Just Another Thought on Wheel Camber


withidl <dwithington@...>
 

In an effort to understand the physics surrounding the ground
handling problems of the plans built Q-Bird (I'm still building
#2710) I have tried many times to visualize the problem. Several
months ago while I was reviewing an article in a motorcycle magazine
(I have a 1999 Suzuki GSX1300R Hayabusa) regarding how a motorcycle
executes a turn it became clear to me that the negative camber of
the plans built Q-Bird creates ground control problems basis the
same physics as that of a motorcycle leaned over into a turn.

When a motorcycle at speed is counter steered into a turn the wheels
lean (can't call it +/- camber because there's no left or
right
wheel reference), YET ONCE IN THE TURN THE MOTORCYCLE'S FRONT
WHEEL
IS STILL POINTED STRAIGHT AHEAD EVEN THOUGH THE CYCLE IS TURNING,
i.e. its angle to the chassis is such that it is not actually
turning the motorcycle as the front wheels of a car do (NOTE: At
very slow speed the front wheel DOES steer the cycle as per a car).
The motorcycle turns because it's lean sets up a virtual
"cone" from
the axles of BOTH wheels to a projected point on the ground vs. the
tires contact patch to that same projected point on the ground. As
you know, if you roll a conical object on a flat surface it will
turn around its pointed end. This works great for a motorcycle
since the two wheels are acting in concert with one another.

On the other hand the negative camber of the Q-Bird's landing
gear
oppose one another, i.e. they lean AGAINST each other, each trying
to turn the plane toward the opposite side of the runway. As long
as each wheel is carrying the same load all is balanced. As
downward pressure on a wheel increases, either due to yaw inputs by
the pilot, runway bumps or crosswinds, two things happen. The
canard flex increases which increases negative camber (the
motorcycle is leaned further, thus more turning effort is generated)
and the wheels tractive authority increases, both of which
exacerbate yaw control problems because the pilot has no timely way
to anticipate or correct for them. The plans change 2 degree toe
out was an effort to counteract this but just can't totally do so
because of the constantly changing camber (canard flex) and wheel
tractive authority.

So all the above being said, correcting the camber at maximum canard
flex toward a neutral or positive position when the aircraft is at
gross is a good thing. Excessive positive camber would have little
adverse affect on the Q-Bird since it would only evidence when the
plane is being turned toward the inside wheel (with the increasing
positive camber) which would be lifting and thus lessening it's
tractive authority and thereby negating any potential deleterious
effect the positive camber may have.

There have been more technical explanations on the
"negatives" of
negative camber on the Q-Bird, but I thought the above may offer a
more elementary perspective for those of us not into the physics of
the matter.

Additionally, not all negative camber is bad, as my highway vehicle
has considerable OEM negative camber on the rear wheels to enhance
stability, just depends on the application.


David J. Gall
 

Nicely said. You could extend this to explain "reverse aileron steering,"
too.


David J. Gall

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...]
On Behalf Of withidl
Sent: Wednesday, June 22, 2005 9:02 PM
To: Q-LIST@...
Subject: [Q-LIST] Just Another Thought on Wheel Camber

In an effort to understand the physics surrounding the ground
handling problems of the plans built Q-Bird (I'm still building
#2710) I have tried many times to visualize the problem.
Several months ago while I was reviewing an article in a
motorcycle magazine (I have a 1999 Suzuki GSX1300R Hayabusa)
regarding how a motorcycle executes a turn it became clear to
me that the negative camber of the plans built Q-Bird creates
ground control problems basis the same physics as that of a
motorcycle leaned over into a turn.

When a motorcycle at speed is counter steered into a turn the
wheels lean (can't call it +/- camber because there's no left
or right wheel reference), YET ONCE IN THE TURN THE
MOTORCYCLE'S FRONT WHEEL IS STILL POINTED STRAIGHT AHEAD EVEN
THOUGH THE CYCLE IS TURNING, i.e. its angle to the chassis is
such that it is not actually turning the motorcycle as the
front wheels of a car do (NOTE: At very slow speed the front
wheel DOES steer the cycle as per a car).
The motorcycle turns because it's lean sets up a virtual
"cone" from the axles of BOTH wheels to a projected point on
the ground vs. the tires contact patch to that same projected
point on the ground. As you know, if you roll a conical
object on a flat surface it will turn around its pointed end.
This works great for a motorcycle since the two wheels are
acting in concert with one another.

On the other hand the negative camber of the Q-Bird's landing
gear oppose one another, i.e. they lean AGAINST each other,
each trying
to turn the plane toward the opposite side of the runway. As long
as each wheel is carrying the same load all is balanced. As
downward pressure on a wheel increases, either due to yaw
inputs by the pilot, runway bumps or crosswinds, two things
happen. The canard flex increases which increases negative
camber (the motorcycle is leaned further, thus more turning
effort is generated) and the wheels tractive authority
increases, both of which exacerbate yaw control problems
because the pilot has no timely way to anticipate or correct
for them. The plans change 2 degree toe out was an effort to
counteract this but just can't totally do so because of the
constantly changing camber (canard flex) and wheel tractive authority.

