Don't know if it's just me but waiting for the next video to be released is like waiting for the next episode of your favourite Tv show. I don't know why people haven't done this on RUclips before. Keep it up.
I really appreciate your intellectual reviews of all this. I do have some "conceptual" questions regarding the cost/benefits of CR prop systems. 1. The relative air velocity over the airfoil of the prop is what develops thrust. Thrust can be increased by either increasing relative air velocity (increase RPM) or increasing pitch of the prop. Both of these require additional power input, however increasing RPM has a squared component so the power input to increase RPM is more than the power input required to increase pitch. I believe increasing pitch has less of an impact to power requirement. 2. I believe a major efficiency loss in relation to propellers is due to tip speed. Tip speed also drastically effects noise. As the propeller tip speed increases, the interaction of high/low pressures on each side of the prop blade clash and cause significant resistance and drag. So it would seem that running a slower, more aggressive prop would provide equivalent thrust with more efficient power consumption. Realizing my above two points are supported by only a partial understanding of the aerodynamics and may not be 100% accurate, I would think the 2 above points could be combined together to develop a CR prop system that provides notable gains. Maximizing the diameter of the prop (within allowable tolerance) as well as utilizing aggressive pitch would allow for slower turning props. With the counter-rotating action of the props, the relative airflow over each prop is increased, again allowing for reduction of prop speed. With the reductions of prop speed provided by these alterations, I would think that would reduce the impact to lags in changes to throttle input. If anyone is able to provide a technically supported response to my above assumptions, I would appreciate the conversation. My apologies for the rambling.
great video you really explained it well. when I made mention of counter-rotating props I did not take into consideration all the other Dynamics that are involved in that... in my mind I'm thinking in the terms of private aircraft not personal aircraft you wear on your back. I have to get my mind wrapped around the paramotor and how they fly and handle.
I know I'm probably not gonna be in the air for months to maybe even over a year; But every time I watch one of these i'm filled with waaay too much excitement. As if I'm gonna be flying tomorrow; Like seriously, I feel like I have to pee! xD
Lots of very positive information ... a comment - on the slow response, on a practical point I recently switched from a single prop boat to contra-rotating prop, the real world acceleration was vastly improved, maybe time to max rpm takes longer (not noticed that) but the twin props were more efficient, less slip, and got me to the speed I wanted much faster. Its acceleration very significantly better than a single prop. As you point out no torque steer, but weight & size is significant , as is cost (Though, I would never go back to single prop on my boat)
Ive flown that 4 prop type of paramotor. It went surprisingly well considering my lack of experience, however the landing was not so hot and I damaged the frame. The design was intended to be very light, but it sacrifices strength. Openppg quit making them and has gone to single prop design as well.
These vids are fantastic. I do think you could easily combine two consecutive videos into one longer vid. This one and the next one, for instance, would still cover just one topic and not be too long. Just my thoughts. They're great either way!
if counter rotating propellers has a disadvantage, why do Russian huge planes have counter rotating propellers and it seems strong and working like the AN-22 huge plane.
Exactly, we need to keep our paramotors light to be able to run for take off. You would not want to carry a huge counter rotating coaxial shaft work lots of gears and bearings on your back.
