It moves more air, more efficiently, generating more torque on the prop shaft. The motor simply doesn't have enough torque due to the propeller having more mass and air resistance.
The motor needing to do work isn’t a sign the prop is bad. Moving air takes energy, if the prop moves more air, more energy is needed. Thus motor strain
@@rossmcdonagh1554set to the same RPM yes, but it doesn't mean they're achieving the same rpm. If a different propeller has more drag it's just going to go slower. The only variable that's the exact same is the power of the little plane.
@@j-schnab6338 that wasn't even the point why I suggested it but yes that also comes in handy. I just think it's another good measure to compare the noise level since we don't really car that much about rpm but more about thrust that just happens to be higher at higher rpm.
Its not only the -6 dB that makes it feel quieter, but also the reduced frequency peak and uniform noise spectrum, similar to how they made car tires less noisy.
It's not only the decibels that impact the noise. The toroidsl propeller smoothes out the peaks in frequency of the nornal propeller making it more comfortable to listen to
Yeah, also, you can’t just make a toroidal shape and expect it to be good. There’s a fair amount of engineering involving the pitch and angle attack. The fact that a thrown together experiment matched up to a calculated prop at all is impressive.
sometimes good craftsmanship can overpower poor research. Not saying it's proper, but definitely cool and worth something yeah@@grubalaboocreosote4774
@@MONKEYGUY8504 symmetry has nothing to do with it. It just produces a different sound because it interacts with the air differently than a straight propellor
There is another problem at play! Another guy on RU-vid was putting together his own RC boat, and tried those types of propellers. He found that there’s quite a difference depending on whether they’re FDM printed(like you’ve done here), or Resin Printed. Then again, he was messing with submerged propellers; any residual air could mess with its performance.
must be talking about RCTestflight actually i have the list of RU-vidrs testing such technologys and it's growing with dates for chronological timeline frequency of information spread and advancement 😊 the real bonus is weed free so your small lack in efficiency becomes a heavy improvement on efficiency for heavier weeded areas boating or i guess for planes bird strike strength etc though you aren't trying to tangle with such obstacles
The edges of those propellers looked squared off and blunt while the traditional propeller looked more refined. If you want a more fair test, you need to print your own standard propeller to the same materials and standards as the toroidal. The toroidal propellers I’ve seen were precision milled to extreme precision using a 5 axis CNC to achieve their superior numbers.
@benji3900 simply because that's the only real world scenario that matters if you are focused on the sound alone. The traditional propeller makes alot more thrust, with only slightly more decibels. In the real world situation, where you need the same amount of thrust for these to be equal in performance, the traditional propeller will probably be quieter.
For those who don't know being 5 db quieter is a little more than a third as loud 10^.5 it's because the math for db is logarithmic meaning that every 10 bd is ten times louder or 10^1 20 bd quieter is 100 times quieter or 10^2 and 30 bd quieter is 1000 times quieter or 10^3
You are wrong. Psychoacoustics isn't an exact science because it's so subjective. In general 6-10db difference is considered half or twice as loud but it differs from person to person. Also it's really hard to tell when something is "twice as loud". What you're referencing with 10, 100 and 1000 times higher is the change in effective sound pressure in Pascal. The entire point of the db-scale is to get rid of the logarithmic factor because our ears sensitivity to sound pressure follows a logarithmic scale. And working with pascal directly is impractical. 0db is the hearing threshold of the average human.
@@NiliMotoI was hoping someone commented this. It's also why I personally go by the 6db scale as that's how SPL is measured... and that's all I care about :D
just a reminder to everyone that a difference in 3 decibels is a multiplier of 2, meaning that 6 decibels is a multiplier of 4. Edit: Big thanks to yt for telling me that a whole 2 people liked my comment. It really helped me a lot to know.
I think what people don't immediately realize is that the 5 bladed toroidal prop being 6dB quieter is 4x quieter than the standard prop. That is an incredibly substantial difference.
I think the reason the toroidal propellers have some issues is the weights at the tip as they loop over into the next propeller. You might need to drill holes there to allow some air to fall out through it. If not that, then you might need to change up the shapes at the tips to account for air manipulation.
i think the mass distribution is affecting the moment of inertia and requiring more energy to spin the toroidal one. you may need to print it again with a different design to see better results
Yeah can you can see all the rough around the edges and extrusion which is spoiling airflow, a more refined design like the initial standard prop would be interesting.
@@TowerCrisisI can’t see that if you have a dremel and you spin it and apply lots of friction it won’t spin as fast. Or if you add a lot of weight to it. Now a car with steel wheels and the same car with magnesium wheels will spin the same because of the gears and the tiny amount of total output that’s used to spin them.
It would be interesting to reduce the throttle on the regular propeller to match the thrust of the torodial ones. Then you could compare the noise levels at identical thrust. Also measuring current draw would be informative.
That would indicate a designed inefficiency in fuel and power, which in turn would be better solved by just flying slower or getting better headphones. As for civilian noise complaints, just fly higher.