So all the above being said, correcting the camber at maximum
canard flex toward a neutral or positive position when the
aircraft is at gross is a good thing. Excessive positive
camber would have little adverse affect on the Q-Bird since
it would only evidence when the plane is being turned toward
the inside wheel (with the increasing positive camber) which
would be lifting and thus lessening it's tractive authority
and thereby negating any potential deleterious effect the
positive camber may have.

There have been more technical explanations on the
"negatives" of negative camber on the Q-Bird, but I thought
the above may offer a more elementary perspective for those
of us not into the physics of the matter.

Additionally, not all negative camber is bad, as my highway
vehicle has considerable OEM negative camber on the rear
wheels to enhance stability, just depends on the application.


withidl <dwithington@...>
 

David, I appreciate your lending credibility to my analysis!

I hadn't thought about the "reverse aileron steering", but now
you've caused me to do so and I understand what you say as follows.

When a Q-Bird with negative wheel camber is at speed on the runway
and right aileron is input the Q-Bird attempts to roll right thereby
putting additional load on the right wheel and less on the left
wheel. This further flexes the right canard causing additional
negative camber on the right wheel (motorcycle is leaned further to
the left) along with additional tractive authority so that the right
wheel turns the Q-Bird to the left.

So by negating negative camber those two Q-Bird problems are killed
with that one stone.

--- In Q-LIST@..., "David J. Gall" <David@G...> wrote:
Nicely said. You could extend this to explain "reverse aileron
steering,"
too.


David J. Gall

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...]
On Behalf Of withidl
Sent: Wednesday, June 22, 2005 9:02 PM
To: Q-LIST@...
Subject: [Q-LIST] Just Another Thought on Wheel Camber

In an effort to understand the physics surrounding the ground
handling problems of the plans built Q-Bird (I'm still building
#2710) I have tried many times to visualize the problem.
Several months ago while I was reviewing an article in a
motorcycle magazine (I have a 1999 Suzuki GSX1300R Hayabusa)
regarding how a motorcycle executes a turn it became clear to
me that the negative camber of the plans built Q-Bird creates
ground control problems basis the same physics as that of a
motorcycle leaned over into a turn.

When a motorcycle at speed is counter steered into a turn the
wheels lean (can't call it +/- camber because there's no left
or right wheel reference), YET ONCE IN THE TURN THE
MOTORCYCLE'S FRONT WHEEL IS STILL POINTED STRAIGHT AHEAD EVEN
THOUGH THE CYCLE IS TURNING, i.e. its angle to the chassis is
such that it is not actually turning the motorcycle as the
front wheels of a car do (NOTE: At very slow speed the front
wheel DOES steer the cycle as per a car).
The motorcycle turns because it's lean sets up a virtual
"cone" from the axles of BOTH wheels to a projected point on
the ground vs. the tires contact patch to that same projected
point on the ground. As you know, if you roll a conical
object on a flat surface it will turn around its pointed end.
This works great for a motorcycle since the two wheels are
acting in concert with one another.

On the other hand the negative camber of the Q-Bird's landing
gear oppose one another, i.e. they lean AGAINST each other,
each trying
to turn the plane toward the opposite side of the runway. As
long
as each wheel is carrying the same load all is balanced. As
downward pressure on a wheel increases, either due to yaw
inputs by the pilot, runway bumps or crosswinds, two things
happen. The canard flex increases which increases negative
camber (the motorcycle is leaned further, thus more turning
effort is generated) and the wheels tractive authority
increases, both of which exacerbate yaw control problems
because the pilot has no timely way to anticipate or correct
for them. The plans change 2 degree toe out was an effort to
counteract this but just can't totally do so because of the
constantly changing camber (canard flex) and wheel tractive
authority.

So all the above being said, correcting the camber at maximum
canard flex toward a neutral or positive position when the
aircraft is at gross is a good thing. Excessive positive
camber would have little adverse affect on the Q-Bird since
it would only evidence when the plane is being turned toward
the inside wheel (with the increasing positive camber) which
would be lifting and thus lessening it's tractive authority
and thereby negating any potential deleterious effect the
positive camber may have.

There have been more technical explanations on the
"negatives" of negative camber on the Q-Bird, but I thought
the above may offer a more elementary perspective for those
of us not into the physics of the matter.

Additionally, not all negative camber is bad, as my highway
vehicle has considerable OEM negative camber on the rear
wheels to enhance stability, just depends on the application.


Bob Farnam <bfarnam@...>
 

Don't over complicate this, guys. Reverse aileron steering is nothing more
than adverse yaw amplified by the angle of attack of a taildragger.

Bob F.
N200QK
EAA Flight Advisor

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...]On Behalf Of
withidl
Sent: Thursday, June 23, 2005 3:12 PM
To: Q-LIST@...
Subject: [Q-LIST] Re: Just Another Thought on Wheel Camber


David, I appreciate your lending credibility to my analysis!

I hadn't thought about the "reverse aileron steering", but now
you've caused me to do so and I understand what you say as follows.

