Pick your brains?

On Thu, 9 Jul 2009 09:50:37 -0700 (PDT), "
wrote:

http://www.eaach1.org/Design/comm6v1-1R4.pdf

Subject at hand: Landing gear design.

Article in above link pretty much puts into words my understanding of
why tail draggers do what they do. I've been thinking about an
original design for cheap one man flying (OK, lots of borrowed stuff
put together in my own unique way) and one of the little problems I
keep coming up with is cross wind control. Around here if it won't
land in a 10 Knot (gusting 30) side wind it's a fair weather toy.

For structural and weigh reasons a conventional 2 up front gear would
work best, but as we all know it isn't the best choice for low time
modern pilots, or cross wind conditions. A simple solution is a
castering main gear similar to John Moody's as used on the Easy
Riser. The problem then becomes one of ground handling due to lack of
directional control with respect to the ground. Complexity rules out
a fixed tail and steering main gear.

2 solutions:

1) Angle the axis of the castoring main gear so that the weight of
the craft tends to align the casters with the axis of the plane, or
use a locking, maybe semi locking as used in the nose gear of the
BD-5, castoring main gear. One could then use a conventional steering
tail wheel.

2) Pure differential braking in combination with a negative king
pin inclination - no lock or de-tent on main gear.

I'm open to all ideas and references to other planes that have used
similar gear - there must be some somewhere?

I have not had the option of examining an Ercoupe gear so any links to
pics/parts manuals would be appreciated. The B-52 gear is not under
consideration.................... :-)
======================
Leon McAtee

I have a 25 year old W8 tailwind.
this can be landed in conditions with the windsock rigid across the
strip. this seems to be what you are attempting.

the key is the tailwheel which has a solid link from the rudder
bellcrank to the tailwheel control lug. any time you have the wheel (a
4" homebuilders solid wheel from aircraft spruce) on the ground you
can steer the tail into position. the bellcrank at the rudder is half
the distance out from centre that the tailwheel control lug is.
the other requirement is that the neutral position of the tailwheel
matches the neutral position of the rudder.

the toe in/toe out argument regarding the mains is resolved by
considering the dynamics occurring during a swing during landing.
if you are turning to the right then the aircraft inertia is thrown to
the outside of the turn which presses the left wheel harder onto the
pavement. if this wheel at that moment is pointing in the direction of
travel then it contributes no additional forces that you have to get
under control. for this reason the undercarriage leg should flex into
a toe out position. it is irrelevant what the static parked wheel
position is within reason.

understand Wittman's W8 undercarriage and you will have your solution.
Stealth Pilot