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Old Mar 26, 2010, 07:09 AM
Mickey from Orlando. Really.
Joined Nov 2004
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Quote:
Originally Posted by Boneswamped View Post
Thanks for the input Mickey,
-I agree with you on the collective function, good point. It shouldn't be too difficult to setup the way you mentioned with some simple radio mixing.
-Do you think the three blade swash set-up would be controllable without a flybarless control system?
Yes, you may have to play around with tip weight, but especially this large I don't think it will be a problem.
Quote:
Originally Posted by Boneswamped View Post
-If the head were mounted with enough aft tilt for spin up(as in a roll only setup), utilizing swash function for cyclic functions; do you feel it would still need collective?
Nope, BEGi and G3PO do it this way just fine.
Quote:
Originally Posted by Boneswamped View Post
-I'm leaning towards a rigid rotor setup with lead/lag(Accomplished with the single blade mounting bolt) and flapping occuring in the root of the blade mounting(most likely with a small segment of glass fiber between the blade and the grip), of course feathering would occur at the blade grip.
I wouldn't do this myself. The glass will flex in torsion and let the blade wander around. I wouldn't worry about flapping, you don't need it with feathering. I have a metal brace on my heads to STOP them from flapping.

Quote:
Originally Posted by Boneswamped View Post
I think it could get away with this because the rotors were spun beyond autorotational RPM with the tip jets.
You could too if you did pre-spin.
Quote:
Originally Posted by Boneswamped View Post
Your experience with this type of setup is invaluable to this project, so I'll appologize in advance for the many ignorant questions to follow.
Happy to help. Glad someone else is trying a swash/feathering setup. Be warned that once you do you may like it.
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Old Mar 26, 2010, 06:06 PM
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DeRidder LA.
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3-blade head

Hey guys,
As I suspected the true scale rotor head would be my first compromise in the design phase. This is because the full scale aircraft utilized a very complicated system of ductwork, and fuel lines to supply the tipjets with the enormous quantities of fuel they consumed in the hover phase. It pumped compressed air to the tips which was then mixed with the fuel to power the tip jets. The jets were essentially ram-jets. I'm not going to recreate the actual rotor head because I'm not capable of the machining work that's required. Instead, I'll use a commercially available 3-blade heli head and swash system.

I will most likely include a prerotation system. I think the pre-rotator will use a brushless motor with a clutch bell that doesn't engage until the motor reaches high RPM. This would solve brushless start-up issues, and allow a soft start for the blades.

Regards,
-Mike
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Old Mar 26, 2010, 06:41 PM
Mickey from Orlando. Really.
Joined Nov 2004
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Quote:
Originally Posted by Boneswamped View Post
I think the pre-rotator will use a brushless motor with a clutch bell that doesn't engage until the motor reaches high RPM. This would solve brushless start-up issues, and allow a soft start for the blades.
I wouldn't go to the trouble if it was me, because 1) electric motors make the max torque at low rpm anyway. 2) model heli's use brushless motors geared for insane rpms and startup just fine, especially with soft start ESC's 3) With collective you can set the blades to flat pitch for pre-spin, so there is very little drag involved, just inertia.
I tried brushless pre-spin on mine, didn't make that much difference because the pre-spin time is only a few seconds and even a brushed motor didn't have enough time to get hot. Basically you can abuse the heck out of the motor for 5 seconds without much regard for it. The motors seem like they fail when they heat for a long time and can't get rid of the heat, so it builds up inside. I think I calculated that I'm making 20 or 25 watts out of the IPS motor for prespin and it's only rated for 15, I haven't burned one up in hundreds of starts.

What head is that in the picture?
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Old Mar 26, 2010, 06:49 PM
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Good point Mickey, that's exactly why I'm seeking your input on this project. Brushed it is.....cheaper anyway, which is always good.

The rotor head pictured is a Century DIAMOND 3-BLADE 30-50 SIZE ROTOR HEAD. Available from Heli-World.

Thanks for the help. I'm open to any ideas and suggestions for sure.

Regards,
-Mike
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Old Mar 29, 2010, 02:19 AM
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This is a difficult aircraft to find photos of, I'm finding the same few pics regardless of the website. This picture is one of the captured aircraft that was brought to the U.S. during operation paperclip.