i go out on a limb and say that the contra rotating prop actually increases a torque reaction. there are two. one is the fact that the prop tends to spin the air. this leads to adverse aerodynamic effects, a helical vortex of air on control surfaces. so a contra-rotating prop eliminates that by combining two opposing helices. a much straighter flow, more predictable. it doesnt eliminate the torque required by the engine to simply spin something. the engine case, the gearbox, mounts, and airframe, all experience a reaction to simply rotating a mass. doesnt matter if its a wheel, a prop, or whatever. a rotating mass requires a torque. consider what happens if you mount the engine at right angles via a bevel drive... you still have this rotating prop mass, and its helical vortex. so a contra rotating prop will eliminate... the torque reaction on the airframe as the mass of the prop rotates one way, the plane the other. we spin two equal masses in opposite directions. check. the torque reaction of rotating air in a helix. check. the gyroscopic forces. check. so thats that. all forces eliminated? class over? lets go home? you sure? think about it. how does the engine work? its cylinder and head exerts a force on a piston and a crank rotates within the case... either the crank and piston move, or the engine does. if you mount the engine at right angles, there is still the torque required to rotate that mass... double the mass, plus gearbox weights and friction... you just increased the moment of inertia of the rotating assembly in the power source. and THAT is bolted to your airframe. you would find that there would be no torque ROLL, but there would now be a torque PITCH. (or we mount the shaft vertical, and produce a yaw?) think about what happens if you hold one of the props stationary. what rotates? in one case, the engine rotates at half the speed of the other prop. in the other case, the prop rotates at twice the speed of the engine. that is, the engine case, the gearbox, and the airframe... all strapped together. one big mass floating in the sky... attempting to spin something... do work against something. a contra rotating prop will always increase that torque reaction. (not so with COUNTER rotating as long as its also the engines running in reverse!) consider a dragster... theres a torque in performing work at the wheels... it tries to do wheelies... but what else happens? the chassis twists up like a corkscrew as the engine torque reacts against the pistons, the crank, the tailshaft, diff, bevel gears... it is doing work in the engine.... its not isolated... you also dont see this when the engine is transverse... most motorbikes.... but you do on BMWs with opposed pistons and longituditional cranks... a plane has a large moment of inertia... a paramotor has a small moment of inertia, but it also has a tiny little motor... keep the rotating mass to a minimum. you eliminate aerodynamic twisting forces, but you do not eliminate the reaction forces that create the thrust in the first place. that engine has to push its piston against something to spin the crank, and that produces a torque in the opposite direction to the crank, proportional to the work done. yes, a helicopter uses twin rotors and eliminates the tail rotor. wtf am i talking about? get off the drugs man... consider... how much mass is in the rotating assembly of the motor, the gearboxes, the blades, versus the overall mass of the vehicle? and its distribution? is it out on the tips? or in on the hubs? the moments of inertia? you counteract certain issues... but you will ALWAYS increase one... an opposite and equal reaction... no matter what.
I'm glad you touched on the quad prop electric powered paragliders. It would be interesting to know if ducting would help or if the weight increase isn't worth the gain of efficiency.
I studied the duct. It would have to be massive to achieve relevant results and the gap between the prop and duct must be 2-5 milimeters. Impossible with our vibrating 2T motors.
I think the biggest problem would be the weight, obviously an idea to check out when we have lighter engines, better materials, it could be good but with the disadvantages it’s not feasible as of now.
Hi great vídeo! Very instructive and pedagogical ! You ve clearly thought a lot about this ! You would be able to use smaller diameter props as I believe that counter rotating props produce more thrust than a single prop of equivalent diameter, therefore the advantage for planes is that you get the performance that would get from a much bigger prop. That you might not be able to use because of ground clearance
Great videos, thanks for posting them. You mentioned in this video about the paramotor with 4 electric motors. I like that concept but I would like to point out that in my opinion there is significant safety concerns with running electric motors with propellers fixed directly to the motors shafts. I believe any paramotor built with brushless dc motors should have propellers mounted onto a primary drive shaft engineered to proper aviation standards not hobby enthusiasts standards. What could be the outcome if one of the propellers came off and went through your canopy??? Also if anyone reading this is contemplating building a dc electric paramotor, please consider some motors are designed as pusher props and some as pullers. If you are considering directly mounting the prop to the motor then be sure to mount the motor in the correct orientation, otherwise catastrophic failure is likely to occur. With respect, :-)
While I somewhat agree with the conclusion of your video, I guess you mention all the facts where this solution won't apply to the ICE engine paramotor. The only reason you may want a CEP Paramotor is for the tremendous acceleration that it may have. Having two smaller power engines, smaller diameter props and a better design caging will make this a super fast toy to play with and only because from CEP you will not be limited on how instant your acceleration may be, your wing may think otherwise :)))) Electric counter props solutions have all the benefits without the additional weight, gearing and complication on ICE power. Plus you get electric engine efficiency, reverse brake option on landing, smaller props diameter, smaller rotation speed, less noise, instant electric torque, and as a bonus, because you pack less ''engine'' and more battery, a better design of a paramotor pod with extended battery may be an option. CEP is known to have way better efficiency because the first prop accelerates the air and the second one takes that accelerated air giving better efficiency for the same hp on a single prop. Overall, I think electric double prop will be the choice for most of new smaller lighter aircraft in the future.
wouldn't it help to make the diameter of the two props about a third smaller to counter the double mass and the double need of motor power and the resistance to react to throttle?
