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Old Nov 19, 2014, 12:34 PM
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Hi Tom that's great can you give a close up of the head? I think I have a set of AJ 450 blades. I would like to give it a try, did you use any tip weights? Its amazing you had success on the first try. Our weather is lousy at the moment so I have a bit of time to get one together again regards
Kevin
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Old Nov 19, 2014, 03:43 PM
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Kevin the 0.8mm thick plate is 25 mm wide and 100 mm long ,the blade bolt holes are 35 mm from the plate center.
Taking in to account the up elevator needed the estamated rotor trim angle would be 9 -10 degrees with the elevator at zero.
This data applies to a model with an AUW in the range of 15-17oz .
The experiment would I think be best done with a dual axis head and the model initially flown with three blades , then if the three blade area can be achieved with two blades its a fair chance the model will fly with minimal trim adjustment required, (perhaps within 10% would be OK).
The model flown today was a first try and I cannot claim any of the parameters are optimal but the model flew very much the same as it did with the shorter three blade set, possibly a little more sensitive in roll.
The blades were not corrected other than each having the same weight, so further advantage might me gained by optimizing blade cog that doubles up as tip weight .
I got the impression that play in the servo and head could be more detrimental to spin up and best efficiency than it would with three blades.
I found a more power was needed to get the model away but after that the normal cruise setting was sufficient to maintain a steady and moderate speed .
Power off descents and high alpha were no problem , but it did take longer to achieve head speed in the near calm conditions.
Perhaps this is the wrong thread to discuss this if Mickey would prefer we took it over to the CF thread perhaps he could give us a nod.

Tom.
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Old Nov 19, 2014, 06:58 PM
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Thanks Tom, duly noted, thanks for the info
Kevin
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Old Feb 08, 2015, 06:16 AM
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Mickey,

1. What is the best "modern" proven Gyrocopter rotor head design for a 3 meter rotor?
2. Ideal rotor load
3. Thrustline above or below V CG
4. Tail dihedral or not
5. Wood good enough for Blade construction?
6 Clark Y or Bensen G3 or NACA 8-12-H

Thanks ahead of your response
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Old Feb 08, 2015, 07:29 AM
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Originally Posted by At Yer Six View Post
Mickey,

1. What is the best "modern" proven Gyrocopter rotor head design for a 3 meter rotor?
2. Ideal rotor load
3. Thrustline above or below V CG
4. Tail dihedral or not
5. Wood good enough for Blade construction?
6 Clark Y or Bensen G3 or NACA 8-12-H

Thanks ahead of your response
Best,Ideal are tough requirements.
3 meter radius or 3 meter diameter? A flexy tilt axis head seems out of the question.
Best for what? Easy of construction? Cost? Maintainability? Most scale looking? What application?
Same questions about rotor load. Ideal is 0, except for teetering rotor where there would be no control power. Of course if you are designing a short duration model to take pictures over turbulent air over a forest fire, then loading might need to be higher.
Depends on the application. If I were designing a big model like this, perhaps for a commercial or uav application and cost were not a big deal I'd start with a big 3 -4 bladed helicopter head and use a 3 axis gyro.
There are certainly some big models this size that use a home made teetering rotor, but I wouldn't go that direction as the control power on the teetering rotors is always iffy.
Thrust line only matters with teetering rotors where you stand a chance of pushover negative G's. With a semi-rigid rotor the thrustline almost won't matter.
Tail dihedral is really misunderstood, not important with a semi-rigid head.
Wood blades might be ok if various kinds of woods are laminated and the CG is corrected. Root stresses will be high so some care might be needed. Unless the blades are carefully made of some kind of composite to be very stiff in twisting a nearly symmetrical section will be needed, otherwise blade twist on a 1.5 meter blade will likely make things challenging.


Sorry to be so vague, but you will have to narrow down the goals for the aircraft mission before "best" and "ideal" can be applied.
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Old Feb 08, 2015, 10:36 AM
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Originally Posted by mnowell129 View Post
Best,Ideal are tough requirements.
3 meter radius or 3 meter diameter? A flexy tilt axis head seems out of the question.
Best for what? Easy of construction? Cost? Maintainability? Most scale looking? What application?
Same questions about rotor load. Ideal is 0, except for teetering rotor where there would be no control power. Of course if you are designing a short duration model to take pictures over turbulent air over a forest fire, then loading might need to be higher.
Depends on the application. If I were designing a big model like this, perhaps for a commercial or uav application and cost were not a big deal I'd start with a big 3 -4 bladed helicopter head and use a 3 axis gyro.
There are certainly some big models this size that use a home made teetering rotor, but I wouldn't go that direction as the control power on the teetering rotors is always iffy.
Thrust line only matters with teetering rotors where you stand a chance of pushover negative G's. With a semi-rigid rotor the thrustline almost won't matter.
Tail dihedral is really misunderstood, not important with a semi-rigid head.
Wood blades might be ok if various kinds of woods are laminated and the CG is corrected. Root stresses will be high so some care might be needed. Unless the blades are carefully made of some kind of composite to be very stiff in twisting a nearly symmetrical section will be needed, otherwise blade twist on a 1.5 meter blade will likely make things challenging.


