Driving a 7000W Generator With a 500W Turbine? - Wind Power on a CAR #3

the power of the wind is amazing just a moderate increase in speed can double the power output but the wind seldom does what we want so i'm experimenting with wind that we can control the wind in front of my truck the equation for wind power predicts an exponential increase with velocity at highway speeds our 1.2 meter turbine should get over 10 000 watts of wind but something called the bets limit explored in an earlier video limits us to just 59 percent of the available power that still leaves us with around 6 000 watts i've spent much of my summer testing cheap wind turbines rated for just hundreds of watts and none of them measured up but to really check this math we're going to need something bigger much bigger oh my word this thing is huge i was picturing something about a third of that size by the picture online but uh wow okay let's hook it up now we might be tempted to connect a turbine directly to the end of the generator shaft but the bearings inside are designed mostly for radial loading which basically means from the side but wind turbines in addition to spinning they're also taking a lot of thrust load in the direction of the wind basically you can picture it as if it was just a big round disk that the wind could push on and that kind of loading could really shorten the life of the bearings inside of our generator so we're going to design a custom hub with tapered roller bearings which can handle loads in any direction the first step is machining the housing that will hold the outer bearing race and mount to the truck of course we also want a rubber seal in there so the bearing grease doesn't come out and get blown all over the place we also need to attach it to a piece of square tubing normally we'd make a curved cut with a fish mouth cutter but i don't have one of those so i'm using a cnc mill to give it a nice fit next we'll start machining the shaft we don't want any wobble so we're being very careful how we do it supporting at each end helps but even then it starts cutting on one side which tells us how imperfect the material is to start with but eventually it trues up just fine we also need threads to hold everything together and adjust bearing clearance cutting threads on a manual lathe is nerve-racking and easy to mess up but these actually came out really nice of course we'll need nuts to fit those threads so we're making them out of a piece of bar stock left over from another project that's a huge advantage of doing your own build you get to design parts based on the materials you have available the inside thread of the nut is made just like the one on the shaft one pass at a time with a boring bar until the mating thread goes right in smoothly after one more pass on the outside it's time to head to the mill the fourth axis is really handy for making the hex shape of the nut once done it's back to the lathe to split off a piece to act as the lock nut so we can eventually tighten the two together we're eventually going to need some way to adjust the height of this thing so i'm grabbing an extra piece of square tube before welding it all together i know the welds will distort the nice machined hub but there's not much i can do about it without a second machining step and ultimately i don't think it will be all that bad once it's had a chance to cool we can finally try assembling everything to see if it all worked out check it out this is the first taper roller bearing setup i've ever designed certainly ever built and it actually looks like it went together pretty well and of course now i have these two nuts on the back that i can use to cinch up the bearings to exactly the amount of play that i want and then use that lock nut to lock the sucker down so uh man that should hold up to anything we're gonna do to it with the wind all right on to the next part the generator is really heavy so we need a substantial amount to secure it while driving down the road i can't seem to find the bolt hole locations anywhere online so i'm having to settle for taking measurements and approximating the best i can for the two front mounting holes i'm drilling them in the mill but for holes between welded parts i like to wait until all the welds are done before doing any machining i seldom get to do much welding anymore so this is a great opportunity to brush up my skills before going any further i want to check the fit of the generator which looks like it worked out great one last thing i need to do is weld on some nuts for adjusting belt tension and will be ready to check out the final assembly wow i think there's a time for every engineer that designs something and it's easy to use the math and the spec sheet and just pick what you need but as soon as it starts showing up things start getting real that's what's happening with this this is uh this is impressive but i want to take this opportunity to talk about pulleys and gear ratios because from the comment section on the rain gutter series it's clear to me there's a lot of people out there that have a misunderstanding of what pulleys and ratios are for so if you look at this we have this huge pulley up on top versus the one that's on the generator and it's actually exactly three times the size or as three times the number of teeth as the one on the bottom and what that means of course is as we rotate the turbine shaft for one rotation you can watch the generator shaft go through one two and exactly three rotations so whatever speed the turbine shaft is rotating at the generator shaft is going to rotate three times that speed but let's imagine for a minute that the pulley on top isn't any bigger than the one on the bottom let's say they're exactly the same size then the turbine shaft would be rotating at exactly the same speed as the generator and we'd have a one to one ratio but regardless of what ratio we have let's say we took this thing out mounted it to the truck and we start driving around and we're not getting the power output that we think we should it might be natural to think hey well if we just increase the size of the pulley on the turbine shaft then that'll make the generator turn even faster and we'll get more power that way but that's not correct and i want to dive into it right now and show you why the job of the belt is to transmit the same tension force across both pulleys now if we picture each pulley as a lever which one would be the bigger lever the bigger pulley of course well leverage is just another word for torque and torque is equal to force times distance which in this case is the force of tension in the belt times the radius of the pulley since the lever of the big pulley is three times the lever of the small one then we can say it has three times the torque and you can feel the difference when you try to turn the shafts by hand this large pulley makes the upper shaft difficult to turn while the lower one feels super easy and that's because we're turning it directly at a lower rpm which takes less torque to see how change in the ratio doesn't affect power let's say the wind turbine can produce a torque value of 9 at a rotational speed of 100 and just forget about the units for now since the formula for power equals torque times rpm we could multiply 9 times 100 and get 900 let's call them watts but that's just the turbine shaft if our pulleys were the same size we'd have a one to one ratio and we'd be spinning our generator with 900 watts of power but now let's see what putting this giant pulley on the turbine shaft would do like we said at the beginning the generator will spin at three times the speed of the turbine but what about our torque well the lever on the smaller pulley is one-third the size of the big one so we have to divide the torque by three now watch what happens when we multiply to get the power 900 watts hey it's exactly the same and that's what i said at the beginning pulleys and gears don't add any power so why do we even bother with this