Tail wheels, or is this forum really dead?

On Feb 1, 3:54*am, Stealth Pilot wrote:

I believe that the original poster has a problem but is off on the
wrong track trying to solve the problem.

I may be off on the wrong track, but don't have a problem with
'draggers, in general, or particular.

Just have the desire to tinker and see if I can improve the ground
handling a bit ....... and see if I couldn't stir up a bit of
discussion on the group.

One goal accomplished.

Those that think a "negative caster" tail wheel would just flop
sideways, or even swap ends if not restrained are forgetting about
choosing a pivot angle to match. With the proper pivot angle and
weight on the tail the system can be stable up to a point.

For an analogy consider flying a plane that has it's CG behind the
neutral point and an all flying horizontal stab. This is essentially
what a tail dragger is on the ground.. Move the pivot of the stab
back behind the aerodynamic center and add an anti servo tab linked to
a mass. The whole system will never be stable, but can be self
stabilizing with in a narrow range.
======================
Leon

On Mon, 1 Feb 2010 09:26:27 -0800 (PST), "
wrote:

On Feb 1, 3:54*am, Stealth Pilot wrote:

I believe that the original poster has a problem but is off on the
wrong track trying to solve the problem.

I may be off on the wrong track, but don't have a problem with
'draggers, in general, or particular.

Just have the desire to tinker and see if I can improve the ground
handling a bit ....... and see if I couldn't stir up a bit of
discussion on the group.

One goal accomplished.

Those that think a "negative caster" tail wheel would just flop
sideways, or even swap ends if not restrained are forgetting about
choosing a pivot angle to match. With the proper pivot angle and
weight on the tail the system can be stable up to a point.

For an analogy consider flying a plane that has it's CG behind the
neutral point and an all flying horizontal stab. This is essentially
what a tail dragger is on the ground.. Move the pivot of the stab
back behind the aerodynamic center and add an anti servo tab linked to
a mass. The whole system will never be stable, but can be self
stabilizing with in a narrow range.
======================
Leon

leon
most successful tailwheels have the pivot axle vertical.
weight and cg position on a taildragger are largely irrelevant to the
tailwheel setup because they dont come into play.
what is important is that you apply full aft stick once the touchdown
has been effected. it is the download from the elevator that gives the
tailwheel its incredible authority on the ground.

be very careful here with your experimentation. this is one area of
aircraft setup that can work well or work absolutely horribly with not
much difference apparent between either state. the rudder shimmy
problem I mentioned before occurred with just one spurious turn of a
1/4 x 28 thread on the link arm.

one of the causes of poor tailwheel performance is the slop in the
attachment of the tailspring to the fuselage. on a lot of aircraft
with poor tailwheel control if you push the wing tip up and down you
can see quite a lot of movement in the tailwheel because the whole
setup is actually quite loose. the spring should be rock solid with
wing wiggle.

I'd make the point as well that people focus on the taildragger as
having groundloop tendencies. if you want to see a real groundloop
just wheelbarrow a trike on on its nosewheel without putting the mains
down. that can be tinsel ball stuff. I know of one commercial pilot
who gave up flying after wheelbarrowing and groundlooping a Cherokee
140.

enjoy the experimenting.
Stealth Pilot

On Feb 1, 10:26 am, "
wrote:

Those that think a "negative caster" tail wheel would just flop
sideways, or even swap ends if not restrained are forgetting about
choosing a pivot angle to match. With the proper pivot angle and
weight on the tail the system can be stable up to a point.

The only "stable" arrangement is tire/surface contact behind the pivot
axis/surface intersection point, with the pivot vertical or angled top-
back a little. And that stable arrangement applies to both trike and
tailwheels. If you photograph a trike from the side, as I have done,
and draw a line through the nose strut axis, as I have done, you will
see that the pivot axis, being angled, intersects the surface ahead of
the center of the tread area. It's the same principle found on a
bicycle. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Furthermore, neither arrangement will offer any stability if the tail
is off the ground. A taildragger is still a taildragger even when it's
moving with the tail up a bit, and the pilot MUST control it with his
feet. Every so often someone tries to tame the taildragger by
proposing complex solutions, and it could be done with computers and
servos and a whole lot of stuff, but it would be about as much fun and
take about the same skill as driving a kiddy car.

