what is the best helicopter in autorotation
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zeeoo,
Cold jets with a piston engine and added compressor?
How could a piston engine compete with a turbine that has a high power to weight ratio and a built in compressor?
A better plan might be installing turbines at the tip. Hiller was working on that also. R/C model people are building small turbojets, not sure if they have gotten to building turbofans, that could be interesting.
Electric turbofans is another idea, used in the R/C world. A small battery could provide a surge of power for a jump takeoff.
Cold jets with a piston engine and added compressor?
How could a piston engine compete with a turbine that has a high power to weight ratio and a built in compressor?
A better plan might be installing turbines at the tip. Hiller was working on that also. R/C model people are building small turbojets, not sure if they have gotten to building turbofans, that could be interesting.
Electric turbofans is another idea, used in the R/C world. A small battery could provide a surge of power for a jump takeoff.
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Slow rotor,
my numbers for the Djinn are an airflow of 1.1Kgs/sec.
A turbocharger like the garrett GT40 can provide 1kg/sec at 2.5 bars. Another example is the ROTREX superchargers, the bigger can provide 0.8 Kg at 2 bars, i asked their eng team and they estimate the power required to run 2 units at about 75 Kw.
BUT using cold jets for prerotation is different than for main power source. The airmass needed is far less since you don't power the rotor with it. BTW, for a gyro, the rotor doesn't acts at high AoA.
According to rough calculus,i have estimated that i can get 25 lb of thrust on each blade.
You can't compete with a gas turbine but the Artouste and Palouste are old generation turbines.
talking about RC turbines, i believe there's something to do, check this link : http://www.microjeteng.com/prop.html
but the price must be pretty high.
Thanks
Victor
my numbers for the Djinn are an airflow of 1.1Kgs/sec.
A turbocharger like the garrett GT40 can provide 1kg/sec at 2.5 bars. Another example is the ROTREX superchargers, the bigger can provide 0.8 Kg at 2 bars, i asked their eng team and they estimate the power required to run 2 units at about 75 Kw.
BUT using cold jets for prerotation is different than for main power source. The airmass needed is far less since you don't power the rotor with it. BTW, for a gyro, the rotor doesn't acts at high AoA.
According to rough calculus,i have estimated that i can get 25 lb of thrust on each blade.
You can't compete with a gas turbine but the Artouste and Palouste are old generation turbines.
talking about RC turbines, i believe there's something to do, check this link : http://www.microjeteng.com/prop.html
but the price must be pretty high.
Thanks
Victor
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zeeoo,
Try not to lose sight that power is power, so the rotor with tip jets eats power based on the thrust, disk loading and figure of merit. The tip jet nozzles will eat more power because they create high drag in the worst spot. The power losses due to fluid flow issues in the hub manifold and the blades (assuming cold cycle) are very high, perhaps 10 to 20% of the total power (vice 3% for mechanical transmissions). Losses at the tip nozzel for hot cycle are very high as well.
These factors generall cost so much power that the hover envelope of these machines is small compared with the conventonal helos, and the fuel flow in a hover is simply eye-watering.
The way to make some hay on this is like the rotodyne, where the powered tip is used for a few minutes at each end of the journey, of course.
Try not to lose sight that power is power, so the rotor with tip jets eats power based on the thrust, disk loading and figure of merit. The tip jet nozzles will eat more power because they create high drag in the worst spot. The power losses due to fluid flow issues in the hub manifold and the blades (assuming cold cycle) are very high, perhaps 10 to 20% of the total power (vice 3% for mechanical transmissions). Losses at the tip nozzel for hot cycle are very high as well.
These factors generall cost so much power that the hover envelope of these machines is small compared with the conventonal helos, and the fuel flow in a hover is simply eye-watering.
The way to make some hay on this is like the rotodyne, where the powered tip is used for a few minutes at each end of the journey, of course.
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zeeoo,
If your interested in just autogyro prespin for takeoff then you probably should consider very simple methods.
How about water jet at tip? Sounds silly, but I know of several models that used water ejected for takeoff.
Water is about 800 times the mass of air. And once it is ejected in your rotor spinup then the weight is gone but the rotor energy remains.
If your interested in just autogyro prespin for takeoff then you probably should consider very simple methods.