If you're using two propellers, yes it will take more power from the engine to run the same rpm, BUT that's if you use propellers with a typical pitch angle, if you have two of them, why not use propellers that half about HALF the pitch angle so that the two propellers create the WHOLE amount of thrust with 2, and also, you can decrease the mass of the propeller by making each blade width a little less. This would make it more compact, more efficient, and less resistance to turning in the air.
solution... Use a propeller with half the blade angle. Using two normal style propellers on ONE engine is like flying a two engine prop airplane with only one engine powering everything. In other words, if the propeller blade angle is like 15 degrees, then 7-8 degrees would work better for contra-rotation. Two 7 degree rotors can probably do the work of one 15.
At the end of the second world war piston engine powered aircraft had more power than single propellers could handle. To overcome the problems they moved to contra-rotating propellers, this was not just to overcome the problem of torque but also that they just couldn't fit long enough propellers to make the most of the power. A pair of shorter contra-rotating propellers was found to be a better solution than one big single prop. This seems to contradict two of the main objections that using contra-rotating props would be both too heavy and as a result have too much inertia to spin up quickly. Admittedly there is the additional complexity and weight of the gearbox but a pair of contra-rotating props would not be twice the weight of a single prop.
Unfortunately we do not face the same problem with paramotors. We cannot carry stronger engines. This we need to squeeze the most juice of the engine we have.
If we compare the thrust of a coaxial propulsion propeller with a single propeller, then the single propeller should have a diameter of 1.26 times. more. In this regard, the argument about the delay of the throttle valve action is not clear. A larger diameter propeller will simply have more torque and less rpm. The distance between coaxial screws should be at least 10% of their diameter, I don’t see any problems with the layout either.
@3:54-4:15 This prototype is now a reality. OpenPPG X4. I'm flying one. Yes the four small props are not as efficient as one large one. All the other disadvantages of multi prop/motor are not present with electric. It's a wonderful machine to fly but the run time is very short - 20mins - which is a deal breaker for most. It is still quieter, simpler, and more reliable than a 2 stroke. Plus no torque!
A Flywheel would add weight, require a larger engine, and the paramotor would resist turning left or right because of the gyroscopic effect. Note: Airplane engines don't have flywheels, they use aileron and rudder trims for stability.
+Joash Parker yes. Exactly. But it would also slow down the throttle response. And the flywheel would have to be very heavy. Times heavier than prop itself because the prop has large diameter.
🔶Our infinitely variable FrictionLess gear tech enables >10X gear box reduction‼ Non-coaxial contra architecture is possible. How? I'm a triple engineer. We will also bring out an efficient, clean, noise-less, ultra power dense rotary engine what will use any fuel or mixture thereof 😉🧐 🔶
Found this looking for coaxial cable. Seems you need a modified Lynch type (Etek, Agni) motor with central stator, reversed magnets on one side, magnets embedded in prop ring. The motor halves are principally held together with magnetic flux. ruclips.net/video/zzDcjMdiHms/видео.html You save weight by driving the "meat" of each prop with magnetic coupling instead of structure transferring force inward to a shaft, then back out through the prop. Allows centerless props and minimal static structure because it no longer needs to resist the full torque of the motor. Cedric Lynch himself might even design it for you if you ask nicely. en.wikipedia.org/wiki/Solution_F/Chretien_Helicopter
Use more props that are smaller, like in a spider web, use a light material and install 4, 6, 8, or even 10 rotor conected by drive belts, seems doable but i´d need 30000 to build a prototype
Exactly my thoughts. Twice as many props with a smaller diameter. Roughly equal weight, roughly equal thrust. Counter rotation increases efficiency, which offsets the smaller size. It's NOT for twice the thrust, it's for a more compact design.
FYI: That's "4 electric motors", not "4 electric engines". I will quote in part, "The real difference, is the fact that "motors" run on electricity, while "engines" run on combustion. However, many people interchange the usage of these words: On the rare occasions we encounter one, we refer to a steam locomotive as an engine, the same word that we give to the motive power of an aircraft." From english.stackexchange.com/questions/42027/semantic-difference-between-engine-and-motor
perhaps good for direct downwind faster that the wind vehicle: turbines? hmmmmmmmmmm....... all the cautions of air powered is negated. perhaps only up sides
I have been considering designing a twin prop system based on this ruclips.net/video/iEx3dJTIjww/видео.html No torque. Less complex than the system you present. Weight could still be an issue. Waddya think?