giant pulley up here well this generator is designed to run at 3600 rpm and this turbine is not now honestly i don't know what speed this thing is designed to run at but i want to keep it and any future turbines at around a thousand rpm and this three to one ratio will do that now i am just dying to get this thing out on the truck for a test drive but first we need to change out some of the electronics the turbines we've tested so far were all three-phase ac which required a bunch of extra junk just to get to dc then back to ac but we're ditching all of that our new generator is single phase so we can connect it right to a heating element using a variable transformer i'm trying a water heater element since i had one lying around and building the mount would allow me to try out my new press brake also milling threads on a machine that was made in the 60s always makes me smile it would have been impossible back then without a computer to follow a helical path all right we're going to test out this heating element and see it's a 220 heating element i've only got 110 plugged into the variac but i want to see if this display is supposed to come on at 80 volts ac let's see if that's actually the case before we have to go do this on the road with the with the truck so here we're turning on the variac okay so 30 doesn't work just came on 35 volts sweet that's way better than uh than the specs the variac variable transformer is 2000 watt it says max 20 amps so let's see if that's the case 700 watts there's a thousand watts right there and oh yeah you can feel that you feel the heat coming off of that heating element awesome that should be good enough to go uh to go try this on the truck oh is that thing glowing it's actually glowing [Laughter] wow look at that that thing is glowing red yeah it's a water heating element it's supposed to be immersed in water um so we're going to go ahead and shut it down but this should be good enough for our test okay here we are we have our new 7200 watt generator connected to our five blade supposedly rated for 500 watt wind turbine and we were only getting a couple hundred watts previously not even that but we're going to find out was that limit this turbine or was it the actual generator itself i'm not optimistic about this flimsy plastic thing the amount of torque that this thing has to deliver from the wind to be able to drive this generator at any decent rpm i think is beyond what this plastic is going to be able to hold up to but we're going to give it a shot and find out we'll start out with no load on it at all and see what kind of rotation we can get if if any and then and go from there what do you think is it how fast are we gonna have to go for it to spin come on sucker rotate that's not even turning there we go finally not quite 35 volts yet whoa what the speed yeah yeah 500 rpm wow so that's nice we're getting we got 500 rpm just by going 40 miles an hour so so it's actually capable of spinning it that's awesome now that we got it going go ahead and turn on the variac let's give this thing a shot and then start turning it up and and go to you know go to like 35 get to that 35 volts so you can get that display to come on oh wow we're almost up at 1000 rpm hey oh i went and slowed down sorry go ahead give it give it a little more give it 40 or something well i guess go ahead crank it a little higher then i'll turn it up turn it up higher how high is it right now oh really it's still turned on right yeah that's weird all the way up okay we'll turn it back down man we'll figure out what's going on because it was working and now it's not so i wonder what we did okay we were getting some initial spinning on this thing and now it doesn't want to rotate anymore i thought maybe there was something wrong with the generator but it turns out that i probably didn't have the adjustment nut cinch down tight enough on my tapered roller bearings and now even with the belt off the thing does not want to spin hardly at all and i didn't bring the tools necessary to adjust it so we're going to head back to the shop real quick and we'll get this adjusted and come back out and give this another shot but once we got back to the shop i realized we don't actually have the right wrenches to fit those nuts but we do have the means to make them i thought about running the mill manually but in this case modeling them up in cad and making a tool path in cam will only take a little bit longer and give a way better result now we can really torque things down so they don't give us any more trouble back to testing 291 96 326 when i turned it on nice 325 378 that's the highest we've had ever nice okay so 378 watts is awesome because it's more than double what we've ever gotten before but it's still a fraction of what the math says we should get now why is that well we can't generate more energy than is available in the first place but we also can't produce more than the weakest link in the chain and that weakest link right now is this turbine number one it's not optimized for the wind speed we're using it at number two take a look at it in slow motion normally the blades flex slightly towards the wind but under load it's getting pushed back behind the plane of rotation sure industrial wind turbines do this too but they're designed for it while this one is not some have suggested the turbine is sitting in a cushion of air being pushed by the truck but our instruments say that's not the case before the turbine starts to spin the wind speed is pretty close to the speed of the truck once the turbine gets going the wind speed behind it slows way down telling us it's doing its job taking momentum from the wind now when i dive in deep to a topic like belt drives a lot of viewers just leave because they came for entertainment not education they're so used to the sugar they don't want any substance and it's no secret the videos with the highest views have almost no educational content no now that leaves creators like me looking for other ways to support my efforts and that's where patreon comes in now this series on wind power is my most expensive yet and so far the ad revenue is not enough to cover the cost of materials and that's where patrons can step in and help offset those costs when a video doesn't go viral now if you're the kind of person who prefers substance over sugar consider heading over to patreon.com forward slash quintbuilds to become a patron there's no minimum contribution amount and every bit helps and if you really want to dive deep i have a second channel build 2 where i post real engineering content there's a series called wisdom from an engineer where i talk about working in teams and handling mistakes there's also the most helpful math trick i ever learned and use most frequently as an engineer i'm even making a video with real torque and power calculations for those that want to see it so be sure to check that out if the links aren't showing up here on your screen check out the video description but everyone likes a little dessert after a meal so at the end of every video i usually put an outtake or something silly as an incentive to watch to the end kind of like movies do at the end of the credits so stick around for that now the next thing we're going to do is what many would consider the black magic of wind power we're going to learn how to design and build our own custom turbine blades but fortunately a number of you have reached out and told me about software that we can use to optimize the blade design but i'm actually looking forward to it because remember build stands for better understanding involves learning and doing so we are going to get a way better understanding of how turbine blades work and what they do we're also going to find out why we left a hole through the shaft of the wind turbine and here's a hint it's for an actuator but that's all for now i'm quint with another one of my builds thanks so much for watching but the wind seldom does what we want so i'm experimenting with