Any new information not already in this thread would be appreciated.

-Mike
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Old Mar 29, 2010, 12:06 PM
It was a GLITCH! Honestly!
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Stourport on Severn ,Worcestershire, United Kingdom
Joined Dec 2007
4,875 Posts
Mike,
I have searched hard and like you the same photos keep cropping up, I think the picture John posted should be more than enough to get something very close. The rest you could get from the different photos and a bit of 'guesstimation'
If you look to long you will lose interest and we want to see a BIP, the undercarraige looks interesting, steel or Alloy tube? I have been using some 1/2 aircraft grade alloy tube on a project and for the life of me I cannot tig weld it
Steel tube would be my choice as its easy to weld or braze...then again there is carbon but at a cost.

Regards Rich
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Old Mar 29, 2010, 02:04 PM
flingawing
Joined Jan 2005
58 Posts
Hello Mike,

It's a pusher, might be easier to build? See attached photos.

Joel
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Old Mar 29, 2010, 05:27 PM
Suck it and see
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Cromer, North Norfolk Coast, UK
Joined Aug 2008
525 Posts
Not a bad idea Joel, but I'm not sure what Mike thinks about autogyros with wings.
John
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Old Mar 29, 2010, 05:38 PM
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Hi Joel,
I appreciate the photos you posted. I'm set on the WNF 342 though. Maybe someone else will take on the project you suggested.

I've found around 20 or so photographs of the Doblhoff, the problem is; every link I find has the same poor quality images. I've completely failed at finding any line drawings of the aircraft. As Rich, and others have stated, I should be able to get close with what I have. The good thing is nobody will be able to dispute the accuracy of my interpretation.

Regards,
-Mike
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Old Mar 30, 2010, 04:57 AM
What could possibly go wrong!!
In Bedfordshire, UK.
Joined Oct 2008
662 Posts
Hi Mike,
You may already have these pics but here they are anyway. Fuselage length is 19ft. 11inches. The very small front wheel looks a problem if you want to be scale-ish and I would imagine you will need to include some wire bracing on the twin booms to keep it rigid. Good luck on this stealth autogyro project.

Regards Chas
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Old Mar 30, 2010, 05:05 PM
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Thanks Chas,
The line drawings and photos you posted are the best I've seen yet. Very helpful. You Rock!

Regards,
-Mike
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Old Mar 30, 2010, 05:54 PM
AND FOR MY NEXT TRICK....!
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Omaha Millard, Nebraska, United States
Joined Sep 2004
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Mike,
Are you going to be spinning clockwise? What are your materials going to be.....on the landing gear and ect.
Joe
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Old Mar 30, 2010, 07:46 PM
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Quote:
Originally Posted by jodini View Post
Mike,
Are you going to be spinning clockwise? What are your materials going to be.....on the landing gear and ect.
Joe
Hi Joe,
It will spin CCW like the original. The airframe structure, as it's planned in my head for now, will probably be ply and balsa. I have considered a complete tube structure with fabric covering, and I'm still undecided. The gear will be tubing, still haven't decided the material since I need to do some testing. I'm practicing my small tubing welding techniques, but it's more difficult than I anticipated.

I'm pretty excited about this build. I hope to keep the specialized building techniques to a minimum in the event others want to duplicate the work later.

Regards,
-Mike

p.s. I am starting a smaller version for testing. It will be from recycled gyro's in my hangar.
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Old Mar 30, 2010, 11:35 PM
AND FOR MY NEXT TRICK....!
jodini's Avatar
Omaha Millard, Nebraska, United States
Joined Sep 2004
4,062 Posts
Sorry...I was looking at the Buhl Autogyro. It was clockwise.

Well look foward to what you come up with!
Joe
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Old Mar 31, 2010, 05:43 AM
What could possibly go wrong!!
In Bedfordshire, UK.
Joined Oct 2008
662 Posts
Hi Mike,

You could try silver soldered brass tube with a fabric heat shrink, carbon would of course be lighter but it is brittle. I think I would go for the light ply and balsa option. (its easy to repair)
Just for interest I read that the WNF 342 V4:
2 seater
engine Sh 14A
135 horsepower
rotor dia 32ft. 3 ins.
empty weight 435Kg
loaded weight 635Kg

Regards Chas
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