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HomeScale✈️AircraftScale HeliScale Helicopter Main Discussion › Vario 3 Blade head
07-17-2006 07:02 PM  14 years ago
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The_Dave

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Las Vegas / Pahrump, Nevada

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Vario 3 Blade head
OK Scale experts.....I know this has been asked 4000 times before but I hate doing searches (call me lazy!)but I have a question about 3 blade heads.

I have a benzine trainer that will be going in a Astar and I have the 3 blade head for it. I am a little light on instructions and diagrams as my buddy Mark who gave it to me is not around to answer questions....

So, I have set up and flown 4 blade heads with no problems but they are easy as the phasing is on the 90's. The 3 blade is 120 degrees and I am sure some black magic voodoo has to take place on the swash.

I need to know the proper phasing, and how to achive it. It would also be helpful if you can offer the correct pitch for hovering.

Any and all help is most welcome....
Mark McAlpine - 2005 - We will never forget.
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07-17-2006 07:22 PM  14 years ago
modtron

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Oxford. UK

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Hi Dave,
I use both the Vario 3 & 4 blade systems. Both are set up exactly the same way with 90' phasing. As for pitch settings, I use -2 at the low end, + 4 to 5 in the hover and +8 to 9 at the top.

Modtron
Oxford UK
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07-17-2006 07:32 PM  14 years ago
The_Dave

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~
Thanks for the quick reply...

Ok, I will try to understand what you are saying...

Your phasing is on the 90's, but the blades themselves are 120 degrees apart...how do you accomplish the 90 degree phasing you talk about?

Assume that one blade (lets call it the master blade) is directly over the tail boom. You give forward cyclic, what movement does the blade make? On a 4 blade head it would not move at all (or very little)but again everything on the 4 blade is on the 90.

I know that procession will remail constant, and that 90 will always be 90...I am stuck on how to factor in the 120 of a 3 blade head.
Mark McAlpine - 2005 - We will never forget.
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07-17-2006 07:45 PM  14 years ago
Notar (RIP)

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Taxachussetts

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All heads phase left or right 45degrees.If you have to do it manually by rotating the swash lock, move it so the rods at are a 45 degree angle behind the blade leading edge. Same applies to the blade over the boom. With one blade over the boom, and you give forward cyclic, the blade should not move. If it does, move the swash lock slightly until it barely moves at all, or not at all.
This is the same with 3,4,5,6 blade heads.
joe
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07-18-2006 07:56 PM  14 years ago
kangarooster

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Orlando Fl-USA

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Do flybar heads phase shift the same as non-flybar heads?
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07-18-2006 09:39 PM  14 years ago
modtron

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Oxford. UK

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Physics dictate that the law of any gyro will result as follows...

A given input into a spinning gryo, will result in the output being at 90 degrees after the input in the direction of rotation.

If you consider that a flybar model effectively has 2 gyro's (spinning masses).

1 - the flybar
2 - the rotor disk

If you tilt the swashplate forwards and freeze it there, the following happens every rotation.

The action of the first gyro (flybar) is for the paddles to change their angle as they rotate. So when the swashplate is tilted forwards, the flybar paddles will look as though they will tilt the flybar to one side. This is the input, but the resultant force of the output will happens 90 degrees later in rotation, so tilting the flybar forwards

Now consider the action of the flybar on the rotor disk. The blades are now going through the same movements as that of the paddles, but again the gyro force will output 90 degrees after, in the direction of rotation, so tilting them forwards.

It's easy to see each phase of the action as you slowly rotate the rotor head, but you must always remmember that this happening every time the rotor disk rotates.

To fly a model, you don't really need to understand about gyroscopic pressession. All you need to know is that when you push forwards, thats the way it goes.

Modtron
Oxford UK
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