How about water jet at tip? Sounds silly, but I know of several models that used water ejected for takeoff.
Water is about 800 times the mass of air. And once it is ejected in your rotor spinup then the weight is gone but the rotor energy remains.
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Slow rotor :
your system has interest, but the way to produce high pressure water jets may be heavier than high pressure air, the water leaks may quickly degrade the rotor mechanism.. air leaks don't.... BTW this is a one or two-use system and i am not for that.....
Nick,
very interesting.. let me try to defend my idea...
(1) yes, i feel the tip nozzles induce great losses..that's why i think in using wing-nozzles : http://zeeoo.free.fr/gyro/nozzle.jpg
the drag and little pitch up moment may be neglectable, BTW, the air-jet doesnt act where the tip-vortex is, and this vortex decreases the efficiency of the tip jet, right?
The use of a squared nozzle is made to avoid the air spinning at the output, this effet can be improved by the use of a nozzle grid (like quiteners in wind tunnels).
(2) You took the example of the rotodyne : YES if think in using the tip jets only for pre rotation and a residual in-flight power..
Let's say that i would share the power by 35 hp to the comp and 50 to the prop (that is enough for FW flight).
The weight of a supercharger w/oil cooling circuit is about 12 lbs.
it may be a little diffiult to do, but, if it works, that adds a great safety feature and allows a higher fw speed.
Thanks for your kind and interesting contribution.
Victor
your system has interest, but the way to produce high pressure water jets may be heavier than high pressure air, the water leaks may quickly degrade the rotor mechanism.. air leaks don't.... BTW this is a one or two-use system and i am not for that.....
Nick,
very interesting.. let me try to defend my idea...
(1) yes, i feel the tip nozzles induce great losses..that's why i think in using wing-nozzles : http://zeeoo.free.fr/gyro/nozzle.jpg
the drag and little pitch up moment may be neglectable, BTW, the air-jet doesnt act where the tip-vortex is, and this vortex decreases the efficiency of the tip jet, right?
The use of a squared nozzle is made to avoid the air spinning at the output, this effet can be improved by the use of a nozzle grid (like quiteners in wind tunnels).
(2) You took the example of the rotodyne : YES if think in using the tip jets only for pre rotation and a residual in-flight power..
Let's say that i would share the power by 35 hp to the comp and 50 to the prop (that is enough for FW flight).
The weight of a supercharger w/oil cooling circuit is about 12 lbs.
it may be a little diffiult to do, but, if it works, that adds a great safety feature and allows a higher fw speed.
Thanks for your kind and interesting contribution.
Victor
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quadrirotor,
"Synchropter is ideal to autorotate after a power shut down as the nose goes down when there is no torque at the rotors!"
True. This rotation about the craft's lateral axis is due to the angle of the masts off the vertical and the breaststroke (inside forward) rotation of the rotors. Kaman may have found it a little 'too' ideal.
On an early model of the Huskie they directed the exhaust downward in an apparent attempt to reduce this pitching on the loss of power.
This is one of a number of reasons for increasing the rigidity of intermeshing rotors. Rigid rotors will allow for a reduction in the angle between the two masts and this reduces the pitch component of the torque of the main rotors.
_____________________
zeeoo,
The reason for questioning your project is that I believe your 'gyrocopter' will not be marketable in the US Sport plane/pilot category, should you desire to do so. A collective control, for a jump takeoff, or helicopter style cyclic control, which is necessary for a rotor with more than two blades, will not be accepted.
Dave
Editied to remove the idiotic comments on electric rotorcraft.
"Synchropter is ideal to autorotate after a power shut down as the nose goes down when there is no torque at the rotors!"
True. This rotation about the craft's lateral axis is due to the angle of the masts off the vertical and the breaststroke (inside forward) rotation of the rotors. Kaman may have found it a little 'too' ideal.
On an early model of the Huskie they directed the exhaust downward in an apparent attempt to reduce this pitching on the loss of power. This is one of a number of reasons for increasing the rigidity of intermeshing rotors. Rigid rotors will allow for a reduction in the angle between the two masts and this reduces the pitch component of the torque of the main rotors.
