Building a Turbine Car

3 2 1 there's something satisfying about using compressed air as a power source whether it's for powering fullsize bikes radio controlled aircraft or self-destructing helicopters but one area I haven't fully explored is the use of compressed air turbines this video is sponsored by on shape more on them later before building some turbines we need a method of measuring their performance so I'm going to build an inertia dynamometer to do this I bought a steel disc from eBay and drilled a hole in the center which allows it to be mounted to a shoulder bolt that will act as a shaft for it to spin on well more spin with as I glued the shaft to the disc so it can be spun by the turbine then just a few coats of paint to prevent the mild still from rusting before building the test Mount that it will spin on it just needs balancing before being spun up to several thousand RPM which can be done by removing some weight from the heavy aside by drilling some small holes an inoa dno works by attaching a test device in this case a turbine to a heavy fly wheel and accelerating it up to speed and by measuring the acceleration of the wheel we should be able to determine the turbine's torque and power output but first we need to measure the RPM of the wheel I initially chose to use this infrared sensor which outputs a high or low signal as the lines on the disc pass by which is the same way that these commercial tachometers measure RPM the problem with this system is it counts the number of lines that pass by the sensor in a given time period for example how many lines pass by in 1 second and the longer this time period the more accurate the reading now this is fine for measuring a constant RPM of say an electric motor but because we want to measure the acceleration of a turbine we need to be able to measure its speed several times per second and this system just isn't accurate enough also with the wheel being directly driven by the turbine it might be a little dangerous having this thing spinning at potentially 20,000 RPM so I scrapped this design and built another inertia Dyno with a magnetic encoder that gives really accurate angular position and RPM measurements as well as a gear ratio so the turbine can spin much faster whilst keeping the flywheel at a safe speed I then 3D printed a test turbine on my form Labs form 3 resin printer as it's capable of high Precision Parts like these small turbine blades as well as a small diameter nozzle to direct the air through the [Music] turbine this test was run at 60 PSI using a large compressed air tank and the turbine reached a speed of just over 18,000 RPM which using the encoded data can be plotted on a graph like this now the more torque the turbine produces the faster the wheel will accelerate so at low RPM the gradient is steep which indicates high torque and then at higher RPM it starts to flatten out indicating lower torque and we can plot this as a torque versus RPM graph which reveals an almost perfect straight line as the torque reduces whilst the RPM increases which makes sense as the torque produced is a result of the air hitting the blade so as the blades spin faster the speed difference between the air and the blades reduces this might seem like the turbine performs best at low RPM as this is when the max torque is produced but this is when we need to calculate the output power of the turbine which is a result of both the torque and the RPM so by plugging the values into this equation we can plot a power versus RPM graph which gives us far more information on the optimal range for this turbine with a peak output of about 11 Watts at just under 10,000 RPM now this turbine design isn't anything new as I used a similar design when I tried to build a compressed air powerered helicopter a few years ago but from my previous tests it performed really well in terms of thrust produced and also ease of build because it doesn't require any tight tolerances between moving Parts before a while now I've been wanting to try a turbine known as a vein motor this turbine uses a wheel that spins within an offset housing and has a number of freely moving veins around its circumference which which are forced outwards as the turbine spins so as high pressure enters through the top left it pushes on the blades and gradually expands as it travels around the turbine this is the same turbine that's used in many pneumatic tools and it was also used by a fellow YouTuber works by Design where he powered an orop to with one I highly recommend you go check out his video as it's an awesome project but unfortunately I couldn't get mine to work nearly as well I mean it worked but the friction between the parts combined with the lack of airtight seals made it incredibly inefficient I then thought I should test a commercial pneumatic drill as this also uses a vein motor and should be a more perfected design and it sounds [Music] awesome but it does drain my air tank very fast this is at real time speed with a 24 L compressed air tank with the amounted to the inertia Dyno it produces lots of torque at much lower RPM than the 3D printed turbine but this makes sense with the amount of air it's draining so let's compare the efficiency of both turbines by running them off a fixed volume of a 2 L drinks bottle at 80 [Music] psi the 3D printed turbine runs for about 20 seconds and produces a peak power output of 7 Watts with a maximum speed of 8,300 RPM and the pneumatic [Music] drill well it drains the bottle almost instantly I then wanted to try some different blade profiles on the original turbine so I printed a few to test this is the original design with these basic c-shaped blades which will act as the control and at 60 PSI it had a max power output of 11 wat I then printed this design where the trailing edge of the blade is Centric with the radius of the following blade creating a constant width channel for the air to flow through which performs significantly better with a max power of 12 wats but a much higher max speed of 19,400 RPM and finally this turbine design which is similar to an aircraft Wing but it's not a specific air foil profile it was just inspired by these blades I saw whilst researching gas turbines and thought it was worth testing this produced a max power of just under 13 Watts but interestingly it