Channel: Quint BUILDs

Views: 1,411,261

Rating: 4.8901129 out of 5

Keywords: mark rober, smarter every day, veritasium, wind, torque

Id: U7ZgG9p-Hz4

Length: 20min 13sec (1213 seconds)

Published: Fri Oct 16 2020

Reddit Comments

[u/PortJMS]

If you watch the video, it isn't about using the car to produce electricity. It is about the generator, gears, etc on how they are used to harness wind energy.

[u/InfamousBLT]

ITT: Everyone who didn't actually watch the video.

He isn't trying to harness energy from the car, he's turning a car into a wind tunnel for science.

[u/TrueBuckeye]

The educational value of this is possibly good, but I can't get over the stupidity of the safety hazard.

1 - mounting that fan/generator in front of the truck is certainly a hazard in a collision.

2 - mounting the exposed heating element RIGHT IN FRONT OF THE PASSENGER SEAT where his kid sits? Are you kidding me?

[u/elitemouse]

Can we talk about how ridiculously dangerous this shit is to just be driving around on public roads?

[u/TheLastSparten]

If you want to generate electricity by driving the car, why would you do it with a turbine strapped to the front? I mean, your car already has an alternator hooked up to the motor to recharge the battery, but if that isn't enough, no reason you can't also hook up a bigger generator somewhere along the drivetrain rather than trying to harvest wind energy from in front of the car.

[u/[deleted]]

I feel like this should be on WCGW