I give you your solution: ruclips.net/video/C4kp6PhSz8c/видео.html This requires a slightly oval cage and some additional setback. Slightly smaller props would be used. leave it to the russian
Consider 2 motors back to back, one pushing the other pulling. Simple, redundant. ruclips.net/video/p4Od7c_Jk-o/видео.html for the concept. However, I would use 2 large props behind the pilot.
This is probably the only informative scout video that is very flawed,most of the drawbacks are exaggerated or wrong. The reason being is most likely it would not suit scout economically as it would directly compete with their no torgue design and could not be used with their frame. Not to bash scouts design as it works okay and currently is the best on the market . Counter rotating props would be heavier,aproximately by 1,5-2kg, could be less with good design.Easiest way to do it would be through a gear driven reduction drive and use a chain next to the gears for the second shaft. Propeller diameter would be smaller,since inertia is effected by the radius of the mass compared to center of the shaft,the inertia would be less than compared to a 4 blade propeller.There would be no gyroscopic effect as that would cancel itself out.Since the propeller diameter would be smaller and the blade flex would be less the first propeller could be moved forwards.The second propeller can be placed close to the first propeller making the stick out less of a issue,only reason to place the second propeller alot more aft is to further gain efficiency. It really does not require a complex expensive solution as stated in the video.One drawback would be the thinner shafts necessary with counter rotating propellers would be more prone to damage by prop strike. Cost would increase around 400-500e compared to a standard 2 blade setup with the props being the largest cause to increase of cost. Only reason we are not seing this on the market is it would need to be designed by the engine manufacturers together with propeller manufacturers and innovation is not really something these companies are known for, still sporting the wg8 carb from 80´ husky chain saw.
In my opinion contrarotator is not good couse these sistem using like that disturbing the efficience plus will destroy engine couse what it couse is just compressing air flow to have less noise u hace to separete a bit anyway sound is a mass too wich influence on it too.realy in any flying things i dont like it . maybe in others application can be very efficient.own opinion ...no need to be that way.up to every one likes or so
I don't think it is possible to use the counter rotating propellers in a paramotor due to reasons explained in the video. I know some have tried and it was not feasible. I have seen one prototype myself. I cannot discuss on efficiency and thrust as I don't feel qualified to do so.
It is not possible just simply add another counter rotating prop to the same engine. If twice as many blades used, these need to be either lower angle, or shorter chord of the profile (blades less wide) or both. The horsepower of the engine is given and the goal is to convert it into trust the most efficient way. Now the question is will the counter rotating props be more efficient than one? I am not qualified to answer that as I did not do this research. Could easily be the the second prop would actually reduce overall efficiency as it will work in a very turbulent prop wash from the first. But I don't know.
what is torque? u cant just throw in words and concepts, hoping the listener understand them. if they did, then they would also understand the rest, and you won't need to make this video
@@SCOUTaviation Uh, I see. I need to spend a few hours watching all there is by the make of these in order to understand a single word that can be easily explained from one episode to the other. Not a good teacher
One of the two are going to spin in the same direction as the motor’s armature or rotor, adding to the torque of that prop. How is that compensated for?
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Don't know if it's just me but waiting for the next video to be released is like waiting for the next episode of your favourite Tv show. I don't know why people haven't done this on RUclips before. Keep it up.
I really appreciate your intellectual reviews of all this. I do have some "conceptual" questions regarding the cost/benefits of CR prop systems.
1. The relative air velocity over the airfoil of the prop is what develops thrust. Thrust can be increased by either increasing relative air velocity (increase RPM) or increasing pitch of the prop. Both of these require additional power input, however increasing RPM has a squared component so the power input to increase RPM is more than the power input required to increase pitch. I believe increasing pitch has less of an impact to power requirement.
2. I believe a major efficiency loss in relation to propellers is due to tip speed. Tip speed also drastically effects noise. As the propeller tip speed increases, the interaction of high/low pressures on each side of the prop blade clash and cause significant resistance and drag. So it would seem that running a slower, more aggressive prop would provide equivalent thrust with more efficient power consumption.
