taildragger toe-in vs toe-out AGAIN

On Fri, 14 Nov 2003 19:12:31 -0600, - Barnyard BOb -
wrote:

On 15 Nov 2003 00:22:09 GMT, (JFLEISC) wrote:

There's lots of
emperical and experiential opinions out there, anybody with some more
factual answers to the argument?

I've pondered this thing myself. Problem with tail draggers (actually a
characteristic of aircraft and their need to have flexible gear way out on
spindly aerodynamic legs) is that toe out could change to toe in depending on
the load. This also changes during the transition from ground to flight. Worse
yet (the big problem with my plane) is the toe change as I bring the tail up on
take off or transition down during landing. Suffice to unscientificlly say that
20 years in the automotive alignment business has shown me that cars with toe
out tend to be a bit more twitchy than those with toe in. Have no idea if that
translates to aircraft because taildragger pilots EXPECT the plane to try to
swap ends.

Jim
+++++++++++++++++++++++

TOE IN is a NO-NO for tail draggers.
Just the reverse of cars.

And many cars actually DO have a toe out spec.
The ideal is for the wheels to roll 100% straight down the road.
Depending on steering geometry, they will try to toe out, or in. The
spec is to set them toed in if they tend to toe out, and out if they
tend to toe in, so that the natural forces pull the wheels towards the
straight ahead position. GENERALLY, vehicles with front wheel drive
tend to have toe out specs. ( Austin mini (old) was 0.062 inch toe
out) - but more and more you are seeing spec of 0 +/-.
The position of the tie rod, either ahead of or behind the steering
axis had some effect, as does the position of the intersection between
the KPI and the wheel centerline (camber).

Positive camber contributes to a toe-out tendancy ( that's why cars
tend to pull to the side with the most positive camber) (also think
about the handling of a bicycle)and Negative caster has the same
tendancy.
On an aircraft landing gear, the camber is self evident - and the
"effective" camber changes with load, and is effected by "unballanced"
landings (one wheel first). If the landing gear has "caster" it
changes between tail-up and tail-down attitudes. The different
combinations of uneven loading and landing attitudes will all effect
the "toe" behaviour of the wheel - so it is dangerous to make a
statement that either toe out or toe in is NECESSARILY more desirable
on a particular plane.


Read the archives.
This has been beaten to death.
Many times.


Barnyard BOb -