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01-26-2007 07:58 PM  10 years agoPost 1
lowtone20hz

rrNovice

E. Falmouth, MA

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I have recently revisited Radd's to work on nose-in orientation. While working on tilting the swash I have noticed that the rotor disc doesn't point (that section dips and is the lowest point) exactly in the direction I'm giving it. It seems to be off a few degrees. See picture below for which direction is pointing where. Is this normal and part of the mixing or do I have a problem with something binding, etc? Flight wise it doesn't seem to effect anything, but I just wanted to see if the disc should be pointing in the exact direction. I am planning on rebuilding the head tomorrow, so this would be a good time to take care of any other problems.

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01-26-2007 10:14 PM  10 years agoPost 2
DarkHorse1

rrApprentice

Gloucester UK

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Cyclic offsets from gyroscopic progression are normal when observed on the ground.

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01-27-2007 04:56 AM  10 years agoPost 3
lowtone20hz

rrNovice

E. Falmouth, MA

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Thought I'd read something about that. Thanks for the info. Now, will it be different when in flight?

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01-27-2007 01:08 PM  10 years agoPost 4
Avropilot

rrVeteran

Murfreesboro, Tennessee

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DH is right. It's called Gyroscopic Procession. A spinnig object that has an outside force applied to it will react 90 degrees later in the direction it rotates. This is how we can ride a bicycle with no hands.

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01-27-2007 02:02 PM  10 years agoPost 5
stickyfox

rrKey Veteran

Rochester, NY - US

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Actually, that's not right. The reason the BCP disc doesn't tilt exactly in the right place is because it's just not 100% perfect. You'll find that in addition to pitching forward, it also rolls slightly to the left. It's a little worse or better depending on how you mix head parts, how much damping you have on the spindle, and whether you've correctly leveled your swash plate.

You gyroscopic precession guys have mistaken reaction with force. Force is invisible; it's the reaction that is observed. If you want the helicopter to roll to the right, you have to lower the right side of the disc. Think about that for a second. If the disc is moving one way, how can the helicopter move any other way? The forces being applied to the disc are advanced by approximately 90°, but you can't see this happening by looking at the helicopter (and it's not the phenomenon that causes the cyclic control to advance.)

To use the bicycle analogy, note that you can still see the handlebars turn when you steer with no hands.

Google for Colin Mill to find out more than you ever wanted to know about this.

-fox

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01-27-2007 05:31 PM  10 years agoPost 6
lowtone20hz

rrNovice

E. Falmouth, MA

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Wow! I just browsed through the Colin Mill site. There's a lot of info there I'll have to get to reading. Thanks for the info. So, the bottom line is that this is not a problem as long as everything is setup right. Thanks guys.

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