On Jun 24, 10:57*am, Dan wrote:
wrote:
On Jun 24, 7:13 am, Dan wrote:
* *I'm looking for a simple design for nose wheel steering for
retractable gear. Any ideas?

Dan, U.S. Air Force, retired

Morse cables?
============
Leon McAtee

* *I came up with a fairly simple idea using hydraulics with brake
master cylinders to supply pressure. Problem is the wheel will either
still steer when retracted making for a big wheel well or any disconnect
system I can think of becomes complex beyond my pay grade.

* *I had considered cables but every sketch or model I can think of
tends to put a lot off stress on the cables or downloads tension when
retracted depending on which side of the pivot point the pulleys are.
This makes for some interesting spring configurations. If anyone has
solved that I'd like to hear what solution was derived.

* *The T bar idea Bildan suggests is interesting. I will have to do some
cogitation on that one.

Dan, U.S. Air Force, retired

The system I described is used in some nose gear retract systems.
However, it is very direct steering with no 'give'. Some systems use
springs or elastomers to provide some 'softness' to the system.

One reason for softness is crosswind landings. If you touch down with
the controls crossed, (downwind rudder and upwind aileron) the nose
wheel steering will cause the airplane to dart to the downwind side of
the runway when the nosewheel touches unless the pilot remembers to
center the rudder. Adding some torsional "give" and some caster helps
with this.

An alternative to the T-Bar is a small "rudder post" connected to the
pedals with cables. The post is directly above and in line with the
nose strut when it's extended. The nose strut makes a rotary
connection with the post as the downlock engages. Sometimes this is a
slot-and-tang or other coupling method. The slot-&-tang will have a
bull nose on the tang and "V"lead-in on the slot so it engages
smoothly even if the pedals and nose strut aren't exactly aligned at
gear extension.

Landing gear design is a tricky business and a lot of things aren't
intuitive. One of my favorite stories is the last of the tailwheel
piston fighters. Enough 20 year old 2nd Lt's ground looped these
aircraft that the designers took notice and went back to their drawing
boards (Literally).

One solution was main gear struts that rotated outboard as they were
compressed. The idea was that when a swerve leading toward a
groundloop began, you wanted to "steer into the skid" as with a car.
The rotating main struts did this aromatically as the aircraft weight
shifted to the outboard main gear, compressing the strut, hopefully
giving the 2nd Louie another few seconds to save his butt.