When a Q-Bird with negative wheel camber is at speed on the runway
and right aileron is input the Q-Bird attempts to roll right thereby
putting additional load on the right wheel and less on the left
wheel. This further flexes the right canard causing additional
negative camber on the right wheel (motorcycle is leaned further to
the left) along with additional tractive authority so that the right
wheel turns the Q-Bird to the left.

So by negating negative camber those two Q-Bird problems are killed
with that one stone.

--- In Q-LIST@..., "David J. Gall" <David@G...> wrote:
> Nicely said. You could extend this to explain "reverse aileron
steering,"
> too.
>
>
> David J. Gall
>
> > -----Original Message-----
> > From: Q-LIST@... [mailto:Q-LIST@...]
> > On Behalf Of withidl
> > Sent: Wednesday, June 22, 2005 9:02 PM
> > To: Q-LIST@...
> > Subject: [Q-LIST] Just Another Thought on Wheel Camber
> >
> > In an effort to understand the physics surrounding the ground
> > handling problems of the plans built Q-Bird (I'm still building
> > #2710) I have tried many times to visualize the problem.
> > Several months ago while I was reviewing an article in a
> > motorcycle magazine (I have a 1999 Suzuki GSX1300R Hayabusa)
> > regarding how a motorcycle executes a turn it became clear to
> > me that the negative camber of the plans built Q-Bird creates
> > ground control problems basis the same physics as that of a
> > motorcycle leaned over into a turn.
> >
> > When a motorcycle at speed is counter steered into a turn the
> > wheels lean (can't call it +/- camber because there's no left
> > or right wheel reference), YET ONCE IN THE TURN THE
> > MOTORCYCLE'S FRONT WHEEL IS STILL POINTED STRAIGHT AHEAD EVEN
> > THOUGH THE CYCLE IS TURNING, i.e. its angle to the chassis is
> > such that it is not actually turning the motorcycle as the
> > front wheels of a car do (NOTE: At very slow speed the front
> > wheel DOES steer the cycle as per a car).
> > The motorcycle turns because it's lean sets up a virtual
> > "cone" from the axles of BOTH wheels to a projected point on
> > the ground vs. the tires contact patch to that same projected
> > point on the ground. As you know, if you roll a conical
> > object on a flat surface it will turn around its pointed end.
> > This works great for a motorcycle since the two wheels are
> > acting in concert with one another.
> >
> > On the other hand the negative camber of the Q-Bird's landing
> > gear oppose one another, i.e. they lean AGAINST each other,
> > each trying
> > to turn the plane toward the opposite side of the runway. As
long
> > as each wheel is carrying the same load all is balanced. As
> > downward pressure on a wheel increases, either due to yaw
> > inputs by the pilot, runway bumps or crosswinds, two things
> > happen. The canard flex increases which increases negative
> > camber (the motorcycle is leaned further, thus more turning
> > effort is generated) and the wheels tractive authority
> > increases, both of which exacerbate yaw control problems
> > because the pilot has no timely way to anticipate or correct
> > for them. The plans change 2 degree toe out was an effort to
> > counteract this but just can't totally do so because of the
> > constantly changing camber (canard flex) and wheel tractive
authority.
> >
> > So all the above being said, correcting the camber at maximum
> > canard flex toward a neutral or positive position when the
> > aircraft is at gross is a good thing. Excessive positive
> > camber would have little adverse affect on the Q-Bird since
> > it would only evidence when the plane is being turned toward
> > the inside wheel (with the increasing positive camber) which
> > would be lifting and thus lessening it's tractive authority
> > and thereby negating any potential deleterious effect the
> > positive camber may have.
> >
> > There have been more technical explanations on the
> > "negatives" of negative camber on the Q-Bird, but I thought
> > the above may offer a more elementary perspective for those
> > of us not into the physics of the matter.
> >
> > Additionally, not all negative camber is bad, as my highway
> > vehicle has considerable OEM negative camber on the rear
> > wheels to enhance stability, just depends on the application.




Quickie Builders Association WEB site
http://www.quickiebuilders.org





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Mark Robinson
 

Reverse aileron steering also works (well) on my Tri-Q2. Seems to be
the result of adverse yaw in the direction of the "high lift" wing. I
find myself taking advantage of it more and more.


--- In Q-LIST@..., "Bob Farnam" <bfarnam@p...> wrote:
Don't over complicate this, guys. Reverse aileron steering is
nothing more
than adverse yaw amplified by the angle of attack of a taildragger.

Bob F.
N200QK
EAA Flight Advisor

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...]On
Behalf Of
withidl
Sent: Thursday, June 23, 2005 3:12 PM
To: Q-LIST@...
Subject: [Q-LIST] Re: Just Another Thought on Wheel Camber


David, I appreciate your lending credibility to my analysis!

I hadn't thought about the "reverse aileron steering", but now
you've caused me to do so and I understand what you say as
follows.

When a Q-Bird with negative wheel camber is at speed on the runway
and right aileron is input the Q-Bird attempts to roll right
thereby
putting additional load on the right wheel and less on the left
wheel. This further flexes the right canard causing additional
negative camber on the right wheel (motorcycle is leaned further
to
the left) along with additional tractive authority so that the
right
wheel turns the Q-Bird to the left.