Realizing my above two points are supported by only a partial understanding of the aerodynamics and may not be 100% accurate, I would think the 2 above points could be combined together to develop a CR prop system that provides notable gains. Maximizing the diameter of the prop (within allowable tolerance) as well as utilizing aggressive pitch would allow for slower turning props. With the counter-rotating action of the props, the relative airflow over each prop is increased, again allowing for reduction of prop speed. With the reductions of prop speed provided by these alterations, I would think that would reduce the impact to lags in changes to throttle input.
If anyone is able to provide a technically supported response to my above assumptions, I would appreciate the conversation. My apologies for the rambling.
great video you really explained it well. when I made mention of counter-rotating props I did not take into consideration all the other Dynamics that are involved in that... in my mind I'm thinking in the terms of private aircraft not personal aircraft you wear on your back. I have to get my mind wrapped around the paramotor and how they fly and handle.
Super video lepo je slediti vašim posnetkom
I know I'm probably not gonna be in the air for months to maybe even over a year; But every time I watch one of these i'm filled with waaay too much excitement. As if I'm gonna be flying tomorrow; Like seriously, I feel like I have to pee! xD
Lots of very positive information ... a comment - on the slow response, on a practical point I recently switched from a single prop boat to contra-rotating prop, the real world acceleration was vastly improved, maybe time to max rpm takes longer (not noticed that) but the twin props were more efficient, less slip, and got me to the speed I wanted much faster. Its acceleration very significantly better than a single prop. As you point out no torque steer, but weight & size is significant , as is cost (Though, I would never go back to single prop on my boat)
Ive flown that 4 prop type of paramotor. It went surprisingly well considering my lack of experience, however the landing was not so hot and I damaged the frame. The design was intended to be very light, but it sacrifices strength.
Openppg quit making them and has gone to single prop design as well.
These vids are fantastic. I do think you could easily combine two consecutive videos into one longer vid. This one and the next one, for instance, would still cover just one topic and not be too long. Just my thoughts. They're great either way!
Milo: Have you thought of marketing a T-Shirt with the Scout Paramotor Geometry drawing? Fashionably COOL!
good hint. I already know which drawing I would use...
Awesome idea!
if counter rotating propellers has a disadvantage, why do Russian huge planes have counter rotating propellers and it seems strong and working like the AN-22 huge plane.
Exactly, we need to keep our paramotors light to be able to run for take off.
You would not want to carry a huge counter rotating coaxial shaft work lots of gears and bearings on your back.
i go out on a limb and say that the contra rotating prop actually increases a torque reaction.
there are two. one is the fact that the prop tends to spin the air. this leads to adverse aerodynamic effects, a helical vortex of air on control surfaces.
so a contra-rotating prop eliminates that by combining two opposing helices. a much straighter flow, more predictable.
it doesnt eliminate the torque required by the engine to simply spin something. the engine case, the gearbox, mounts, and airframe, all experience a reaction to simply rotating a mass. doesnt matter if its a wheel, a prop, or whatever. a rotating mass requires a torque.
consider what happens if you mount the engine at right angles via a bevel drive... you still have this rotating prop mass, and its helical vortex. so a contra rotating prop will eliminate... the torque reaction on the airframe as the mass of the prop rotates one way, the plane the other. we spin two equal masses in opposite directions. check.
the torque reaction of rotating air in a helix. check.
the gyroscopic forces. check. so thats that.
all forces eliminated? class over? lets go home?
you sure?
think about it.
how does the engine work? its cylinder and head exerts a force on a piston and a crank rotates within the case... either the crank and piston move, or the engine does.
if you mount the engine at right angles, there is still the torque required to rotate that mass... double the mass, plus gearbox weights and friction... you just increased the moment of inertia of the rotating assembly in the power source. and THAT is bolted to your airframe. you would find that there would be no torque ROLL, but there would now be a torque PITCH. (or we mount the shaft vertical, and produce a yaw?)
think about what happens if you hold one of the props stationary. what rotates?
in one case, the engine rotates at half the speed of the other prop.
in the other case, the prop rotates at twice the speed of the engine.
that is, the engine case, the gearbox, and the airframe... all strapped together. one big mass floating in the sky... attempting to spin something... do work against something. a contra rotating prop will always increase that torque reaction. (not so with COUNTER rotating as long as its also the engines running in reverse!)
consider a dragster... theres a torque in performing work at the wheels... it tries to do wheelies...
but what else happens?
