What some (or many or all) gyro guys going through and what a reward at the end !

Aerofoam

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A quick search found 2"OD Ti tubing at .035" wall for $650 per 8' section......
3 suppliers had no results for .065" wall....
Unless I find it as scrap, that is out for me!
 

MikeBoyette

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Use 2" x .065" chromo, flexible and strong. Tall tails are mounted ina way that is not going to triangulate the mast but even so a tall tail must add some damping to the otherwise flexibity of the mast. In Chuck Beattys words a mast can't be too flexible.

wolfy
Very true. I remember him saying if you could get away with a mast made completely of rubber it would be amazing. As for the tail flexing that’s why there is only one bolt through the mount at the top and it’s not tightened completely down so it can move.
 

wolfy

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Very true. I remember him saying if you could get away with a mast made completely of rubber it would be amazing. As for the tail flexing that’s why there is only one bolt through the mount at the top and it’s not tightened completely down so it can move.
True but with the tail attached to the mast the mast must move the tail whenever it moves, so just by having to move the tail must add some damping/stiffening to the mast.

wolfy
 

Georgi

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Sparrowhawk autogyro chose this tall tail attachment configuration. I've never flown in them. How smooth (or not) are they? Thank you.
 

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MikeBoyette

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True but with the tail attached to the mast the mast must move the tail whenever it moves, so just by having to move the tail must add some damping/stiffening to the mast.

wolfy
Not enough to affect the masts ability to dampen the natural two per rev of a two blades see saw rotor system. Oh by the way the bigger you scale up such a system the worse the two per rev gets. This is why in my opinion Bell changed everything they have to a four bladed system.
 

bell206

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Bell changed from 2 blades for more speed, certainly not for simplicity. I owned a couple of Bell Longrangers and they were smoother than any multibladed ship I flew in. The Longranger has a nodal beam ( like a leaf spring) that the transmision and mast was mounted to. It would absorb the vibration and isolate the cabin.
The multibladed ships would trade a faint 2 per rev for a fast 3, 4 or 5 per rev and a host of other quirks.
I believe the Bell 206 Jetranger was and is the best all around helicopter ever made.
Hence my moniker.
Not enough to affect the masts ability to dampen the natural two per rev of a two blades see saw rotor system. Oh by the way the bigger you scale up such a system the worse the two per rev gets. This is why in my opinion Bell changed everything they have to a four bladed system.
 

WaspAir

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My Bell 47, at more than twice the LSA weight limit, is smoother than any teetering gyro I've encountered. Bell never would have sold over 13,000 47s and 206s across many decades and against stiff competition if the vibration was problematic.
 
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bell206

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Not enough to affect the masts ability to dampen the natural two per rev of a two blades see saw rotor system. Oh by the way the bigger you scale up such a system the worse the two per rev gets. This is why in my opinion Bell changed everything they have to a four bladed system.
Mike ,
I think Bell reached the limit that could be done with a 2 bladed system in their new Bell 505 2 bladed replacement of the Jetranger. It cruises at 150 mph smoothly. But their 4 bladed AH1-Z Viper does 200 knots fast cruise,
The AH1-G Cobra would do 200 in a dive but after you pulled out you would just take it back and get another one cause that one shook so bad something had to be wrong with it. Don't ask me how I know.
 

MikeBoyette

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The opinion reached by me was based on what Chuck Beaty taught me. He said a two bladed rotor will always shake. Bell mounted the transmission in rubber to try to eliminate it. From what I understand that’s why RAF made their mast mounted in rubber. Chuck said the blades always take a hit from incoming air when at the 9 and 3 o’clock position. That is what causes the two per rev. Systems more than two blades don’t suffer this problem.
 

WaspAir

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My 47 engine has a vertical crankshaft with clutch/tranny/mast/head stacked above it. It has a soft mount way down at the bottom of the engine. Any play between engine and transmission would be unwelcome, so the tranny is probably not the best place to start softening for that configuration.
 

bell206

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The opinion reached by me was based on what Chuck Beaty taught me. He said a two bladed rotor will always shake. Bell mounted the transmission in rubber to try to eliminate it. From what I understand that’s why RAF made their mast mounted in rubber. Chuck said the blades always take a hit from incoming air when at the 9 and 3 o’clock position. That is what causes the two per rev. Systems more than two blades don’t suffer this problem.
I guess its a matter of preference, do you like your vibrator on low or high?
 