So by negating negative camber those two Q-Bird problems are
killed
with that one stone.

--- In Q-LIST@..., "David J. Gall" <David@G...> wrote:
> Nicely said. You could extend this to explain "reverse aileron
steering,"
> too.
>
>
> David J. Gall
>
> > -----Original Message-----
> > From: Q-LIST@... [mailto:Q-LIST@...]
> > On Behalf Of withidl
> > Sent: Wednesday, June 22, 2005 9:02 PM
> > To: Q-LIST@...
> > Subject: [Q-LIST] Just Another Thought on Wheel Camber
> >
> > In an effort to understand the physics surrounding the ground
> > handling problems of the plans built Q-Bird (I'm still
building
> > #2710) I have tried many times to visualize the problem.
> > Several months ago while I was reviewing an article in a
> > motorcycle magazine (I have a 1999 Suzuki GSX1300R Hayabusa)
> > regarding how a motorcycle executes a turn it became clear to
> > me that the negative camber of the plans built Q-Bird creates
> > ground control problems basis the same physics as that of a
> > motorcycle leaned over into a turn.
> >
> > When a motorcycle at speed is counter steered into a turn the
> > wheels lean (can't call it +/- camber because there's no left
> > or right wheel reference), YET ONCE IN THE TURN THE
> > MOTORCYCLE'S FRONT WHEEL IS STILL POINTED STRAIGHT AHEAD EVEN
> > THOUGH THE CYCLE IS TURNING, i.e. its angle to the chassis is
> > such that it is not actually turning the motorcycle as the
> > front wheels of a car do (NOTE: At very slow speed the front
> > wheel DOES steer the cycle as per a car).
> > The motorcycle turns because it's lean sets up a virtual
> > "cone" from the axles of BOTH wheels to a projected point on
> > the ground vs. the tires contact patch to that same projected
> > point on the ground. As you know, if you roll a conical
> > object on a flat surface it will turn around its pointed end.
> > This works great for a motorcycle since the two wheels are
> > acting in concert with one another.
> >
> > On the other hand the negative camber of the Q-Bird's landing
> > gear oppose one another, i.e. they lean AGAINST each other,
> > each trying
> > to turn the plane toward the opposite side of the runway. As
long
> > as each wheel is carrying the same load all is balanced. As
> > downward pressure on a wheel increases, either due to yaw
> > inputs by the pilot, runway bumps or crosswinds, two things
> > happen. The canard flex increases which increases negative
> > camber (the motorcycle is leaned further, thus more turning
> > effort is generated) and the wheels tractive authority
> > increases, both of which exacerbate yaw control problems
> > because the pilot has no timely way to anticipate or correct
> > for them. The plans change 2 degree toe out was an effort to
> > counteract this but just can't totally do so because of the
> > constantly changing camber (canard flex) and wheel tractive
authority.
> >
> > So all the above being said, correcting the camber at maximum
> > canard flex toward a neutral or positive position when the
> > aircraft is at gross is a good thing. Excessive positive
> > camber would have little adverse affect on the Q-Bird since
> > it would only evidence when the plane is being turned toward
> > the inside wheel (with the increasing positive camber) which
> > would be lifting and thus lessening it's tractive authority
> > and thereby negating any potential deleterious effect the
> > positive camber may have.
> >
> > There have been more technical explanations on the
> > "negatives" of negative camber on the Q-Bird, but I thought
> > the above may offer a more elementary perspective for those
> > of us not into the physics of the matter.
> >
> > Additionally, not all negative camber is bad, as my highway
> > vehicle has considerable OEM negative camber on the rear
> > wheels to enhance stability, just depends on the application.




Quickie Builders Association WEB site
http://www.quickiebuilders.org





--------------------------------------------------------------------
--------
--
Yahoo! Groups Links

a.. To visit your group on the web, go to:
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David J. Gall
 

I don't think reverse aileron steering is eliminated by setting positive camber. You still have the same flexible canard causing a difference in camber between the left and right wheels when a moment is applied about the roll axis. Adverse yaw may also play a part. The important thing is the directional instability caused by having negative camber, and the benefit available by setting the camber positive.


David J. Gall

----- Original Message -----
From: withidl <dwithington@...>
To: Q-LIST@...
Subject: [Q-LIST] Re: Just Another Thought on Wheel Camber
Date: Thu, 23 Jun 2005 22:11:39 -0000


David, I appreciate your lending credibility to my analysis!

I hadn't thought about the "reverse aileron steering", but now
you've caused me to do so and I understand what you say as follows.

When a Q-Bird with negative wheel camber is at speed on the runway
and right aileron is input the Q-Bird attempts to roll right thereby
putting additional load on the right wheel and less on the left
wheel. This further flexes the right canard causing additional
negative camber on the right wheel (motorcycle is leaned further to
the left) along with additional tractive authority so that the right
wheel turns the Q-Bird to the left.

So by negating negative camber those two Q-Bird problems are killed
with that one stone.

--- In Q-LIST@..., "David J. Gall" <David@G...> wrote:
Nicely said. You could extend this to explain "reverse aileron
steering,"
too.


