REFLECTOR: Aileron self-centering
Al Gietzen
ALVentures at cox.net
Thu Aug 5 11:32:42 CDT 2004
Here’s my take on the torque tube and self-centering. When you put a bend
into the aileron torque tube to align it with the hole in the wing root, it
results in a bending force to the tube as well as a torsional force when
moving the aileron from the bellcrank. The .065 – ¾ aluminum tube in
torsion only is likely quite adequate for a standard wing, and probably the
long wing as well. The bend adds “springy-ness” between the bellcrank and
the aileron. I verified that when I put in the bend, and was a bit
concerned, but I don’t know that is necessarily a problem, at least for the
standard wing.
Using a U-joint doesn’t completely eliminate the bending force, but at such
a small angle reduces in considerably. The reason for bending the tube
instead of using the U-joint was, of course, to eliminate two connections
plus any unlikely play that might be in the U-joint. I went to the bent
tube instead of the U-joint on Alan Shaw’s recommendation.
In my opinion, these effects are likely not related to the “stiction” of
which Lyn speaks. The springy-ness may reduce the “crispness” in the
controls, or limit travel of the ailerons, especially at high speed, but not
cause the lack of precision around neutral position, where the forces on the
torque tubes are small anyway. “Stiction” sounds to me like a combination of
friction and play in the system.
FWIW,
Al
Subject: Re: REFLECTOR: Aileron self-centering
| Fred,
| Maybe the term "self-centering" doesn't give the right picture. Here's
what
| I'm talking about:
|
| OK, you are flying along with no turbulance at 10,000 feet. You want to
make
| a tiny aileron adjustment because the GPS says you are ever so slowly
going
| off-course. So you try to make a tiny adjustment but normal "stiction"
| (sticky friction) in the system makes your adjustment just a tiny bit too
| much so you hunt back and forth a few time and finally you seem to have
it -
| But no you don't, not quite, so you keep at it. After a while you don't
care
| so much about maintaining the course, so you wait until the GPS says your
a
| mile off course and then you adjust it. But then you decide, this is
pretty
| crappy flying - I ought to be able to put the wings dead level and
maintain
| a straight-line course for at least three minutes. So it goes, five hours
of
| constant tiny readjustments of the ailerons to get from the gulf coast to
| home
|
| Maybe the word is "null", there's no null point. If you offset the
ailerons
| 1/1000 inch - That, by god, is where they will stay!
| Maybe I just flew the A36 Bonanza for too many hours before I started
flying
| the Velocity - I'm spoiled.
| Regards,
| Lynn
|
| ----- Original Message -----
| From: "Fred Marconi" <fmarconi at bellsouth.net>
| To: <Jim_Agnew_2 at yahoo.com>; "Velocity Aircraft Owners and Builders list"
| <reflector at tvbf.org>
| Sent: Tuesday, August 03, 2004 9:30 PM
| Subject: Re: REFLECTOR: Aileron self-centering
|
|
| > What am I missing. We have done aileron rolls with N244FM the plane
| > respons beautifully and I have just a standard set up except my tubes
are
| > steel rather than the aluminum.
| >
| > Fred
| >
| > ----- Original Message -----
| > From: "Jim Agnew" <jim_agnew_2 at yahoo.com>
| > To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
| > Sent: Tuesday, August 03, 2004 9:59 PM
| > Subject: Re: REFLECTOR: Aileron self-centering
| >
| >
| > > Ronnie,
| > >
| > > The answer is simple, the AL tube in a direct twisting
| > > application will deliver all of the torque and motion to
| > > the aileron. When it is swung through an arc the AL tub
| > > will suddenly bow when the aileron load becomes to high and
| > > the torque is transformed into a bowing of the tube rather
| > > than moving the aileron.
| > >
| > > Jim
| > > --- Ronnie Brown <romott at adelphia.net> wrote:
| > >
| > > > I'm not sure you have a problem.
| > > >
| > > > The 172 that I flew for 10 years didn't do a very good
| > > > job of returning to
| > > > wings level if you turned the yoke loose while in a turn.
| > > > In fact, if you
| > > > were more than about 20-30 degrees banked, it would turn
| > > > even steeper.
| > > > Called spiral stability - I'm not sure I understand why
| > > > that is desirable in
| > > > a certified airplane.