the chassis twists up like a corkscrew as the engine torque reacts against the pistons, the crank, the tailshaft, diff, bevel gears... it is doing work in the engine.... its not isolated... you also dont see this when the engine is transverse... most motorbikes.... but you do on BMWs with opposed pistons and longituditional cranks...
a plane has a large moment of inertia...
a paramotor has a small moment of inertia, but it also has a tiny little motor... keep the rotating mass to a minimum.
you eliminate aerodynamic twisting forces, but you do not eliminate the reaction forces that create the thrust in the first place. that engine has to push its piston against something to spin the crank, and that produces a torque in the opposite direction to the crank, proportional to the work done.
yes, a helicopter uses twin rotors and eliminates the tail rotor. wtf am i talking about? get off the drugs man...
consider...
how much mass is in the rotating assembly of the motor, the gearboxes, the blades, versus the overall mass of the vehicle? and its distribution? is it out on the tips? or in on the hubs? the moments of inertia?
you counteract certain issues... but you will ALWAYS increase one... an opposite and equal reaction... no matter what.
i like that 4-prop design
Dream of a Contra-Rotating Toroidal Prop.
I'm glad you touched on the quad prop electric powered paragliders. It would be interesting to know if ducting would help or if the weight increase isn't worth the gain of efficiency.
I studied the duct. It would have to be massive to achieve relevant results and the gap between the prop and duct must be 2-5 milimeters. Impossible with our vibrating 2T motors.
These are very informative. I am very impressed with the effort you have put into these!
interesting and i learn a lot. thx
Thanks for the content!
Do u know about the multi engine aircrafts?
Why the companies doesn't use counter rotating props like Senecas?
I think the biggest problem would be the weight, obviously an idea to check out when we have lighter engines, better materials, it could be good but with the disadvantages it’s not feasible as of now.
Thankyou so much for sharing. This helped me a lot. Thankyou ☺
Interesting discussion. That looks like Mojave???
Hi great vídeo! Very instructive and pedagogical ! You ve clearly thought a lot about this ! You would be able to use smaller diameter props as I believe that counter rotating props produce more thrust than a single prop of equivalent diameter, therefore the advantage for planes is that you get the performance that would get from a much bigger prop. That you might not be able to use because of ground clearance
Just mount a big blower on your back :). This arrangement could torque like the car wheel.
Great videos, thanks for posting them.
You mentioned in this video about the paramotor with 4 electric motors.
I like that concept but I would like to point out that in my opinion there is significant safety concerns with running electric motors with propellers fixed directly to the motors shafts.
I believe any paramotor built with brushless dc motors should have propellers mounted onto a primary drive shaft engineered to proper aviation standards not hobby enthusiasts standards.
What could be the outcome if one of the propellers came off and went through your canopy???
Also if anyone reading this is contemplating building a dc electric paramotor, please consider some motors are designed as pusher props and some as pullers.
If you are considering directly mounting the prop to the motor then be sure to mount the motor in the correct orientation, otherwise catastrophic failure is likely to occur.
With respect, :-)
While I somewhat agree with the conclusion of your video, I guess you mention all the facts where this solution won't apply to the ICE engine paramotor. The only reason you may want a CEP Paramotor is for the tremendous acceleration that it may have. Having two smaller power engines, smaller diameter props and a better design caging will make this a super fast toy to play with and only because from CEP you will not be limited on how instant your acceleration may be, your wing may think otherwise :)))) Electric counter props solutions have all the benefits without the additional weight, gearing and complication on ICE power. Plus you get electric engine efficiency, reverse brake option on landing, smaller props diameter, smaller rotation speed, less noise, instant electric torque, and as a bonus, because you pack less ''engine'' and more battery, a better design of a paramotor pod with extended battery may be an option. CEP is known to have way better efficiency because the first prop accelerates the air and the second one takes that accelerated air giving better efficiency for the same hp on a single prop. Overall, I think electric double prop will be the choice for most of new smaller lighter aircraft in the future.
wouldn't it help to make the diameter of the two props about a third smaller to counter the double mass and the double need of motor power and the resistance to react to throttle?
If you're using two propellers, yes it will take more power from the engine to run the same rpm, BUT that's if you use propellers with a typical pitch angle, if you have two of them, why not use propellers that half about HALF the pitch angle so that the two propellers create the WHOLE amount of thrust with 2, and also, you can decrease the mass of the propeller by making each blade width a little less. This would make it more compact, more efficient, and less resistance to turning in the air.