David J. Gall

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] > On Behalf
Of withidl
Sent: Wednesday, June 22, 2005 9:02 PM
To: Q-LIST@...
Subject: [Q-LIST] Just Another Thought on Wheel Camber
In an effort to understand the physics surrounding the ground > handling
problems of the plans built Q-Bird (I'm still building
#2710) I have tried many times to visualize the problem. > Several months
ago while I was reviewing an article in a > motorcycle magazine (I have a
1999 Suzuki GSX1300R Hayabusa) > regarding how a motorcycle executes a turn
it became clear to > me that the negative camber of the plans built Q-Bird
creates > ground control problems basis the same physics as that of a >
motorcycle leaned over into a turn.
When a motorcycle at speed is counter steered into a turn the > wheels
lean (can't call it +/- camber because there's no left > or right wheel
reference), YET ONCE IN THE TURN THE > MOTORCYCLE'S FRONT WHEEL IS STILL
POINTED STRAIGHT AHEAD EVEN > THOUGH THE CYCLE IS TURNING, i.e. its angle to
the chassis is > such that it is not actually turning the motorcycle as the
front wheels of a car do (NOTE: At very slow speed the front > wheel DOES
steer the cycle as per a car). > The motorcycle turns because it's lean
sets up a virtual > "cone" from the axles of BOTH wheels to a projected
point on > the ground vs. the tires contact patch to that same projected >
point on the ground. As you know, if you roll a conical > object on a flat
surface it will turn around its pointed end. > This works great for a
motorcycle since the two wheels are > acting in concert with one another. >
On the other hand the negative camber of the Q-Bird's landing > gear
oppose one another, i.e. they lean AGAINST each other, > each trying > to
turn the plane toward the opposite side of the runway. As
long
as each wheel is carrying the same load all is balanced. As > downward
pressure on a wheel increases, either due to yaw > inputs by the pilot,
runway bumps or crosswinds, two things > happen. The canard flex increases
which increases negative > camber (the motorcycle is leaned further, thus
more turning > effort is generated) and the wheels tractive authority >
increases, both of which exacerbate yaw control problems > because the pilot
has no timely way to anticipate or correct > for them. The plans change 2
degree toe out was an effort to > counteract this but just can't totally do
so because of the > constantly changing camber (canard flex) and wheel
tractive
authority.
So all the above being said, correcting the camber at maximum > canard
flex toward a neutral or positive position when the > aircraft is at gross
is a good thing. Excessive positive > camber would have little adverse
affect on the Q-Bird since > it would only evidence when the plane is being
turned toward > the inside wheel (with the increasing positive camber) which
would be lifting and thus lessening it's tractive authority > and thereby
negating any potential deleterious effect the > positive camber may have. >
There have been more technical explanations on the > "negatives" of
negative camber on the Q-Bird, but I thought > the above may offer a more
elementary perspective for those > of us not into the physics of the matter.
Additionally, not all negative camber is bad, as my highway > vehicle
has considerable OEM negative camber on the rear > wheels to enhance
stability, just depends on the application.



Quickie Builders Association WEB site
http://www.quickiebuilders.org


Yahoo! Groups Links




David J. Gall
 

Bob,

Respectfully, I disagree. It may also be adverse yaw, but it is also something more than just adverse yaw.


David J. Gall

----- Original Message -----
From: "Bob Farnam" <bfarnam@...>
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: Just Another Thought on Wheel Camber
Date: Thu, 23 Jun 2005 16:41:35 -0700


Don't over complicate this, guys. Reverse aileron steering is nothing more
than adverse yaw amplified by the angle of attack of a taildragger.

Bob F.
N200QK
EAA Flight Advisor


Larry Severson
 

I have followed the discussion on camber with interest. However, I feel
that it is incomplete. On the conventional Q2 tail dragger with tip gear,
the camber goers more negative as the weight in the cockpit goes up. This
does cause squirrelly control. However, it has little or no impact on take
off because the engine is pulling the aircraft forward reducing the
tendency for the TW is swap ends. On landing, the lift furnished by the
canard reduces the bowing on the canard that causes the negative camber
situation until speed reduces. This explains why all of my ground loops
have been at 25 or less MPH.

Putting in positive camber will reduce the possibility of negative camber
at low speed; however, any camber is going to have an impact on
controllability. Putting in positive camber means that non-neutral camber
is present at high speed, with neutral camber at low speeds. What I would
NOT like would be to have the controllability problem transferred to a
higher speed regime. At 25MPH or less, a ground loop is non-destructive. I
would worry at higher speeds.

Now that I think I have a handle on my problem, I will take appropriate
action, while leaving the camber alone.

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...


Bruce Crain
 

Get a Tri Gear and forget about it. ;o)
Bruce Crain
N96BJ

-- larry severson <larry2@...> wrote:
I have followed the discussion on camber with interest. However, I feel
that it is incomplete. On the conventional Q2 tail dragger with tip gear,
the camber goers more negative as the weight in the cockpit goes up. This
does cause squirrelly control. However, it has little or no impact on take
off because the engine is pulling the aircraft forward reducing the
tendency for the TW is swap ends. On landing, the lift furnished by the
canard reduces the bowing on the canard that causes the negative camber
situation until speed reduces. This explains why all of my ground loops
have been at 25 or less MPH.