_____________________
zeeoo,
The reason for questioning your project is that I believe your 'gyrocopter' will not be marketable in the US Sport plane/pilot category, should you desire to do so. A collective control, for a jump takeoff, or helicopter style cyclic control, which is necessary for a rotor with more than two blades, will not be accepted.
Dave
Editied to remove the idiotic comments on electric rotorcraft.
Last edited by Dave_Jackson; 7th Feb 2005 at 23:52.
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Dave_Jackson,
I'v been told about this limitation. But i don't plan to market something at the moment. XWe have not this limitation in france and europe.
BTW, a rumour says that Ermie Boyette (dominator )and Dick Degraw are preparing a kind of 3 bladed rotor with jump take off capabilities... i bet they will find the right category... i bet the 3 bladed rotors offer is prone to increase.
BTW some 3 bladed gyros (lioré and la cierva) didn't have a helicopter-like cyclic control but a "teetering" 3 bladed one with an offset gimbal.....
http://rvtpanet.club.fr/Articles/Liv...tete_rotor.jpg
thanks
I'v been told about this limitation. But i don't plan to market something at the moment. XWe have not this limitation in france and europe.
BTW, a rumour says that Ermie Boyette (dominator )and Dick Degraw are preparing a kind of 3 bladed rotor with jump take off capabilities... i bet they will find the right category... i bet the 3 bladed rotors offer is prone to increase.
BTW some 3 bladed gyros (lioré and la cierva) didn't have a helicopter-like cyclic control but a "teetering" 3 bladed one with an offset gimbal.....
http://rvtpanet.club.fr/Articles/Liv...tete_rotor.jpg
thanks
Last edited by zeeoo; 7th Feb 2005 at 20:57.
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what is the best helicopter in autorotation
Nick Lappos says that pilots hate high inertia rotor systems because of the slow reaction times. Whilst I am sure he is correct. I am still convinced that for the new generation of vlh machines, (especially when considering what level of experience the novice would be pilots may have), the necessity for excellent autorotational performance outweighs the downside of slow responce time. Observe Slowrotors comments. He wants low and slow. Zeoo I think seeks something similar. These single place machines are in my view what todays quad bikes are. A nice toy for not going very far in on a sunday afternoon.
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Bug,
good comparison, may i ad that the quad market is very healthy and that their usage is far beyond the simple recreationnal : all-terrain patrols, beach watch and rescue, wildlife watch, small transportation, utility vehicle, rough terrain reckon, embedded vehicle , it is simple to operate, simple to maintain and repair, a lot of peole can purchase it and even use it on the road..
I is not a land rover, but it can replace it where it can do the same job at less cost..
i like the comparison.
thanks
Victor
good comparison, may i ad that the quad market is very healthy and that their usage is far beyond the simple recreationnal : all-terrain patrols, beach watch and rescue, wildlife watch, small transportation, utility vehicle, rough terrain reckon, embedded vehicle , it is simple to operate, simple to maintain and repair, a lot of peole can purchase it and even use it on the road..
I is not a land rover, but it can replace it where it can do the same job at less cost..
i like the comparison.
thanks
Victor
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zeeoo,
It will be interesting to see how they do it. It could result in a safer gyrocopter. Hopefully, it might also be a first step in eventually getting helicopters included in the Sport Plane/pilot category.
_____________________
"BTW some 3 bladed gyros (lioré and la cierva) didn't have a helicopter-like cyclic control but a "teetering" 3 bladed one with an offset gimbal....."
Interesting. I assume from your comment and sketch that the blades have a very small offset hinge and then the hub is mounted on a gyrocopter style of gimbal. Perhaps this is why it has been mentioned that the larger gyrocopters required excessively large cyclic control forces.
I suspect that a minimal offset will result in acceptable cyclic control input forces, whereas a larger offset will result in crisper maneuvering. Pick one. The 'Sunday driver' will require both and this probably necessitates a conventional helicopter flight-control system.
To add to the subject, the following is the spider control used on the Ciarva W-11 rotor.
Dave
It will be interesting to see how they do it. It could result in a safer gyrocopter. Hopefully, it might also be a first step in eventually getting helicopters included in the Sport Plane/pilot category.
_____________________
"BTW some 3 bladed gyros (lioré and la cierva) didn't have a helicopter-like cyclic control but a "teetering" 3 bladed one with an offset gimbal....."
