Toroidal Propeller Testing on my Electric Surfboard

this video is sponsored by fume more on them later last summer I made a video about testing toal propellers on my electric boat and they turned out to be pretty inefficient this doesn't necessarily mean that toal propellers in general are bad but instead it just means that this specific toal propeller design is bad I took what I learned from that experiment and used it to design what I thought would be an improved version but that also performed very poorly compared to a traditional propeller after all those fails I was extra surprised when I tested out a third toal propeller Design This Time on my V8 powered paddle board and it resulted in a higher top speed than a standard propeller with the same diameter finally it seemed that one of my toal propellers actually showed signs of superior performance I was so blown away by this that I decided to convert my V8 paddle board to Electric this would allow me to collect precise power consumption data and scientifically compare different propeller designs so that's what this video is about let's get started on the electric conversion after giving the V8 one last run I took it off the board and and started designing a mount that would allow me to attach an electric skateboard motor directly to the vertical shaft that comes out of the Stern Drive Unit I'm using this little coupler to adapt the 8 mm drive shaft to the 10 mm motor shaft this is the motor mounting block and it got attached with a bunch of M3 thread forming screws here's the motor going on it's one of the two Motors that I had used on my 50 mph snowcat the aluminum motor mount then got screwed onto the motor mounting block and with that the stern drive unit was converted to Electric so much simpler than the V8 I added an rup pilot flight controller so that I could log the power and GPS speed to be used for measuring the efficiency here's the maiden voyage with the new motor and I'm starting off with the same large B series propeller that I was using in the V8 video if there's one thing that puts a smile on my face it's riding on a new craft for the first time it's just such a great feeling that was not even very much throttle okay let's go pull throttle for this test I had the ESC set to max out at 100 phase amps which is way too much for this motor it would get really hot really fast so I wouldn't have been able to sustain this speed for very long before the motor drive went into thermal foldback this thing is rad no no no don't do that don't do that this thing is not attached to the baddle board well enough it was definitely faster than the V8 and this is even just running on a 6S battery I could run it on 12s and get even faster after trying it out with the Big B series propeller I switched over to the toroidal propeller with this I was still able to go decently fast but not quite as fast as before after that maiden voyage it was time to start the science back when I was testing different propellers with the V8 engine I had intended to make a tootal propeller and a regular propeller that were the same diameter for a relatively fair comparison however I later realized that I had somehow screwed up the scaling at some point in the modeling process and it turned out that the regular propeller was actually 9 mm smaller than the toal propeller so that's probably the Smoking Gun as to why it was outperformed by the thidal propeller but we won't know for sure until we get some cold hard data for this next round of testing I made three new propellers that each have the exact same 6-in diameter as the toal propeller each one has a different pitch ratio so we can find out which is optimal for the RPM and speed that we'll be operating at to make these propellers I'm using this free online B series prop generator more specifically the geometry tool if you enter in a few settings it spits out a nice clean B series propeller after that I loaded the 3D model into on shape and then made this thing here which is basically just a digital mold having that allowed me to quickly and easily do a Boolean subtraction from each of the three flavors of B series propeller that would create all the features which would allow me to print these propellers and mount them on the paddle board shaft if you want to access any of these models yourself you're in luck thanks to on shape and their cloud-based CAD program the native files are just a click away visit the link in the description and sign up for a free onshape account to download copy or edit these files yourself next up I printed all of these propellers out of gray Pro resin on the form 3 plus this resin is great for propellers because it's strong and durable but it still holds its original shape over time after some postprocessing the propellers could be installed onto the shaft and fixed in place with an M3 screw with that it was time to head to the lake for the first efficiency test so I have the vesque set to do a maximum of 35 phase amps so that way I'll just turn up the throttle to full blast and it'll be pulling 35 amps for each propeller and that way we'll be able to do a solid comparison my idea was that I would use a fresh battery for each propeller so that the voltage was the same for each test run if the voltage is the same that would make the current proportional to the power and the power is the metric we need to be looking at to measure the efficiency or so I thought turns out I was wrong I'll explain why later so I did six laps each with a different propeller following the same course I thought we were controlling for power which would make our speed the dependent variable in this experiment so just to recap these are our six contestants we have the big B series propeller the toal propeller and the smaller B series propeller it's 9 mm smaller than all of these and then over here we have the three B series propellers