| > > >
| > > > The tendency for an airplane to return to wings level is
| > > > dihedral effect.
| > > > The Velocity is supposed to be fairly good at trying to
| > > > do this, although I
| > > > haven't really tested this on my 173 Elite RG. You
| > > > wouldn't think the Velo
| > > > would be as good as a C172, since the 172 is hanging
| > > > under its wings - the
| > > > Velo has mid wings, and they go straight out. I guess
| > > > the swept wings
| > > > causes the dihedral effect. I love the way mine flies,
| > > > very stable for
| > > > cross country and IFR. And it handles well at low speed,
| > > > on final. Just
| > > > lands fast like a canard. Otherwise, GREAT airplane!
| > > >
| > > > Having the ailerons set at 1/2" down while centered
| > > > sounds scary. That
| > > > would cause a pretty good pitch "down" effect. Are you
| > > > saying that your
| > > > ailerons go to faired straight neutral while in the air?
| > > > Sounds like
| > > > something is giving too much slop in your aileron control
| > > > linkages?
| > > >
| > > > My ailerons have one piece torque tubes - no connector
| > > > near the aileron end.
| > > > I don't see the slop or give that some folks say they see
| > > > with the "off
| > > > center" aluminum torque tube arrangement. I can't see
| > > > that it matters where
| > > > the torque tube is mounted in relationship to the hinge
| > > > line. As long as
| > > > the torque tube is attached in such a way that it points
| > > > to the aileron bell
| > > > crank at the root of the wing, I don't understand the
| > > > "wrap-up" that you
| > > > mention.
| > > >
| > > > Ronnie
| > > >
| > > >
| > > >
| > > >
| > > >
| > > >
| > > > ----- Original Message -----
| > > > From: "Lynn Gallup" <LGallup at mn.rr.com>
| > > > To: "Velocity Aircraft Owners and Builders list"
| > > > <reflector at tvbf.org>
| > > > Sent: Monday, August 02, 2004 6:17 PM
| > > > Subject: REFLECTOR: Aileron self-centering
| > > >
| > > >
| > > > | Velo-people,
| > > > | A while back I started a thread called "aileron
| > > > stiffness". This really
| > > > | related more to the degree of aileron self-centering
| > > > following a turn than
| > > > | to stiffness per se. On my airplane I thought the
| > > > ailerons displayed
| > > > almost
| > > > | no self-centering in flight and I attributed this to
| > > > stiffness or friction
| > > > | in the system.
| > > > |
| > > > | I noticed that on the ground the aileron control seemed
| > > > fairly smooth and
| > > > | easy compared to in-flight so I decided to reject the
| > > > "stiffness and
| > > > | friction" hypothesis and look elsewhere. I postulated
| > > > that there might be
| > > > | some kind of "slack" or "wrap-up" in the system due,
| > > > possibly, to bending
| > > > of
| > > > | the aileron torque tubes because they are not attached
| > > > at the center of
| > > > | pivot of the ailerons. As an experiment, I adjusted the
| > > > ailerons so they
| > > > had
| > > > | a half-inch of droop when centered. I felt this would
| > > > torque-load the
| > > > system
| > > > | in flight and I should feel at least something
| > > > different. I have now flown
| > > > | the airplane about ten hours this way and pretty much
| > > > put it through it's
| > > > | paces. My feeling is that the change definitely helped
| > > > but not enough.
| > > > |
| > > > | I believe the aileron droop idea is really a
| > > > second-order fix, good enough
| > > > | for an experiment but not the primary factor so I
| > > > really don't want to
| > > > | increase the droop; I might break something - Like my
| > > > head. So I am now
| > > > | thinking about two things (1) replacing the aluminum
| > > > aileron torque tubes
| > > > | with steel and/or (2) installing universal joints where
| > > > the tubes attach
| > > > to
| > > > | the ailerons.
| > > > |
| > > > | Have any of you had any experience with either of these
| > > > ideas?
| > > > |
| > > > | Regards,
| > > > | Lynn
| > > > |
| > > > | _______________________________________________
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| > >
| > >
| > > =====
| > > James F. Agnew
| > > Jim_Agnew_2 at Yahoo.Com
| > > Tampa, FL
| > > Velocity 173 Elite Aircraft Completed & Flying
| > > _______________________________________________
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| > >
| >
| >
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|
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