Yep - had to figure Howard's clown suit was coming out.

OK. I AM WRONG. BRETT IS RIGHT.

Hey! I'm not starting the hero worship yet, just trying to be a good loser - for the record. He did put up with some abuse, but stuff was flying both ways.

>
>The cardboard bellcrank demo has one value. The separation
>between the leadouts and the bellcrank positions, as seen
>along 'flight radii,' acts, but internally, WITHIN the
>structure of the model. The static demo arrangement works
>pretty well for the dynamics in flight, BUT with the
>addition of aerodynamic and thrust effects.
>
>Sharply bent (even flexible) leadouts 'tend' to 'saw' on the
>tip guides, when the bellcrank pivot is not near the CG. (I
>have had a model or two --not recently-- showing this nature
>of wear.) I try to design my models, or redesign existing
>plan and kit originals, subtly, to locate the bellcrank
>pivot very near the CG, and to put the tip leadout guides
>where they meet the 'trail angle' of the lines as they
>approach the wingtip.
>
Agree 100%, and I have the sawed through leadout guides to prove it. A little "face-saving" here, admittedly, but I did offer this opinion in the middle of all the bellcrank stuff (#39. in "Bellcrank #2" thread):

It still sounds like we are agreeing, and the rest may be semantics. Moving the bellcrank may cause undo friction and stress at the leadout guides, and the plane will attempt to rotate to relieve that stress. If that rotation is different than the thrust line (assuming some aerodynamic differences), then yaw will occur in flight. Line rake does the same thing, as everyone will agree. The key is that both are altering the centerline of the mechanism with respect to the orientation of the plane."

maybe it wipes a little egg off ... still suffering in Engineer Eat Crow Heck ...

OK. I AM WRONG. BRETT IS RIGHT.

Well Jim and Tom I did some of my own experiments and found that I have been wrong about the bell crank location for some time. After making a few phone calls and talking to some prominent flyers. The told me to set my own experiments and come to my own conclusion. I did Bill N. is right I'm wrong.

If you use the board and bell crank as described in Bills experiments it makes no difference where it's located.

There you have it.

But Brett I stand on the car thing till I get a answer. I have seen this type thing with my own eyes.

[photo not recovered: 41ab3dc8505eb125.jpg]

No sir... they "ahsillate". How bout ying and yang and "the force be with you"? If it's with me does it mean it's against you? (third law stuff)

hhhhhhhhhhhhhhh.............

I know ... it will be that rotating globe again, it is another 1/4 of globe to east then we are ...

... hmmm... it could be also that unballanced force pushing your tail down ... isnt't it?

Aside from the giggles we're headed for, I'll stand with Igor on the simple "always in balance" declaration.

When an unopposed force acts on a 'free body' it causes the body to move in a manner related to the unopposed force, right? The body has mass. The force accelerates that mass, and during that acceleration the rate of acceleration and the force ARE in instantaneous balance.

Balance doesn't always mean 'static' (unmoving) conditions. For our models I think static experiments are of little -- if any -- value more often than not.

I expect you knew this stuff long since. But to clarify for those who may not have, that odd wording about how the force moves the free body is there for a reason. If you push in any direction except straight at the body's center of mass, the result will include rotation AND translation (movement in the force's direction.) It's unlikely to cause rotation ONLY, or translation ONLY.

Aside and under my breath... good that he explained it.

I thought I said that. As a matter of fact, Post #65 in the original jim ivey, "bellcrank position" thread:

"No offense to all of the effort of repeating the former articles, studies, etc., but they all talk about dead weights on a string. How is that a valid comparison to the complicated (yes - I said complicated) forces at play with a flying airplane?. Yes, all things will equalize toward some center of gravity, but at what yaw angle, and is it the CG we measure at rest?"

Things degenerated from there into a discussion about whether the dynamic flight forces were complicated(?!) ... then I got trapped into arguing the force diagrams after Howard's clown suit proof.

This is beating a dead horse in the argument - except for some more giggles. It has been fun.