Electric tail rotor; an alternative?
I can see only one thing that speaks for an electric TR and that is that you wouldn't need pitch controlled blades. I'll mention a few things that come to mind that speaks against it, although I'm sure there are many more:
- I'm sure there's a lot of computer control in most modern helicopters already, but this would have to be entirely computer controlled to be at all flyable. That would open up a new can of worms when it comes to safety. I know that "fly-by-wire" is popular these days, but personally I only consider it "safe" as long as everybody is equipped with ejection seats.
- The reason they use electric motors on ships is first and foremost because it's difficult to get the mechanical energy to where you want it. Imagine the arrangement of driveshafts and gears that would be needed to transfer the power from the engine(s) to multiple azimuth thrusters placed on different locations, some probably near the bow. On trains they often do the same, but from what I understand that's for similar reasons (you want drive on as many wheels as possible because trains generally have bad traction) and because making gearboxes that can take the punishment over time is difficult. However you twist it, converting mechanical energy into electrical energy and then back again means that you'll both have a lot of extra potential points of failure and waste a significant part of the energy. Driveshafts and gearboxes waste energy too (through friction in bearings etc.), but considering how simple (geometrically) this is on a helicopter I'm convinced that using driveshafts and gearboxes is much more efficient.
- There's nothing inherently "environmental friendly" about electrical motors. It all depends on what form the energy is available in to start with. If you use a combustion engine to turn fuel into energy, you have mechanical energy as the source. What is considered "environmental unfriendly" is the combustion engine itself, converting the energy to electricity after the engine makes no sense (although some cars do this to ride the hype). If you have electricity as the power source using for example a battery or fuel cells, things are very different.
- As mentioned above, the only "gain" by using an electrical TR that I can see it that you wouldn't need pitch controlled blades. That said, changing the pitch is very quick and doesn't take a lot of power. The RPM is already there, ready to be used. A fixed pitch blade rotor would have to vary the RPM instead, and I believe this would be much too slow to be practical due to the inertia in the rotor. I guess that if you could make it by some revolutionary new hyped nano-materials that's stronger than steel but weighs nothing, the inertia problem could be overcome. I don't know of any such materials outside the world of hype though.
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Sorry as this seems to have drifted from the main thread.
The advantages of an electric tail rotor is that it can run at speeds independent of the main rotor. This allows the design to not be limited to one compromise. It, importantly, gives greater control over noise.
The assumption that a motor would be as heavy as a TGB, IGB, MGB tail pickoff and driveshaft is not one that I would make.
The advantages of an electric tail rotor is that it can run at speeds independent of the main rotor. This allows the design to not be limited to one compromise. It, importantly, gives greater control over noise.
The assumption that a motor would be as heavy as a TGB, IGB, MGB tail pickoff and driveshaft is not one that I would make.
Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
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YouTube linky: electric tail rotor
Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
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YouTube linky: electric tail rotor
Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
Great discussion chaps, but don't put your patent applications in just yet, think you've been beaten to it... If I'm not mistaken the team at Leonardo won an award for their work from the RAeS the other evening as well!
Most things have already been tried as already mentioned in this thread. What would surprise me is if an electric tail rotor would be competitive when it comes to reliability and efficiency as long as the power plant is a combustion engine.
Here is a paper on the model shown in the youtube clip, although I didn't see much of interest in there: http://www.cleansky.eu/sites/default...3_-_eletad.pdf
It's obvious that an electrical TR could be made, it would probably be much cheaper to produce than the current mechanical solutions as well. What I seriously question is whether it would be "competitive" with regards to the criteria that matter, especially when it comes to safety. How would you do a autorotation with an electrical tail rotor?
Here is a paper on the model shown in the youtube clip, although I didn't see much of interest in there: http://www.cleansky.eu/sites/default...3_-_eletad.pdf
It's obvious that an electrical TR could be made, it would probably be much cheaper to produce than the current mechanical solutions as well. What I seriously question is whether it would be "competitive" with regards to the criteria that matter, especially when it comes to safety. How would you do a autorotation with an electrical tail rotor?
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Nadar, there are efficiencies to be gained by the ability to vary tail rotor speed. It allows a designer to move the compromise points. Plus as I stated before the ability to tailor the noise footprint.
As to autorotation, how much torque is the tail rotor dealing?
As to autorotation, how much torque is the tail rotor dealing?
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As to autorotation, how much torque is the tail rotor dealing?
Irrespective of how the turning rotor is actually powered, it still needs a blade pitch control system. Varying the speed of rotation isn't the full answer.
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b) Did anyone assume it wouldn't work in autorotation? I certainly didn't. However, the tail rotor would still absorb a lot of energy even in autorotation so presumably its electrical power generator would need to be driven by the main rotor transmission, or a very large capacity battery would be required if engine driven generators no longer provided electrical power.
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a) I'm not familiar with the term ROM%
b) Did anyone assume it wouldn't work in autorotation? I certainly didn't. However, the tail rotor would still absorb a lot of energy even in autorotation so presumably its electrical power generator would need to be driven by the main rotor transmission, or a very large capacity battery would be required if engine driven generators no longer provided electrical power.
b) Did anyone assume it wouldn't work in autorotation? I certainly didn't. However, the tail rotor would still absorb a lot of energy even in autorotation so presumably its electrical power generator would need to be driven by the main rotor transmission, or a very large capacity battery would be required if engine driven generators no longer provided electrical power.
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Surely you cannot be serious?
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ShyTorque, my apologies, ROM is Rough Order of Magnitude. I ask because this determines the power demand at a critical phase.
Nadar seems to have implied that auto with an ETR would be different to "conventional". I'm not sure why this would be the case, in auto I would presume a design where the MGB is still driving the generators. Question for my own interest, how many helicopters out there revert to battery when in autorotation and how many retain electrical generation?
note: during "conventional" autorotation, the tail rotor is powered by the MGB.
Nadar seems to have implied that auto with an ETR would be different to "conventional". I'm not sure why this would be the case, in auto I would presume a design where the MGB is still driving the generators. Question for my own interest, how many helicopters out there revert to battery when in autorotation and how many retain electrical generation?
note: during "conventional" autorotation, the tail rotor is powered by the MGB.
Last edited by dClbydalpha; 1st Dec 2018 at 19:46. Reason: Subsequent posts
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I had a small RC helicopter with an electric tail rotor once. Worked fine until it sparked a few times and stop dead.
I dont think this helps any. Just thought I would share
playing it safe since the mods deleted my last post
I dont think this helps any. Just thought I would share
playing it safe since the mods deleted my last post
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