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Old Feb 03, 2012, 07:14 AM
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leadfeather's Avatar
Joined May 2006
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Idea
4 bar mechanism

Here is an idea that may be helpful for bicopters/bicopter type VTOLs. Using a 4 bar mechanism for pitch control

By using a 4 bar mechanism to tilt the motors, it is possible to place the "apparent pivot point" called the "instant center" well above the copter for more effective pitch control.
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Old Feb 04, 2012, 02:52 AM
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VTOLicious's Avatar
Austria
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Interesting thoughts...sorry, but I donīt quite follow

Can you make a sketch that illustrates the applying forces and moments?

Cheers, Michael
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Old Feb 04, 2012, 02:55 AM
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interesting idea, cant wait to hear how it works in practise.
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Old Feb 04, 2012, 05:47 AM
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Quote:
Originally Posted by VTOLicious View Post
Interesting thoughts...sorry, but I donīt quite follow

Can you make a sketch that illustrates the applying forces and moments?

Cheers, Michael
The sketches below might help clear it up a little.

In interesting note is that the motor translates relative to the cg which equates to weight shift. If the side links of the 4 bar mechanism were parallel to each other, there would be no tilting of the the thrust but there would still be the weight shift component.

As drawn the mechanism gives the tilt and weight shift effects together.
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Old Feb 04, 2012, 06:36 AM
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Austria
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Quote:
As drawn the mechanism gives the tilt and weight shift effects together.
Well, your IC is the geometrical intersecion of the 2 side links. But what makes you think the whole aircraft pivots around the point what you call the "instant center"?

I donīt see any benefit...by now

Regarding the weight shift: If you donīt balance the motor-nacelle youīll always have some weight shift when its pivoting relativ to the fuselage.
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Last edited by VTOLicious; Feb 04, 2012 at 06:47 AM.
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Old Feb 04, 2012, 08:08 AM
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France
Joined Nov 2008
77 Posts
I understand the leadfeather idea, I've tried a lot of mechanism on my tricopters yaws.
The main point for our bi/tri tilt mechanism is to reduce the distance between the tilt center and the prop/motor lift center.

But the four bar mechanism could be usefull to reduce (or to "fine tune") the distance between lift axis and CG/AP of the VTOL.


(I appologize for my poor "mechanical" english)
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