Two lighter props will airways be heavier than one.
The counter rotating shaft is the very heavy component
solution... Use a propeller with half the blade angle. Using two normal style propellers on ONE engine is like flying a two engine prop airplane with only one engine powering everything.
In other words, if the propeller blade angle is like 15 degrees, then 7-8 degrees would work better for contra-rotation. Two 7 degree rotors can probably do the work of one 15.
what about friction? does it burn more oil?
At the end of the second world war piston engine powered aircraft had more power than single propellers could handle. To overcome the problems they moved to contra-rotating propellers, this was not just to overcome the problem of torque but also that they just couldn't fit long enough propellers to make the most of the power. A pair of shorter contra-rotating propellers was found to be a better solution than one big single prop. This seems to contradict two of the main objections that using contra-rotating props would be both too heavy and as a result have too much inertia to spin up quickly. Admittedly there is the additional complexity and weight of the gearbox but a pair of contra-rotating props would not be twice the weight of a single prop.
Unfortunately we do not face the same problem with paramotors. We cannot carry stronger engines. This we need to squeeze the most juice of the engine we have.
If we compare the thrust of a coaxial propulsion propeller with a single propeller, then the single propeller should have a diameter of 1.26 times. more. In this regard, the argument about the delay of the throttle valve action is not clear. A larger diameter propeller will simply have more torque and less rpm. The distance between coaxial screws should be at least 10% of their diameter, I don’t see any problems with the layout either.
@3:54-4:15 This prototype is now a reality. OpenPPG X4. I'm flying one. Yes the four small props are not as efficient as one large one. All the other disadvantages of multi prop/motor are not present with electric. It's a wonderful machine to fly but the run time is very short - 20mins - which is a deal breaker for most. It is still quieter, simpler, and more reliable than a 2 stroke. Plus no torque!
Would some kind of gyro/flywheel work?
would still add alot of weight
A Flywheel would add weight, require a larger engine, and the paramotor would resist turning left or right because of the gyroscopic effect. Note: Airplane engines don't have flywheels, they use aileron and rudder trims for stability.
a fly wheel would only solve the acelleration torque not the constant speed torque
+Joash Parker yes. Exactly.
But it would also slow down the throttle response.
And the flywheel would have to be very heavy. Times heavier than prop itself because the prop has large diameter.
Ah yes of course, once the acceleration has stopped it would only provide resistance to further changes, making it very sluggish indeed.
Counter rotating propellers are used on some planes
You should invent a "tail rotor" that protrudes from the top and faces perpendicular to the main prop axis (like a helicopter) ;)
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2:00 and twice as much air resistance.
Found this looking for coaxial cable. Seems you need a modified Lynch type (Etek, Agni) motor with central stator, reversed magnets on one side, magnets embedded in prop ring. The motor halves are principally held together with magnetic flux. ruclips.net/video/zzDcjMdiHms/видео.html You save weight by driving the "meat" of each prop with magnetic coupling instead of structure transferring force inward to a shaft, then back out through the prop. Allows centerless props and minimal static structure because it no longer needs to resist the full torque of the motor. Cedric Lynch himself might even design it for you if you ask nicely. en.wikipedia.org/wiki/Solution_F/Chretien_Helicopter
Use more props that are smaller, like in a spider web, use a light material and install 4, 6, 8, or even 10 rotor conected by drive belts, seems doable but i´d need 30000 to build a prototype
Check our video on large vs small props
Exactly my thoughts. Twice as many props with a smaller diameter. Roughly equal weight, roughly equal thrust. Counter rotation increases efficiency, which offsets the smaller size. It's NOT for twice the thrust, it's for a more compact design.
FYI: That's "4 electric motors", not "4 electric engines". I will quote in part, "The real difference, is the fact that "motors" run on electricity, while "engines" run on combustion. However, many people interchange the usage of these words: On the rare occasions we encounter one, we refer to a steam locomotive as an engine, the same word that we give to the motive power of an aircraft." From english.stackexchange.com/questions/42027/semantic-difference-between-engine-and-motor
Seafire Fr.42 its contra prop
perhaps good for direct downwind faster that the wind vehicle: turbines? hmmmmmmmmmm....... all the cautions of air powered is negated. perhaps only up sides
DDWFTTW vechicles:
I have a few ideas
Counter rotating propeller only will work on electric motors.