Putting in positive camber will reduce the possibility of negative camber
at low speed; however, any camber is going to have an impact on
controllability. Putting in positive camber means that non-neutral camber
is present at high speed, with neutral camber at low speeds. What I would
NOT like would be to have the controllability problem transferred to a
higher speed regime. At 25MPH or less, a ground loop is non-destructive. I
would worry at higher speeds.

Now that I think I have a handle on my problem, I will take appropriate
action, while leaving the camber alone.

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...





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britmcman99
 

Bruce:

That's "Try-Gear";)

Phil
N870BM


Sam Hoskins <shoskins@...>
 

In my experience, the single most effective way (and easiest) to fix
stability problems, at any speed, is the Gall alignment. Have you checked
this critical item?

Sam

www.samhoskins.blogspot.com <http://www.samhoskins.blogspot.com/>





_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
larry severson
Sent: Sunday, June 26, 2005 11:49 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: Just Another Thought on Wheel Camber



I have followed the discussion on camber with interest. However, I feel
that it is incomplete. On the conventional Q2 tail dragger with tip gear,
the camber goers more negative as the weight in the cockpit goes up. This
does cause squirrelly control. However, it has little or no impact on take
off because the engine is pulling the aircraft forward reducing the
tendency for the TW is swap ends. On landing, the lift furnished by the
canard reduces the bowing on the canard that causes the negative camber
situation until speed reduces. This explains why all of my ground loops
have been at 25 or less MPH.

Putting in positive camber will reduce the possibility of negative camber
at low speed; however, any camber is going to have an impact on
controllability. Putting in positive camber means that non-neutral camber
is present at high speed, with neutral camber at low speeds. What I would
NOT like would be to have the controllability problem transferred to a
higher speed regime. At 25MPH or less, a ground loop is non-destructive. I
would worry at higher speeds.

Now that I think I have a handle on my problem, I will take appropriate
action, while leaving the camber alone.

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...





Quickie Builders Association WEB site
http://www.quickiebuilders.org






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David J. Gall
 

Larry,

Thrust is destabilizing. Camber change due to canard "bowing" under
aerodynamic lift at 1 gee is approximately 40% of camber change due to canard
bowing due to airplane weight fully supported by the wheels alone.

Negative camber (on the main gear of a taildragger) is destabilizing. Positive camber is stabilizing. Positive camber
will not "transfer the controllability problem to a higher speed regime."

The problem with negative camber is that it responds to small roll
perturbations by pushing the airplane to turn in a direction opposite to the
roll perturbation. This "feeds back" with an amplification of the initial roll
perturbation (due to the height of the CG above the ground), making the
turning force increase, making even more roll, making the turn harder, etc.
etc. etc. This is static and dynamic instability: divergence.

Without going into further detail, this situation first manifests itself at some "critical
speed" and then gets worse the faster you go. You can rudder dance your way through it to liftoff speed, or, perhaps, you can't. You might be able to rudder dance your way through the deceleration after landing, too. Or, perhaps, not.

Positive camber responds to a small roll perturbation with a turn in the same
direction as the perturbation. This "feeds back" as an attenuation of the
initial roll perturbation, thereby lessening the severity of the turn force.
This is static stability. It's not perfect, but it makes the rudder dance a little less exciting.

If you want perfect directional stability, use a locking tailwheel and a laterally stiff tailspring. Or lock your ankles stiffly and use finger brakes. Or build a tri-gear.

With static stability, you have a much better chance of retaining
controllability. Please note that controllability is a completely separate topic. Yes, stability influences controllability. A more unstable craft will respond more aggressively to smaller control inputs. Or, instability can masquerade as a lack of control authority by responding opposite to control inputs. This is what happens with the Q2/200 tailwheel (in my opinion). Yes, control (as in active control, the stuff of brain matter and advanced guidance computers) can "overcome" instability by brute force and quick reflexes, as in the Jim-Bob six pack without the "Gall alignment." Or you can sacrifice some controllability and use a locking tailwheel for directional stability during takeoff and landing.

Do whatever you want. I have it on good authority that the alignment works. The Jim-Bob six pack also works. They work well together. If you're building a Quickie or a Q2 or a Q200, I would consider it MANDATORY that you incorporate all of the six-pack mods, except perhaps the reflexor might not be needed on the Quickie. I would also argue that the alignment should be adjusted, but some people have found success without doing that. Others have found success doing ONLY that. You decide. You could build a larger rudder if you want to enter that debate.

But whatever you do, please know that:

1) somebody else has been there and done that and found out the hard way so you don't have to (and published the easy way for your benefit).

2) Your analysis is erroneous.

Respectfully,


David J. Gall
(Now, back to working on the airplane....)