Interesting. I assume from your comment and sketch that the blades have a very small offset hinge and then the hub is mounted on a gyrocopter style of gimbal. Perhaps this is why it has been mentioned that the larger gyrocopters required excessively large cyclic control forces.
I suspect that a minimal offset will result in acceptable cyclic control input forces, whereas a larger offset will result in crisper maneuvering. Pick one. The 'Sunday driver' will require both and this probably necessitates a conventional helicopter flight-control system.
To add to the subject, the following is the spider control used on the Ciarva W-11 rotor.
Dave
Last edited by Dave_Jackson; 7th Feb 2005 at 23:36.
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shaun coyle said.....I'm partial to the R-44 after just over one hour...
he he...youd be suprised shaun they auto quite well.....but id rather auto a jet banger any day...
did my check on a 407 a couple of weeks ago...what a piece of grunt but it falls like a lead balloon!!
im assuming with a professional of your experience the r44 would be a snack........one day i will get to the HAI and meet all you legends i cant wait!!
he he...youd be suprised shaun they auto quite well.....but id rather auto a jet banger any day...
did my check on a 407 a couple of weeks ago...what a piece of grunt but it falls like a lead balloon!!
im assuming with a professional of your experience the r44 would be a snack........one day i will get to the HAI and meet all you legends i cant wait!!
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Le tripale:
-moyeu rotor réalisé par Joseph Gisquet (gyroclub Bois de la Pierre).
-pales réalisées par Xavier Averso.
-essais réalisés par Xavier.
-rapport Vol moteur #142 février 1998.
-moyeu rotor réalisé par Joseph Gisquet (gyroclub Bois de la Pierre).
-pales réalisées par Xavier Averso.
-essais réalisés par Xavier.
-rapport Vol moteur #142 février 1998.
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From Xavier Averso himself :
this rotor was not for a gyro use, it was a special order fom a customer.
he took 3 shortened blades (2.80m) he put on a tri-bladed hub some guys were doing, this hub had no lead-lag hinges.
results : long take off (small diameter) , high command efforts, better high speed and finesse (lower disk pitch).
he stopped the test to not damage the blades.
this rotor was not for a gyro use, it was a special order fom a customer.
he took 3 shortened blades (2.80m) he put on a tri-bladed hub some guys were doing, this hub had no lead-lag hinges.
results : long take off (small diameter) , high command efforts, better high speed and finesse (lower disk pitch).
he stopped the test to not damage the blades.
It's not just an adventure....
it's just a job!
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Gentlemen, IMHO the best helicopter in an autorotation is the one you walk away from. Practice, practice, practice.
OffshoreIgor
OffshoreIgor
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FWIW
I renewed a local requirement of a 90 day recency on the R44 today after having flown and autorotated R22, B47G and EC120 for the previous three months. It included auotorotations to the hover.
Yep, the R44 is my favourite of the four. Shallower angle, benign rotor speed control in turning descent, plenty of rotor energy left at the end of the flare and all at a pace that gave spare time for thinking.
Maybe Frank is right in saying that the R44 would make a great ab initio training machine.
Now, if we can get the cost per hour down...
I renewed a local requirement of a 90 day recency on the R44 today after having flown and autorotated R22, B47G and EC120 for the previous three months. It included auotorotations to the hover.
Yep, the R44 is my favourite of the four. Shallower angle, benign rotor speed control in turning descent, plenty of rotor energy left at the end of the flare and all at a pace that gave spare time for thinking.
Maybe Frank is right in saying that the R44 would make a great ab initio training machine.
Now, if we can get the cost per hour down...
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The 480..actually good for something!
Best autos?
Well it can't pull a limp dick out of a lard bucket or keep it's doors closed properly .....but the Enstrom 480 autos like a dream!...Lots of inertia, great controllability, easy to maintain Rrpm. I guess one could say the same for a '47 but the Enstrom gets the nod in range.
My thots anyways
Well it can't pull a limp dick out of a lard bucket or keep it's doors closed properly .....but the Enstrom 480 autos like a dream!...Lots of inertia, great controllability, easy to maintain Rrpm. I guess one could say the same for a '47 but the Enstrom gets the nod in range.
My thots anyways