Sorry to be so vague, but you will have to narrow down the goals for the aircraft mission before "best" and "ideal" can be applied.
Fair enough, excuse my weak and vague question.


Ideal Rotor Head for 3 meter diameter Gyrocopter Pusher, although I really prefer a tractor for clean air reasons.
General "utility" UAV purpose including maping. I do have CNC equipment so I build it right.
I can build or purchase a multiblade rotor head 3-4 or even 5 blade but, If I use 120 degree CCPM for cyclic, do I set the pitch fixed at 8-? degrees blade angle or use full collective. If I did this, am I now using a Heli with a pusher or tractor?. Wouldn't this defeat the conservation of energy advantage of the GyroCopter.
Blades, I can build molds once I know the correct profile and I can use composites if/where required.
I understand, that a substantial horizontal tail is desirable to resist PIO

I look forward to your thoughts.

Thanks
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Old Feb 08, 2015, 04:40 PM
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Originally Posted by At Yer Six View Post
Fair enough, excuse my weak and vague question.


Ideal Rotor Head for 3 meter diameter Gyrocopter Pusher, although I really prefer a tractor for clean air reasons.
General "utility" UAV purpose including maping. I do have CNC equipment so I build it right.
I can build or purchase a multiblade rotor head 3-4 or even 5 blade but, If I use 120 degree CCPM for cyclic, do I set the pitch fixed at 8-? degrees blade angle or use full collective. If I did this, am I now using a Heli with a pusher or tractor?. Wouldn't this defeat the conservation of energy advantage of the GyroCopter.
Blades, I can build molds once I know the correct profile and I can use composites if/where required.
I understand, that a substantial horizontal tail is desirable to resist PIO

I look forward to your thoughts.

Thanks
Use the heli head, but not the power train. Use much bigger blades than the heli would use to get the efficiency up.
I would use collective to make the rotor speed up when taxing faster, then move to the correct pitch for flight.
Tractor propeller will give you the most rotor clearance.
Horizontal tail not needed with gyro. Or properly designed rotor. PIO is only a problem with a control system with sluggish response, like a teetering sytem.
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Old Feb 08, 2015, 07:01 PM
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Originally Posted by mnowell129 View Post
Use the heli head, but not the power train. Use much bigger blades than the heli would use to get the efficiency up.
I would use collective to make the rotor speed up when taxing faster, then move to the correct pitch for flight.
Tractor propeller will give you the most rotor clearance.
Horizontal tail not needed with gyro. Or properly designed rotor. PIO is only a problem with a control system with sluggish response, like a teetering sytem.
What shaft offset angle would you recommend 17 degrees?
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Old Feb 08, 2015, 08:29 PM
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Originally Posted by RYBAT View Post
What shaft offset angle would you recommend 17 degrees?
18 is what I used on my smaller models so they would take off and land without wild pitch changes, level with the landing gear. They would basically just rise off when the speed got right.
I suspect as the efficiency goes up with size a lower angle will be optimum. I'd build a bare bones stick model first with some kind of mast rake adjustment. Then when all the angles get tuned, build the real one. Same process I used.
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Old Feb 08, 2015, 08:53 PM
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Originally Posted by mnowell129 View Post
18 is what I used on my smaller models so they would take off and land without wild pitch changes, level with the landing gear. They would basically just rise off when the speed got right.
I suspect as the efficiency goes up with size a lower angle will be optimum. I'd build a bare bones stick model first with some kind of mast rake adjustment. Then when all the angles get tuned, build the real one. Same process I used.
Great, Good idea and very do able
Thanks for yer time.
Could you post a few pics?
I'm sure others would enjoy seeing them too!
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Old Feb 08, 2015, 09:46 PM
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Ditto, Rybat beat me to it

Thanks for the info. Since I'll be using CCPM no need for tilt mechanism. I'll use the main gear for the pre-rotator and the one way bearing will allow for the free rotation after Vto head speed is reached. Just need to cut down a 12 mm shaft and make some new bearing blocks
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Last edited by At Yer Six; Feb 08, 2015 at 10:27 PM.
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