of different pitch angles that are the same diameter as the teral propeller sorry that's so confusing man what a great invention everyone needs a powered ble board this is great here's what our speed data looks like throughout the course of the test runs and we can find the average speed of each run to get our final results turns out the teral propeller won OMG this amazing new technology is going to save us all not so fast turns out I did this all wrong I thought that if I kept the battery voltage consistent then the motor would be putting the same amount of power into each propeller and thus we'd have a fair comparison this all would be true if the motor driver were controlling the battery current but it's not instead it's controlling the phase current battery current is measured here whereas phase current is measured here that's the difference so long story short each one of our propellers were not consuming the same amount of power the thidal propeller was likely getting much more power delivered to it than the lowest performer I'll explain why this is towards the end of the video since if I do it now half of you will probably leave but anyways let's now run a proper test ladies and gentlemen I'm here to talk to you today about bad habits like wasting hours testing propellers the wrong way bad habits can seem like they're impossible to break but what if I told you the best way to break a bad habit isn't to quit cold turkey but instead just remove the bad from your Habit in steps fume the sponsor of today's video fume is an award-winning flavored air device that does just that instead of electronics fume is all natural instead of vapors fume just uses a blast of flavored Air instead of harmful chemicals fume uses all natural flavors that are delicious it's not just the flavors that get me all riled up it's also the Aesthetics I mean just look at this thing the machined stainless steel mouthpiece the lathe turned Maple Barrel the cast detent rosette pattern for precision airf flow control it's just a work of art by golly it's gorgeous I find this thing as fantastic to fondle 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connected with these new settings I headed back to the lake for another round of propeller testing on this day the water ended up being too choppy a rogue Splash hit something critical and my motor stopped working so I had to paddle all the way back the next day I tried again and everything went smoothly I was also in a more protected Bay so there was likely even less influence from any slight breeze that might have been present here are the results this time the 6-in high pitch B series propeller performed the best with the Big B series propeller coming in right behind it turns out the Thal propeller was not the most efficient after all this is what I had expected to find because this thidal propeller is actually just a shrunken down version of this propeller and with L less angle of attack at the tip and that propeller performed very poorly speaking of tip angle of attack what is this it looks like there was a seventh contestant there was indeed so back in my original toal propeller testing video I was talking about how Shero Marines patent shows that their propellers have a positive angle of attack at the tip of the pidal loop this effectively pulls the surrounding water in from the sides which they say increases efficiency this all makes sense but I got confused when I was looking at pictures of their propellers and I could swear that the tips had a negative angle of attack not a positive angle of attack like the patent talks about gasp what if they made their patent backwards to throw off copycats OMG I just had to test it so I went into on shape and made a version of the toal propeller where everything was identical except that it had a negative angle of attack at the tip and after that I printed it and tested it along with the other propellers and it performed the worst out of them all so maybe Shero isn't trying to dup us I still have no idea why it totally looks like the propellers have a negative angle of attack of the tip maybe it's just an optical illusion who knows so we've done our efficiency test but what's the point of knowing which propeller is best if we don't use it today I'm going to do an endurance test to see how much range this thing has I've got the smaller high pitch B series propeller on the back since that seems to give me the most efficiency and I've got a 25 amp hour 24v lf4 battery here and a 10 a hour six cell lipo as a backup I also put a steering servo on the back so that I can control steering with my radio here do that pretty slick hopefully we can run a autonomous Mission with the GPS in the RDU pilot on there I was running Mission Planner on this old Android phone that made it kind of difficult to change settings on the autopilot for that reason I was unable to get it to run the Waypoint Mission I had uploaded so I had to steer it manually but oh well not a big deal on my journey I tried to drive at different speeds so that I could see how speed affects the efficiency once I analyze the data later on oh by the way after posting my previous toal propeller testing video I was amazed at how many people out there seem to be interested in propeller design that gave me the idea to host a propeller design competition where viewers can send in their propeller designs and I'll 3D print them and test them to find a winner if you're interested follow RC testflight uncore on Instagram that's where I'll be posting updates and instructions on how to enter anyways I ended up calling it quits at 7 Miles because it was kind of cold on this day but the battery wasn't even close to empty so now I've got the battery charging I'm using this power meter to measure the wat hours that the battery absorbs and this is the same charger that I used to charge the battery before