Osprey Madness

[Scotaidh]

Whilst looking at SeaDude's Osprey build, my mind took a left turn to wonder what folks have Whiffed from that animal.  I was thinking in terms of Rotodyning it - make the wing-tip engines fixed with shorter blades and adding a Chinook rear tower to it with suitable blades ...

then I wondered if how many blades would be enough ...  would three work?  What about two, like from a Cobra?

if not then ... add a second three-blade above it? 

What about counter-rotating blades - would that even work on a Rotodyne?

[kerick]

There was some engineering reason why the Osprey had three rotor blades. I'll have to look it up later. Of course in whiff world........
Then if you add a Chinook style back end you could just use another Osprey rotor. With a nice Cheyenne style pusher prop.

[PR19_Kit]

The Rotodyne doesn't need a counter-rotating rotor as it has no torque reaction. Them tip jets just squirt the rotor round without any reaction on the airframe.

Of course there's northing stopping you doing that with one, in fact I have one just like that home. It was donated to us on the SIG stand one y7ear, and I'm still its keeper.

[jcf]

The Rotodyne is essentially an autogiro, the main rotor is unpowered in forward flight. The tipjets are only used for takeoff and landing, the rest of the time the rotor functions solely as a free rotary wing.
A coaxial rotor setup wouldn't work.

However if you make it into a "compound"
helicopter, that's a different kettle of fish.
There was an actual Kamov concept many decades back that added a coaxial rotor system; engine, transmission and rotors,
to an Li-2 to produce a compound helicopter.

 


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[chrisonord]

I put the wings and engines from an E-2C on one, and s tall T tail. It's job was to be a STOL light transport, with carrier capability, so could be used for COD duties, and dropping seal teams off. As usual, when I put it on here it got ridiculed by the few that don't get what if.

[PR19_Kit]

.........when I put it on here it got ridiculed by the few that don't get what if.

What were THEY doing on here anyway? I hope we slung the ratbags off!

[Stan in YUL]

A two-blade rotor is indicative of a semi-rigid rotor head while the three or four blade is for a full articulated rotor head. In short it's a stability thing that allows for greater speed and engine torque utilization.

[chrisonord]

.........when I put it on here it got ridiculed by the few that don't get what if.

What were THEY doing on here anyway? I hope we slung the ratbags off!

If I remember correctly, it was several of the forums "established" members.

[Scotaidh]

No, I know the Rotodyne rotor was powered, I was just wondering how much more lift it'd have if there was a second identical rotor above that, going the other way 'round ... There's a wee voice in my head saying that if it worked at all then it would be less than twice as much, but more than 1.5 times the original ... and I don't know if it'd be worth the effort of making it.  I am no mathematician.

The Rotodyne pretty much had to have an even number of rotor blades to keep things "simple" gubbins-wise - you know, one Eland sending HP air to blades 1 & 3, the other Eland handling blades 2 & 4 .. !  So two blades would work, four did, six & etc weren't done.  Three blades, like wot the Chinook has would only work if you had two of them for 6 blades total - then you could have one Eland powering each rotor - until you lost the wrong one of each, which would be awkward.

The easiest way to add a top rotor to the Osprey would be to nick the rear rotor tower off a Chinook and dob it on - but three blades won't work the Rotodyne way, so lacking a four-blader just stacking on the Chinook's front rotor - with tip-jet added to all blades. 

It would look kinda weird, I'll grant you,

[kerick]

We love weird!

[PR19_Kit]

The Rotodyne pretty much had to have an even number of rotor blades to keep things "simple" gubbins-wise - you know, one Eland sending HP air to blades 1 & 3, the other Eland handling blades 2 & 4 .. !  So two blades would work, four did, six & etc weren't done.  Three blades, like wot the Chinook has would only work if you had two of them for 6 blades total - then you could have one Eland powering each rotor - until you lost the wrong one of each, which would be awkward.

Nope, it didn't.

The Elands fed compressed air to a ring manifold around the rotor hub and that fed all four tip jets equally. The fuel was piped along the blades as well and ignited in the tip jets when it got there. It could possibly have worked with any number of blades, 2 or more anyway.

[zenrat]

What Kit said.

My Tinydyne has three blades and the Maxidyne will have five.

[Scotaidh]

Hmmm - it seems my research is at least suspect if not downright wrong.  I'll have to find it again.

[Scotaidh]

Kit - what's your source for that?  I don't have any personal knowledge of this bird, only what I can find on the internet.  I'm not saying you are wrong - please don't think that.  I'd just like to know your source ... I hate being wrong, myself.

Wikipedia - dubious source at at best, I know - says each Eland fed only two rotors
https://en.wikipedia.org/wiki/Fairey_Rotodyne

and so does Aviastar
https://www.aviastar.org/helicopters_eng/fairey_rotodyne.php

History.net also says this.
https://www.historynet.com/fairey-rotodyne-an-ingenious-blend-of-airplane-and-helicopter/

[PR19_Kit]

The book on the 'dyne by David Gibbings, pu8blished by the History Press.

It's called 'Fairey Rotodyne', catchy title, eh?