My '74 helicopter

Jens

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Great fotos!
Looks very simple, and he only take atvantage of half of it - he still use variable pitch!?

With just a prop on the hyd motor it would be VERY simple - perfect for a hovercopter :peace:

The C-74 looks great, and is inspirering in some ways :first:
 

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brett s

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Again, you need thrust in both directions for a helicopter tail rotor.
 

RotoPlane

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If the pump was variable displacement (with a swashplate), the motor could run both directions with its speed determining the amount of thrust. A hydraulic motor with this pump can be instantly reversed, and the speed controlled, by the foot pedals......
 

C. Beaty

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I have a video tape around here somewhere of a tip jet propelled helicopter with tail rotor apparently fixed pitch and driven by a variable displacement, swash plate hydraulic pump. It would stop and run the tail rotor in reverse.

Of course, a tip jet helicopter doesn’t require much of the tail rotor.

This wasn’t a shade tree project but a main line helicopter builder; someone like Kaman.
 

brett s

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Yep, a tip jet powered helicopter is a very different animal & for the very small amount of thrust required that might make perfect sense - you could probably use an electric one too.

By the time you set up a reversing hydraulic pump setup powerful enough for a conventional helicopter I'm betting it would be significantly heavier than a plain old shaft drive & much more failure prone to boot.
 

J.C.Casabuono

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Hummm,a Vickers type pump only varies the amount of flow with the swash plate,you need some valve to invert the rotation of the hydraulic motor.
 

C. Beaty

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Everything eventually finds its place in this world.

Where would bulldozers and backhoes be without hydraulics?

But even on automobiles, when and if the new 42 volt electric standard becomes reality, hydraulic power steering will fade into the past to be replaced by electric power steering.
 

Scary Gary

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Hay Beaty !
Any time I think I may have a brain in my head and just a tad of intelligents all I have to do is go on here and see something like your 74 helo and I'm back in the corner with my dunce hat on .
That is so cool and so impressive .
I love this forum .
 

Alan_Cheatham

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Great fotos!
Looks very simple, and he only take atvantage of half of it - he still use variable pitch!?
Variable pitch gives instant thrust change where there will be a delay with variable speed as the tail rotor accelerates or decelerates. Having flown fixed pitch and collective pitch RC helicopters I can tell you there is a big difference in the controllability of the two. Many times the simplest mechanical solution is not the best answer to the problem, especially where pilot control feel is involved.
 

Jens

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Both directions..!

Both directions..!

Really - how much and how often do a tail rotor push in the wrong direction...!

It can fly in autorotation with a dead engine - and dead tail rotor.
"when descending at a low power setting" - brett said. But if there is power on rotor, it is already trying to go in the wrong direction.
And you also have forward speed..!
How come that you need a tail rotor to push it further in the wrong direction?
It must be in some special manuveres - or very fast and agile manuvers?

I can only think of its usefullnes when you have a strong side wind.
And even here, I guess, you could live without it - if you had to.

With my current understanding it looks as a fair or even a good and workable solution for prototypes and homebuild - and perfect for my hovercopter :yo:
 

brett s

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Why don't you actually fly one & find out for yourself?

You sure don't listen to any of us who have!
 

birdy

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CB, how dose a all expenses payed holiday to central OZ take ya?? ;)
You could finish this machine i started, and by the way things are go'n now, ill never get back to. :(
 

C. Beaty

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Birdy, what you really need is a lightweight helicopter fitted with a reliable engine. Not that there seems to be a reliability problem with the MZ engine but some people want nothing to do with 2-strokes.

How about a Mosquito with a turbine or perhaps one with a Honda/Suzuki/Yamaha 4-stroke outboard if you need better endurance?

An outboard engine would be a good fit for a Mosquito since the layout favors a vertical crankshaft.
 

Rotor Rooter

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Really - how much and how often do a tail rotor push in the wrong direction...!
They're always pushing in the wrong direction.

They should be pushing up like their respectable big brothers do. :D


Dave
 

birdy

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Birdy, what you really need is a lightweight helicopter fitted with a reliable engine.
If thats wot i needed CB, id already have one.
And a spare in the shed. :)

Birdy, what helicopter project have you started, or is it another gyro?
A partial powered, true VTO and land machine with full time collective. ;)
 

birdy

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If a heli could do better Misfit, id have one.
Its that simple.
The cost difference is only a bonus.
Where do you think id be now, if i was ina R22 the other day, wen the throttle cable failed??

Iv been in plenty of R22s, 47s, 300s, and nuthn gives more pice of mind than the powerless abilities of a gyro.
And nun of the helies have anythn over a good gyro from a mustern perspective, cept the VTO ability. And the cost difference wouldnt make up for that.
 
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