour we only lose a couple of balls and the majority of the time it seems to work pretty well that one worked exactly how i thought it should work when i started designing it and that one almost that was almost perfect yep that one was perfect that one almost and it reliably came to the top and that one as well so the feeder seems to work almost as reliably as when i just fed them in by hand at least they come to a reliable place on the top and only one or two get lost so i'm not too unhappy with how this works it does demonstrate the co-andre effect of course you'd normally expect the air from the edfs to just shoot the balls straight up in the air but as it is it follows that curved surface which is just what we wanted to set out to demonstrate there are several improvements we can make though i'm pretty sure the air spinning coming out of these edfs is causing it to do something unpredictable and sometimes throw the balls out to the side so it might be better if we had some sort of vertical vanes that would give us more laminar flow or at least air which isn't spinning and then i thought it would be less noisy and more power efficient if we just had an air compressor with a big tank of air and three hoses with three regulators and then we had air that's all moving in the same direction that'll probably be much quieter and probably still demonstrate the same effect but i'm going to put all the cad and the code on github all of its open source so if you want to build a section of this to demonstrate your own co-andre effect or build anything similar to this you can modify it and all the code for the arduino will be there as well for controlling the fans and the other motor speed if you'd like to support me through patreon or youtube channel membership then those links are in the description to this video patrons and youtube channel members can get access to all the videos up to a week early and sneak peeks and pictures of what's coming up and be part of that discussion alright that's all for now [Music] [Applause] [Music] you

Channel: James Bruton

Views: 281,770

Keywords: coanda effect, tom stanton, tom stanton coanda effect, tom stanton engineering demo, tomstantonengineering, coanda effect demo, coanda effect engineering demo, coanda effect concept, engineering concept, engineering lesson, engineering experiment, science experiment, science lesson, science demo, 3d printed science experiment, 3d printed science lesson

Id: Nfm7YO0PqRU

Length: 15min 53sec (953 seconds)

Published: Tue Jan 19 2021