----- Original Message -----
From: "larry severson" <larry2@...>
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: Just Another Thought on Wheel Camber
Date: Sun, 26 Jun 2005 09:48:54 -0700


I have followed the discussion on camber with interest. However, I feel
that it is incomplete. On the conventional Q2 tail dragger with tip gear,
the camber goers more negative as the weight in the cockpit goes up. This
does cause squirrelly control. However, it has little or no impact on take
off because the engine is pulling the aircraft forward reducing the
tendency for the TW is swap ends. On landing, the lift furnished by the
canard reduces the bowing on the canard that causes the negative camber
situation until speed reduces. This explains why all of my ground loops
have been at 25 or less MPH.

Putting in positive camber will reduce the possibility of negative camber
at low speed; however, any camber is going to have an impact on
controllability. Putting in positive camber means that non-neutral camber
is present at high speed, with neutral camber at low speeds. What I would
NOT like would be to have the controllability problem transferred to a
higher speed regime. At 25MPH or less, a ground loop is non-destructive. I
would worry at higher speeds.

Now that I think I have a handle on my problem, I will take appropriate
action, while leaving the camber alone.

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...


Bruce Crain
 

Yuk Yuk!
Hey, Try-Gear guys are people to ya' know!
It is nice when you just "fling 'er on to da' runway and the try-gear practically stears it in the right direction".

"Trike Wuss"
(No maybe that's Tripod)
Bruce



-- britmcman@... wrote:
Bruce:

That's "Try-Gear";)

Phil
N870BM






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http://www.quickiebuilders.org


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Larry Severson
 

At 05:22 PM 6/26/2005 +0000, you wrote:

Get a Tri Gear and forget about it. ;o)
Bruce Crain
N96BJ
I have seen requests for information on the conversion. I have never seen a
response.


Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...


Larry Severson
 

At 04:57 PM 6/26/2005 -0500, you wrote:
In my experience, the single most effective way (and easiest) to fix
stability problems, at any speed, is the Gall alignment. Have you checked
this critical item?
I studied it. I admit to being simple. I did not understand the logic.


Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...


Larry Severson
 

Negative camber (on the main gear of a taildragger) is destabilizing.
Positive camber is stabilizing. Positive camber
will not "transfer the controllability problem to a higher speed regime."
I stand corrected. How much positive camber should the wheels have at rest?

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...


Bruce Crain
 

The TriQ conversions are hidden in garages and hanger etc. It is hard to find one so you have to be persistent. You also should try and find the larger nose gear as it is much tougher. Also hard to come by.
Bruce



-- larry severson <larry2@...> wrote:
At 05:22 PM 6/26/2005 +0000, you wrote:

Get a Tri Gear and forget about it. ;o)
Bruce Crain
N96BJ
I have seen requests for information on the conversion. I have never seen a
response.


Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...





Quickie Builders Association WEB site
http://www.quickiebuilders.org


Yahoo! Groups Links






___________________________________________________________________
Get Juno Platinum for as low as $6.95/month!
Unlimited Internet Access with 250MB of Email Storage.
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James Postma <james@...>
 

I agree with David. I have about the same reverse aileron steering after
doing the wheel alinement as before.'

James Postma
Q2 Revmaster N145EX
Q2 Revmaster with LS-1
Q200 N8427
Steilacoom, Washington
(253) 584-1182 9:00 to 8:00 PDT
May your header tank be always full and your wings right side up.

----- Original Message -----
From: "David Gall" <David@...>
To: <Q-LIST@...>
Sent: Friday, June 24, 2005 11:26 AM
Subject: Re: [Q-LIST] Re: Just Another Thought on Wheel Camber


I don't think reverse aileron steering is eliminated by setting positive
camber. You still have the same flexible canard causing a difference in
camber between the left and right wheels when a moment is applied about the
roll axis. Adverse yaw may also play a part. The important thing is the
directional instability caused by having negative camber, and the benefit
available by setting the camber positive.


David J. Gall

----- Original Message -----
From: withidl <dwithington@...>
To: Q-LIST@...
Subject: [Q-LIST] Re: Just Another Thought on Wheel Camber
Date: Thu, 23 Jun 2005 22:11:39 -0000


David, I appreciate your lending credibility to my analysis!

I hadn't thought about the "reverse aileron steering", but now
you've caused me to do so and I understand what you say as follows.

When a Q-Bird with negative wheel camber is at speed on the runway
and right aileron is input the Q-Bird attempts to roll right thereby
putting additional load on the right wheel and less on the left
wheel. This further flexes the right canard causing additional
negative camber on the right wheel (motorcycle is leaned further to
the left) along with additional tractive authority so that the right
wheel turns the Q-Bird to the left.

So by negating negative camber those two Q-Bird problems are killed
with that one stone.

--- In Q-LIST@..., "David J. Gall" <David@G...> wrote:
Nicely said. You could extend this to explain "reverse aileron
steering,"
too.