4 props? Lol I had it in mind when I thought "Wait how do drones compensate torque... 4 props... What if we do the same with paramotors?"
Small props are less efficient than large ones. Aircraft manufacturers try to use a large one whenever possible
wath about 3 4 5 6 blade propeller
Twin electric
I can solve 4 problems out of 5. It can be light, cheap, simple and effective.
I have been considering designing a twin prop system based on this
ruclips.net/video/iEx3dJTIjww/видео.html
No torque. Less complex than the system you present.
Weight could still be an issue.
Waddya think?
I am curious! Go for it!
I give you your solution:
ruclips.net/video/C4kp6PhSz8c/видео.html
This requires a slightly oval cage and some additional setback. Slightly smaller props would be used.
leave it to the russian
Opposed piston engine anyone?
Consider 2 motors back to back, one pushing the other pulling. Simple, redundant. ruclips.net/video/p4Od7c_Jk-o/видео.html for the concept. However, I would use 2 large props behind the pilot.
Works on planes, too heavy on everything else
This is probably the only informative scout video that is very flawed,most of the drawbacks are exaggerated or wrong. The reason being is most likely it would not suit scout economically as it would directly compete with their no torgue design and could not be used with their frame. Not to bash scouts design as it works okay and currently is the best on the market . Counter rotating props would be heavier,aproximately by 1,5-2kg, could be less with good design.Easiest way to do it would be through a gear driven reduction drive and use a chain next to the gears for the second shaft.
Propeller diameter would be smaller,since inertia is effected by the radius of the mass compared to center of the shaft,the inertia would be less than compared to a 4 blade propeller.There would be no gyroscopic effect as that would cancel itself out.Since the propeller diameter would be smaller and the blade flex would be less the first propeller could be moved forwards.The second propeller can be placed close to the first propeller making the stick out less of a issue,only reason to place the second propeller alot more aft is to further gain efficiency. It really does not require a complex expensive solution as stated in the video.One drawback would be the thinner shafts necessary with counter rotating propellers would be more prone to damage by prop strike. Cost would increase around 400-500e compared to a standard 2 blade setup with the props being the largest cause to increase of cost. Only reason we are not seing this on the market is it would need to be designed by the engine manufacturers together with propeller manufacturers and innovation is not really something these companies are known for, still sporting the wg8 carb from 80´ husky chain saw.
In my opinion contrarotator is not good couse these sistem using like that disturbing the efficience plus will destroy engine couse what it couse is just compressing air flow to have less noise u hace to separete a bit anyway sound is a mass too wich influence on it too.realy in any flying things i dont like it . maybe in others application can be very efficient.own opinion ...no need to be that way.up to every one likes or so
This video is flawed and incomplete, no mention of thrust, how much is the difference between single and double as well as efficiency
I don't think it is possible to use the counter rotating propellers in a paramotor due to reasons explained in the video.
I know some have tried and it was not feasible. I have seen one prototype myself.
I cannot discuss on efficiency and thrust as I don't feel qualified to do so.
@@SCOUTaviation then, what's the point?? Does the power thrust increases by 100%? 50%?? 20%?? Compared to single propeller....
It is not possible just simply add another counter rotating prop to the same engine. If twice as many blades used, these need to be either lower angle, or shorter chord of the profile (blades less wide) or both.
The horsepower of the engine is given and the goal is to convert it into trust the most efficient way. Now the question is will the counter rotating props be more efficient than one?
I am not qualified to answer that as I did not do this research. Could easily be the the second prop would actually reduce overall efficiency as it will work in a very turbulent prop wash from the first. But I don't know.
@@SCOUTaviation fine.... I'll watch other videos and keep looking
what is torque? u cant just throw in words and concepts, hoping the listener understand them. if they did, then they would also understand the rest, and you won't need to make this video
This is one video of a series and torque was explained earlier. Go and check out the whole series, your will learn a lot for sure
@@SCOUTaviation Uh, I see. I need to spend a few hours watching all there is by the make of these in order to understand a single word that can be easily explained from one episode to the other. Not a good teacher
One of the two are going to spin in the same direction as the motor’s armature or rotor, adding to the torque of that prop. How is that compensated for?
Just add more weight to the one rotation opposite.