had the same maximum RPM of the second turbine I also reran these tests but instead of the constant 60 PSI from my large air tank I used a 2 L drinks bottle pressurized to 80 psi as this will be the air storage configuration that will be used later in the project and with this test the second turbine performed the best so either the second turbine reaches a higher output power before the pressure in the bottle reduces or it prefers the higher pressure of 80 psi either way the results are very close so I don't think it'll make a huge difference at this stage I also threw in One More Design which popped into my head the other day which has these channels to guide the air down towards the center of the turbine in the hope that it would capture more momentum from the air but with a Max output of just over 4 Watts we'll choose to ignore that design so until I find some more efficient turbine designs to test let's apply this data to something that will produce more than just a high pitch Screech well it might also produce a high pitch Screech I started by printing a chassis that will house the turbine because who wouldn't want a radio controlled turbine car and in order to make it radio controlled I also printed a valve that will act as a throttle where this small tapered piece should vary the air flow to the turbine and with this mounted in the chassis I can attach a Servo to hopefully control it remotely then I attached a small length of tubing to join the throttle to the turbine nozzle that will direct the air into the turbine this turbine design is almost identical to the ones tested earlier but it has a gear to drive the rear wheels only issue is I think I broke this bearing whilst pressing it into the Hub so I'll need to change the design later but at least it mounts in the chassis okay and aligns well with the nozzle I then attach the mount to hold a drinks bottle as the pressure chamber which can be plumbed into the throttle with some flexible tubing as as well as a one-way valve for filling the bottle with compressed air using a bike pump so I've just printed a new turbine uh this time it's printed out of half resin and half pla fdm print uh this way I could press fit the bearing a bit easier and I can also change the gear if I need to at a later date uh and what we can do is press in this little hose which is the same uh connector type as my previous air power plane and pump up the bottle so I've just filled the bottle up to 50 psi uh I can hear a small leak but it's not too bad if I just turn this twist cap pull it out so now the whole system's pressurized and I should be able to throttle up and the turbine should spin who that is so very cool the next step is to add some Wheels which I chose to use these ridiculous looking dragster tires that will hopefully handle the full 11 wats of turbine power with these attached to the rear axle and a gear ratio that should hit max power at around 15 mph the rear end of the car is now complete and it's time to build the front end of the chassis to keep the weight low I decided to use two carbon fiber spars to mount the front chassis and the bottle should sit on top of the spars nicely so once once the front chassis is clamped in position it's time to attach the steering and some slightly smaller Wheels to be honest these wheels would probably have enough grip to be the rear wheels too but those drags the tires weren't cheap so I'm sticking with it then both the front steering pivots can be joined with a steering bar that will create the necessary steering geometry and last but not least some messy Electronics mounting which I'm not proud of but this is a prototype so why make it neat God we got a lot of pumping to do today unplug the hose and see if it drives it doesn't go very far but let's try a high pressure in a straight line [Music] [Applause] that's not coming back what the range of this car isn't great the turbine isn't fully to blame with nearly 34% of the car's total weight being in the rear wheels there's a lot of rotational Mass to accelerate acting almost as an inertia Dyno itself having said that this turbine still has a long way to go before it outperforms the efficiency of my previous air engines but now that I have the inertia dynamometer it will be a lot easier to develop and Test new designs like multi-stage turbines with multiple rotors and stators like full-size industrial gas turbines use or if any of you watching have some turbine ideas to try maybe try hopping into on shape to turn your ideas into 3D models onshape is a professional 3D CAD system that was built entirely in the cloud and works in a web browser which sets it apart from traditional CAD systems as it never crashes and every single action you make is recorded so you can always revert back to changes you made if a design doesn't quite work also being able to collaborate on designs is a very important part of creating a project and on shape allows you to share designs in real time with others or a project can be split into a GitHub inspired method of branching and merging so someone has an idea to make alterations they can create their own branch and work on their idea without disrupting the main design you've probably see me use my formlabs resin printer in many of my videos and formlabs has just announced their new form for printer which was actually fully designed in onshape so if you're an engineer product designer or just want to turn your idea into a part onshape are now offering up to six months of their professional version for free so I highly recommend you go check out on shape at on shape. proo slom Stanton the link will be in the video description thank you very much for watching one last thing I'll be at open source this year in San Francisco between June 14th and 16th last year was an absolutely amazing event and this year is going to be even better with so many YouTube creators and so many exhibits and everyone bringing all their cool inventions and just having a great time so if you haven't got your tickets yet I highly recommend you buy some and I'll hopefully see you in San Francisco very soon thank you very much for watching goodbye

Channel: Tom Stanton

Views: 810,996

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Id: 6gchoHrsCp4

Length: 14min 2sec (842 seconds)

Published: Sat May 25 2024