David J. Gall

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] > On
Behalf
Of withidl
Sent: Wednesday, June 22, 2005 9:02 PM
To: Q-LIST@...
Subject: [Q-LIST] Just Another Thought on Wheel Camber
In an effort to understand the physics surrounding the ground >
handling
problems of the plans built Q-Bird (I'm still building
#2710) I have tried many times to visualize the problem. > Several
months
ago while I was reviewing an article in a > motorcycle magazine (I
have a
1999 Suzuki GSX1300R Hayabusa) > regarding how a motorcycle executes a
turn
it became clear to > me that the negative camber of the plans built
Q-Bird
creates > ground control problems basis the same physics as that of a
motorcycle leaned over into a turn.
When a motorcycle at speed is counter steered into a turn the >
wheels
lean (can't call it +/- camber because there's no left > or right
wheel
reference), YET ONCE IN THE TURN THE > MOTORCYCLE'S FRONT WHEEL IS
STILL
POINTED STRAIGHT AHEAD EVEN > THOUGH THE CYCLE IS TURNING, i.e. its
angle to
the chassis is > such that it is not actually turning the motorcycle
as the
front wheels of a car do (NOTE: At very slow speed the front >
wheel DOES
steer the cycle as per a car). > The motorcycle turns because it's
lean
sets up a virtual > "cone" from the axles of BOTH wheels to a
projected
point on > the ground vs. the tires contact patch to that same
projected >
point on the ground. As you know, if you roll a conical > object on a
flat
surface it will turn around its pointed end. > This works great for a
motorcycle since the two wheels are > acting in concert with one
another. >
On the other hand the negative camber of the Q-Bird's landing > gear
oppose one another, i.e. they lean AGAINST each other, > each trying >
to
turn the plane toward the opposite side of the runway. As
long
as each wheel is carrying the same load all is balanced. As >
downward
pressure on a wheel increases, either due to yaw > inputs by the
pilot,
runway bumps or crosswinds, two things > happen. The canard flex
increases
which increases negative > camber (the motorcycle is leaned further,
thus
more turning > effort is generated) and the wheels tractive authority
increases, both of which exacerbate yaw control problems > because the
pilot
has no timely way to anticipate or correct > for them. The plans
change 2
degree toe out was an effort to > counteract this but just can't
totally do
so because of the > constantly changing camber (canard flex) and wheel
tractive
authority.
So all the above being said, correcting the camber at maximum >
canard
flex toward a neutral or positive position when the > aircraft is at
gross
is a good thing. Excessive positive > camber would have little
adverse
affect on the Q-Bird since > it would only evidence when the plane is
being
turned toward > the inside wheel (with the increasing positive camber)
which
would be lifting and thus lessening it's tractive authority > and
thereby
negating any potential deleterious effect the > positive camber may
have. >
There have been more technical explanations on the > "negatives" of
negative camber on the Q-Bird, but I thought > the above may offer a
more
elementary perspective for those > of us not into the physics of the
matter.
Additionally, not all negative camber is bad, as my highway >
vehicle
has considerable OEM negative camber on the rear > wheels to enhance
stability, just depends on the application.



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http://www.quickiebuilders.org


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James Postma <james@...>
 

Larry,

I set mine to 0 degrees at gross. Solo it is about + 1 degree. It does not
have to be optimized. It just should never be negative. This procedure is
easy as I had two big guys sit in the cockpit and boresighted the axles to
each other. The only problem is getting enough room in the wheel pants for
wheels and brakes, and then realigning the brakes. I had to respace the
wheels. Using the smaller original tires makes it easier to find the space.
I am considering breaking the wheel pants from the canard and setting them
at 0 degrees on my next wheel alinement. If you are still building your
bird do set the wheel pants at + 3 degrees and they will be 0 degrees at
full gross. School of hard knocks here and verified by theory and research.
If I could write the equations in LaPlace form I could draw the stability
diagram, but I am way past doing masters degrees so please please guys stop
hashing this one and like Nike says JUST DO IT!!! The school of hard knocks
includes one broken LS-1 spar. That's a hard knock. There are many others.

James Postma
Q2 Revmaster N145EX
Q2 Revmaster with LS-1
Q200 N8427
Steilacoom, Washington
(253) 584-1182 9:00 to 8:00 PDT
May your header tank be always full and your wings right side up.

----- Original Message -----
From: "larry severson" <larry2@...>
To: <Q-LIST@...>
Sent: Sunday, June 26, 2005 8:11 PM
Subject: Re: [Q-LIST] Re: Just Another Thought on Wheel Camber



Negative camber (on the main gear of a taildragger) is destabilizing.
Positive camber is stabilizing. Positive camber
will not "transfer the controllability problem to a higher speed regime."
I stand corrected. How much positive camber should the wheels have at
rest?

Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...





Quickie Builders Association WEB site
http://www.quickiebuilders.org


Yahoo! Groups Links







Letempt, Jeffrey MR <jeffrey.letempt@...>
 

Larry,

Actually there have been several excellent responses to my Tri-Q questions
recently. Some have been off-list responses (3 I think), but most have been
on-list.

Jeff

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...]On Behalf Of
larry severson
Sent: Sunday, June 26, 2005 9:56 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: Just Another Thought on Wheel Camber


At 05:22 PM 6/26/2005 +0000, you wrote:

Get a Tri Gear and forget about it. ;o)
Bruce Crain
N96BJ
I have seen requests for information on the conversion. I have never seen a
response.


Larry Severson
Fountain Valley, CA 92708
(714) 968-9852
larry2@...