MikeBoyette

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My 47 engine has a vertical crankshaft with clutch/tranny/mast/head stacked above it. It has a soft mount way down at the bottom of the engine. Any play between engine and transmission would be unwelcome, so the tranny is probably not the best place to start softening for that configuration.
Well I stand corrected. I was just going by what he told me. He also said the 47’s with wood blades were smoother. He loved wood blades.
 

okikuma

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Not enough to affect the masts ability to dampen the natural two per rev of a two blades see saw rotor system. Oh by the way the bigger you scale up such a system the worse the two per rev gets. This is why in my opinion Bell changed everything they have to a four bladed system.
Arthur Young was the developer of the two blade, semi-rigid, teetering, rotor system and had an exclusive rights agreement with Bell whereas the company could not use any other type of rotor system as long as Arthur was alive. As told to me by a former Bell Helicopter engineer, Arthur was paid a "royalty fee" for every Bell helicopter that was built using his rotor system. When Arthur passed away, Bell immediately went forward with fully articulating rotor systems.

Nodal beam and relatively soft Lord type isolator mounts are two examples that Bell used to help absorb the 2/rev vibration.

Watch the following video on how Wagtails answer to help absorb the 2/rev vibration of their rotor system on the Kriek II tractor gyroplane. As the gyroplane is taxing over uneven ground, one can see (starting at 0:25 seconds) and during flight (starting at 0:45, and again at 1:25 seconds) how the rotor mast is allowed to move about and track to absorb those 2/rev vibrations. Focus one's vision at the rotor mast in between both instrument panels.


With fully articulated rotor systems. the vibration is from a mismatch of individual rotor blade weights and blade tracking.

Wayne
 
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bell206

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Arthur Young was the developer of the two blade, semi-rigid, teetering, rotor system and had an exclusive rights agreement with Bell whereas the company could not use any other type of rotor system as long as Arthur was alive. As told to me by a former Bell Helicopter engineer, Arthur was paid a "royalty fee" for every Bell helicopter that was built using his rotor system. When Arthur passed away, Bell immediately went forward with fully articulating rotor systems.

Nodal beam and relatively soft Lord type isolator mounts are two examples that Bell used to help absorb the 2/rev vibration.

Watch the following video on how Wagtails answer to help absorb the 2/rev vibration of their rotor system on the Kriek II tractor gyroplane. As the gyroplane is taxing over uneven ground, one can see (starting at 0:25 seconds) and during flight (starting at 0:45, and again at 1:25 seconds) how the rotor mast is allowed to move about and track to absorb those 2/rev vibrations. Focus one's vision at the rotor mast in between both instrument panels.


With fully articulated rotor systems. the vibration is from a mismatch of individual rotor blade weights and blade tracking.

Wayne
Wayne,
I think the deal Young had with Bell was one of those urban legends told by Bell employees to each other, but you and I will never know.
Young died about 30 yrs ago and if Bell wanted too they would have produced one years ago.
From an operator standpoint you could hanger three Longrangers in the hanger space of one three bladed equal passenger carrying machine like an Astar. Simplicity of maintenance on the two bladed machines compared to the expensive complexity of the multibladed was a big factor.
The European multibladed competition to Bell maintenance costs were so high that we joked that they should just give the operator the helicopter free so they could buy the expensive parts needed to keep them flying. I should know I owned one, but thats another story.
Robinson has been pretty successful with two.
There is some truth in what Mike is saying , but I enjoy pulling his chain a little.
 

Eric S

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The opinion reached by me was based on what Chuck Beaty taught me. He said a two bladed rotor will always shake. Bell mounted the transmission in rubber to try to eliminate it. From what I understand that’s why RAF made their mast mounted in rubber. Chuck said the blades always take a hit from incoming air when at the 9 and 3 o’clock position. That is what causes the two per rev. Systems more than two blades don’t suffer this problem.
I had a RAF with Sparrowhawk mod for a while with the "magic" bushing in the upper mast. You could look up in flight and see the mast moving slightly, but there was no stick shake. Everything else in gyros seems to get copied. It surprises me no one copied the RAF magic stick shake solution.
 

bell206

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I had a RAF with Sparrowhawk mod for a while with the "magic" bushing in the upper mast. You could look up in flight and see the mast moving slightly, but there was no stick shake. Everything else in gyros seems to get copied. It surprises me no one copied the RAF magic stick shake solution.
Anybody have a picture of the magic bushing Eric describes?
 
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