It's important to note that 6 decibels is actually a big difference. For reference, every 10 decibels is double the volume. This means going from 10 to 20 decibels would result in a 100% increase in noise.
You did not address weight. If a propeller is heavier, it will spin slower given the same torque. That would explain the quieter sound and decreased thrust.
@@goofballbiscuits3647 Top speed is affected way more by drag and not weight, weight is more relevant for acceleration and climb rate. Top speed will only be lowered if drag increases, which may not happen with a small increase in weight.
@@goofballbiscuits3647 Top speed is affected way more by drag and not weight, weight is more relevant for acceleration and climb rate. Top speed will only be lowered if drag increases, which may not happen with a small increase in weight.
@@reinbeers5322 Sure, acceleration is more affected but saying only acceleration is affected it flat out wrong. This isn't a zero-sum gain. Propeller efficiency changes with airspeed. Change the propeller, expect that power band to change. Propeller efficiency can also allow the motor to be over-revved. Propeller length should be determined by the *_motor_*. He did not change that iirc. Only changing the propeller is going to affect more than just acceleration. It will affect the entire passage through the medium. As displacement of air is also critical, not just drag. "Better to move a lot of air, a little."
It's worth noting that the toroidal props were designed for drones, where sound and turbulence can be annoying. The lack of a clearly defined tip makes for less turbulence and thus easier landings.
The toroidal propellors also remove the higher pitch sounds from the propellers, which makes us percieve them as being even quieter even without a huge change in decibel level.
How thin can you print without compromising rigidity? Lessening the mass of the blades and moving the center of gravity to the fulcrum would be the best strategy to both increase inertia and lessen drag.
The reason the 5 propeller was quieter is because the more propeller blades you have the less it needs to pull the air to move which makes it create less noise
Run the regular propeller at lower speed to produce the same thrust, and compare the noise. I guess that regular will be on par with the newer ones. If they are spinning slower and producing less thrust then of course they will be quieter.
Important thing missing from the thrust measurement is a simultaneous measure of power being drawn. The toroidal props could be weaker but drawing less power making them more efficient or weaker and drawing more power making them even worse. It would be interesting to see this measured together for a more complete picture.
I’d imagine the mass, especially at the tips is MUCH higher so the lower thrust and sound is probably due to a lower RPM, and power draw would likely be higher
Im trying to understand this comment. The motor should be drawing a fairly constant amount of power regardless of what its driving. The lowered performance would be some summation of the properties of the printed propeller making it harder for the motor to apply torque to. I think to make this test "fair", one should iterating the design of the toroidal propeller itself. By that i mean, the printed propellers seem suboptimal compared to the original design. My intuition tells me if he played with the mass, cross section, raidus and/or print material he'd see better results. Essentially he needs to lower the Mass moment of inertia to make the propeller easier to spin, then he can start playing woth thrust properties.
@@h34dshotgl0re By power you mean amps, right? I don’t know a ton about how to calculate amps from prop mass/pitch/size, but I do know a bit about power consumption in general. A motor has a KV rating which for our purposes is the number of RPMs the motor will spin at a specific voltage. The amount of current the motor is going to need to do that is going to change based on the load. So no prop requires few amps, big prop requires big amps OR big prop pitch (more air pushed per rotation) also requires big amps. So you’re completely right, they need to test different prop geometries to actually see if they can optimize the design to be competitive. I just don’t think it’s going to be useful to try to compare a homemade design to something designed by the pros, then claim conclusions based on an amateur attempt :(
Important to understand: this is not about "toroidal vs regular", but _these random DYI 3D-printed_ vs _factory-grade molded optimized for this motor_ .
I like this type of videos, let's make them normal. No clickbait, strait to the point well filmed with captions so i can watch it while my baby daughter goes to sleep. Nice
You need to account for the weight differences and drag too...causing the motor to turn slower RPM, hence quieter and less thrust. Match RPM and then test.
the thing with decibels is that they get kinda exponential like 10 points is nearly 10x louder or some shit so 6 decibels quieter is like 5x as quiet or something
3dB is about the smallest sound level change you can discern The sound ENERGY doubles or halves with a 3dB change, but eyes and ears have logarithmic intensity responses, not linear
@@definingslawek4731 if you 3d printed a normal one it probably wouldn't fare well. That rough surface will have a high Renoylds number and be generating a lot of noise/drag I'd be highly tempted to 3d print blades using my SLA printer rather than relying on any kind of extruder. This can produce a surface which is almost perfect (and flexible with resin tuning, I've done this for "clothespeg" type electronics clips otherwise they snap after a couple of uses) and can be further improved with acetone treatment before final hardening
Nice test! I think you should also 3D print the regular propeller from the same material you made the toroidal propellers, perhaps the finish has an effect on the final results.
As far as I've read, these propellers are more efficient in a specific range on rpm, but generally less efficient than regular propellers. Also, they were initially designed for marine use.
As far as the "quieter" thing, you have to look into apparent volume by looking at the waveform average and seeing which frequencies are low and high. The pitch of a sound can make it seem louder or quieter.