Dan

On Feb 2, 7:15*pm, wrote:
.. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. Have you ever used a measuring
wheel?
===================
Leon

wrote in message
...
On Feb 2, 7:15 pm, wrote:
. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. Have you ever used a measuring
wheel?

Yes I have; used them for several decades and many miles of measuring. They are
very unstable (but very manuverable) if you use them in the forward direction.
For long straight measurements, I always trailed them.

Vaughn

On Wed, 3 Feb 2010 07:48:26 -0800 (PST), "
wrote:

On Feb 2, 7:15Â*pm, wrote:
. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. Have you ever used a measuring
wheel?
===================
Leon
Virtually every distance measuring wheel available on the market
today has the pivot point well ahead of the patch.

The lufkin PSMW38 does. Northern's rotatape does. So does every other
RolaTape listed. DriVall Fencing's units do. The DuraWheel does. So
does the TruMeter. So does the Gill.
And EVERY measuring wheel I've ever seen, unless you DRAG it instead
of pushing it. And dragging is not accurate because you unload the
wheel, rather than loading it, over obstructions.

On Feb 3, 7:27*pm, wrote:
On Wed, 3 Feb 2010 07:48:26 -0800 (PST), "

wrote:
On Feb 2, 7:15*pm, wrote:
. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. *Have you ever used a measuring
wheel?
===================
Leon

*Virtually every distance measuring wheel available on the market
today has the pivot point well ahead of the patch.

The lufkin PSMW38 does. Northern's rotatape does. So does every other
RolaTape listed. DriVall Fencing's units do. *The DuraWheel does. So
does the TruMeter. So does the Gill.
And EVERY measuring wheel I've ever seen, unless you DRAG it instead
of pushing it. And dragging is not accurate because you unload the
wheel, rather than loading it, over obstructions.

Let's talk apples to apples here. The measuring wheel is a hand-
held device and will pivot both along the handle axis in your hand,
and swing side-to-side. We have TWO axes of motion here, where there's
only one for a tailwheel or nosewheel. It's not the same effect at
all. If you were able to make your wrist rigid so that the side-to-
side swing was impossible, your instability would disappear.

Dan

On Thu, 4 Feb 2010 12:04:48 -0800 (PST),
wrote:

On Feb 3, 7:27Â*pm, wrote:
On Wed, 3 Feb 2010 07:48:26 -0800 (PST), "

wrote:
On Feb 2, 7:15Â*pm, wrote:
. Anytime you try to put the tread contact ahead of the pivot
you are creating an unstable arrangement that simply won't work.

Not a completely true statement. Â*Have you ever used a measuring
wheel?
===================
Leon

Â*Virtually every distance measuring wheel available on the market
today has the pivot point well ahead of the patch.

The lufkin PSMW38 does. Northern's rotatape does. So does every other
RolaTape listed. DriVall Fencing's units do. Â*The DuraWheel does. So
does the TruMeter. So does the Gill.
And EVERY measuring wheel I've ever seen, unless you DRAG it instead
of pushing it. And dragging is not accurate because you unload the
wheel, rather than loading it, over obstructions.

Let's talk apples to apples here. The measuring wheel is a hand-
held device and will pivot both along the handle axis in your hand,
and swing side-to-side. We have TWO axes of motion here, where there's
only one for a tailwheel or nosewheel. It's not the same effect at
all. If you were able to make your wrist rigid so that the side-to-
side swing was impossible, your instability would disappear.

Dan
Who said anything about instability? Not me. Properly handled, pushing
a measuring wheel is dead easy.. I'm saying the measuring wheels and
tail-wheels - and bycycles - are all set up the same way FOR
stability.