Partially powered rotors from PRA magazine

JAL

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How's this, Jordan?

OH thats makes more sense to me now. The hub plates fit over the top of the rotorhead and held together by the teeterbolt, funnily enough it says that on the diagram as well. , luckily I am just pilot not a builder :)

I still can't work out how the stern tilts the rotor, where is it linked to the controls?
 

C. Beaty

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I still can't work out how the stern tilts the rotor, where is it linked to the controls?
Down at the bottom after passing through the rotorhead. The control stem is tilted in whichever direction you want to go.

The Bell-47 works the same way except it is tilted about the cyclic pitch pivots by a swashplate instead of a control stem.
 

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Mannetjie Bot

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Hi When I posted the article on the Dragonfly helicopter with the hydrogen peroxide rotor tip jets I was thinking in terms of partially powered rotors and even prerotating of the rotor. I have no idea of the cost of hydrogen peroxide and I see that a two seater has also been developed now. It just seems to be quite simple with no mechanical parts at all, Mannetjie
 

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Great photo, Chuck, thanks.

So, you've covered how the rotor is powered (planetary/differential gear system) and you've shown a diagram (and picture) of the teetering rotorhead (quite different than the usual).

What I am still missing on that rotorhead diagram is how Dick managed to change the rotor pitch to initiate the jump take-off. I see how it works in the Bell 47 photo (some collective parts below the rotorhead not shown). Nothing on the diagram seems to change the pitch. What am I missing, Chuck?

Thanks for taking the time to educate me/us !
Brian
 

phantom

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The head on de bird is a fixed spindle head, on some of my heads with collective control I have used the central yoke to do both cyclic and collective and on some I have had them separated, one up through the center and one outside and others had both done outside due to a solid shaft being used.
Norm
 

C. Beaty

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As far as I know, all of Dick’s jumpers have been 3-bladers.

As Norm says, DeBird didn’t jump.
 

birdy

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The difference between you n any other reproter CB is that you understand wot your reporting.
 

C. Beaty

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Thanks, Birdy; if you were a sweet young, female thing, I’d kiss you. But if you were, you’d run the other way.
 

C. Beaty

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Ah, Birdy and Juergen; innate poets, both.

But the meaning of the word Fknell!!!! eludes me.
 

C. Beaty

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All my conjecturing can produce is a bit of profanity, Paul and we know Mr. Bird isn’t one to indulge in profane utterances.
 

bosca

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Ahh Mr Bird..Tyre kicker ere. Rum is just a drunken sailor's drink out of Portsmouth. Must change you from the Red Mill and Milk mix to some McCallums whiskey with a touch of Red Desert. Then OL Chappy we can talk sense.
Kym.
 

kolibri282

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innate poets
My post #30 was rather a case of that queer(* sort of associations that sometimes flash through my thoughts: the combination of kiss and bird triggered a connection with that old book "To kill a (mocking)bird". As I said, that's all very strange.

I also had notions of profanity when I read birdy's post, but as you are positive that this can definitely not be the case, Chuck, I'll try to broaden my thinking.

(* I learned the word queer in 1990 when the meaning was something like "amiably quirky". To me this will never change as I will always remember the impish smile the english chap gave me when he said "Germans, what a queer race"
 
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C. Beaty

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Australians generally speak English when communicating with the outside World, Jeurgen; however, they often speak a vernacular called Strine when dealing with one another.
 

birdy

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We dont like to complicate such a simple thing as communication with stupid silent letters, multiple ways of printing the same sound or other illogical dictation laws.
 

bosca

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Mr Bird, You do come across as very intelligent and this does surprise me immensely,(I cannot believe I just said this) however OL Chappy I do request your definition and interpretation of you're last post. This is unbelievable ,I'm stunned.
So your ready for some Whiskey!!Old mate Brian agrees.!!!
OH I am quiet sober you know.
Kym.
 

C. Beaty

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We dont like to complicate such a simple thing as communication with stupid silent letters, multiple ways of printing the same sound or other illogical dictation laws.
Like site, sight, cite? Or the confusion between your and you’re?

But that’s the way English is; a bastardized mix of the Celts, Angles, Saxons, Danes, Normans, Greeks and Romans.

The French have the French Academy to keep French unadulterated but such English words as building, boxer and hamburger have crept in despite their best efforts.

(I believe this is creeping off topic)
 

Jazzenjohn

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Lets get back to parshally powered rotors then... Would it be more efficient to take some engine power, go through an alternator or generator to a motor and gearbox, and then to the rotor, or to route engine power through a prop for thrust to power the rotor with wind? It seems like you might gain some efficiency with the motor, but would the additional complexity be worth it? I had a hydraulic prerotator on my HKS gyro that I could apply power to the rotor inflight, but the output of it was so low I really couldn't detect much difference.

I get .98 for the belt .65 for the alternator .85 for the motor+ESC .92 for the reduction just for napkin figures so it winds up being a bit less than 50% efficient. The other way is even more of a guess, .75 for the prop and .40 (?) for wind to rotor for a conversion efficiency of .3 ? Sound about right?
 
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