The two biggest factors of a propellers efficiency is the angle of attack and the diameter. Two blade propellers are typically more efficient as well, but louder.
I would add that the distance away probably affects the perceived volume. The toroidal is probably designed to cut a specific bandwidth rather than raw output, so that it does faster over distance. You might get more measurable dropoff if you don't measure directly under it
If I remember correctly toroidal propellers are supposed to be more efficient, not necessarily more powerful. They are more like a side step to traditional propellers than an upgrade. A more accurate way to rate them would be to record audio from farther away and record how long battery life’s last.
Another consideration is while a lot of the same rules apply, hydrodynamics where most toroidal props are designed from is executed differently than aerodynamics. The blades are usually angled to different amounts. It could be something you already considered, but if not, the difference might matter
Ive found bigger differences comparing quality props to cheap ones. On a DIY drone I once gained 10% thrust switching from generic to DJI props. The generic ones were still quality injection molded and engineered using a time-proven design.
If you match the thrust the sound goes back to normal. They aren't quieter. They just have their noise more spread out over more frequencies that are less audible to humans, there quieter. Somewhat like the tread on tires going from blocky to variable spacing and angular shapes to spread out the impact and therefore spread out the noise.
I think the next test would be could you put in on an engine with higher rpm potential and see how the propeller does as the tips approach the speed of sound (which is the limiting factor for all normal propellers)
There’s a reason why planes don’t use propellers like the ones you’re designing because there’s more air resistance on it, but yeah, it will be quieter because it doesn’t move as fast.
As a person trained in basic aerodynamics and with real aircraft maintenance experience I can say that propellers are specically formed in a way to get as much "bite" on the air as possible as pulls t the plane through the air while minimizing drag. It seems that the new propellers have a lower pull and higher parasitic drag coiefficients. Still an interesting idea though.
You need to 3d print a standard propellor for this to be a fair test. The weight and surface of a printer will never be the same. I still expect the standard twin blade to win. Also, we should remember that because of the geometry of toroidal propellors, it is not perfectly accurate to describe them as "3-bladed" or "5-bladed." A better terminology could be "3-fold rotational symmetry" or "5-fold rotational symmetry." These blades have more like 6 blades and 8-10 blades worth of surface area respectively.
You should compare the motor current as well. Efficiency is also very important thing. I believe that flower-type propellers were rotating slower, so this is why they were less noise and less throsty.
6dB doesnt sound like a huge reduction, but it's a logarithmic scale. Every 3db is effectively double the air pressure. Air pressure and percieved volume dont line up exactly but this is still almost 1/3 quieter.
It looks like the regular propeller is made from a different material than the propellers. I would recommend printing a regular propeller with the same material, to test the toroidal prints against. This will ensure consistency in your testing
The more arms on a propeller makes it grip the air more, so it’s better for maneuverability but it also takes more torque to spin hence the lower power, also more torque = more battery used
To be fair, you should 3D print a standard propeller with the same print parameters as you used for the toroidal propellers which look pretty square on the edges.
I know dude it’s really hard to perfect the shape of toroidal propeller, and also the little grooves that are formed when 3-D printing can catastrophically affect the thrust
The 3d printed propellers might just be a lot heavier than the originals. Plus, while adding more propellers does increase the amount of thrust, it amount it increases by decreases as you add more blades
Very counter-intuitive, as the testing of marine toroidal props saw a marked decrease in cavitation, meaning they were more efficient, which would lead me to think they would be more effective.
Like others are saying it’s stressing your plane cuz it’s too big or too heavy, or if you use a smaller one it’s too small or too light, gotta Have the right specifications
Don't forget that the decibel scale represents a doubling every three decibels because it's logarithmic so the five blade toroidal was a factor of four quieter than the standard propeller. I suspect that some of this absence of noise correlates with an absence of thrust created
Adjust the pitch of your toroidal, and tune for the desired thrust. Think of a constant speed prop - you need “Fine” pitch for take off, and once airborne you back off the pitch for cruising speed. As your little toy doesn’t have adjustable pitch, you have to set it up on the ground.
The famous ultra-expensive toroidal propellers that made all those claims were designed for racing speedboats. You can imagine those being much quieter than the traditional option, but the design just doesn't seem to work great for the air, or it requires simulating the design to get it right for a certain use case, or the use case needs to be specifically very high speed, or it's the imperfections of 3D printing that are nullifying any possible advantage.
I think theres a certain formula you have to use to get the right shape in order to actually get them to work properly. But im sure when made perfectly they are better than regular propellers
It is quite obvious that they are quieter iom that "drag" at the end of the propeller blade does not occur with a Torodial propeller. The question is how much less energy Torodial propellers draw (number of AMP's in the motor) compared to a normal propeller. and that saving can be used to use a torodial propeller with a little more pitch and get more thrust and you go plus or minus zero when it comes to energy consumption.
I think for a more fair comparison you should also 3D print the regular propeller. That way you'll know if the material itself has any impact on the performance.