the mission so it should charge it up to exactly the same voltage and we'll be able to see exactly how many wat hours of power we consumed throughout that Voyage this thing just finished charging it says 13.9 amp hours and 385 wat hours so 385 wat hours and 11.3 km averages out to be 34 wat hours per kilometer that's our efficiency over the voyage this battery has 640 W hours so I only used 60% of its capacity that means I could have gone 18.7 km or 11.6 Mi if I hadn't gotten too cold and bored this power Queen 25.6v 100 amp hour battery that I used to for my boat has 2560 W hours so if I strapped that onto the paddle board I could go 75 km or 46 Mi assuming I was going at the same speed it would take me 9.5 hours to go that far I used a program called MAV Explorer to analyze the rilot log data and that shows us our instantaneous efficiency at different points in the voyage with that data I was able to check the efficiency at different speeds and here's what we get it's very efficient at low speeds and gets much worse as we go faster and faster if I took my speed all the way down to 0.8 m/s with the 2500w hour battery then I could go 427 km or 265 Mi a journey that long would take 6 days days of driving non-stop don't get excited I'm not doing that after the endurance test I switched over to a lipo battery that could handle higher discharge currents for some Full Throttle testing I still had the heavy lithium iron phosphate battery on board and I didn't have the phase current turned up as high as I did during the first ever test to this motor so I probably wasn't going as fast as I was then but I was still able to get up to 3.2 m/s or a little over 7 mph not bad that's barely fast enough to get a speeding ticket in the no a Zone next I hopped off and tried driving it via RC without me on it okay let's go Full Throttle it's so fast oh my god oh that's hilarious how much weight can you put in there and get power just [Applause] [Music] me with nobody on board it got up to 18 kmph or 11.2 mph so that's fun who would have thought that paddle boards make such great RC boats so now I want to go back and talk a little bit more about my propeller comparison testing it's worth noting that the efficiency test I did does not tell us which one of these propellers is more efficient in general it only tells us which one of these propellers is more efficient when paired with this specific motor and while operating at this specific power level and speed it's not impossible that a different propeller could end up winning if I reran this test at say 2,000 Watts instead of 200 Watts but from a practicality perspective 200 watts is pretty representative of the power levels I'd normally be using on this paddle board so for all I care the 6-in high-pitch B series propeller is the best for most everything I'm going to be doing with it now generally if you take the motor specs out of the equation a bigger propeller should always be more efficient than a smaller one of the same design but in this case our bigger propeller was simply too big for this motor so how can this be well the thing to understand here is with electric motors torque is proportional to phase current and RPM or speed is proportional to voltage in order for the motor to run this big propeller at our maximum power limit of 200 Watts it's going to require more torque and less RPM than the smaller propellers or in other words more current and less voltage so even though this big propeller is being fed the same amount of power as the smaller propellers it's it's pulling more current and more current means more resistive losses in the wires and the motor so the motor itself is actually operating less efficiently with the big propeller pretty interesting after my initial attempt at measuring the efficiency of all these propellers I had said that my test was useless because the ESC was set up to control phase current instead of power so why is this if I had set up the ESC to control battery current instead of phase current this test would have been a bit more acceptable each prop would have been drawing the same amount of power out of the battery and it would have been a more fair comparison since the battery voltage was consistent for each test however since the ESC was controlling for phase current instead the smaller props that had less rotational resistance in the water were actually getting more electrical power delivered to them than the bigger props this is because the phase voltage or duty cycle is proportional to the RPM and since the RPM was higher for these props the phase voltage was higher so higher phase voltage time constant phase current equals higher power so that explains why we got higher speeds with the propellers that had had less rotational resistance they were causing more energy to be sucked out of the battery than the larger props so this test was totally useless my test with controlled battery Watts was much more useful it turns out this is pretty much the same reason why the tootal propeller might have done better on the gasoline powered V8 engine it had less rotational resistance in the water which leads to higher RPM higher RPM means more combustion cycles per second which means more gasoline which means more power it's really cool how the same concept can be applied to both gas and electric motors here the fact that the props with less resistance were pulling more power might also indicate that all of these propellers may be a bit too big for this motor if the goal is to maximize power that is big thanks to Oscar from odrive for helping me out with all the technical motor stuff in this video I sure did learn a lot that's all for now thanks for watching bye

Channel: rctestflight

Views: 227,442

Keywords: toroidal propeller, boat propeller, propeller, efficiency, design

Id: oXgp7IGnvKA

Length: 16min 49sec (1009 seconds)

Published: Wed Dec 06 2023