Q-46: I just bought my first model aircraft with a steerable nose gear. I’m not sure how I should hook this up so that I can steer the model while on the ground.
A-46: I recently reviewed the Hobby Lobby Bonnie 20 electric-powered
ARF advanced trainer in AMA’s new online magazine, Sport Aviator. I’ll
steal a couple photos from that article, but you might want to look it up to
obtain other ideas.
Basically, the nose-gear wire strut is held in place (usually to the firewall)
with a pair of nylon brackets. The brackets are actually bearing points that
allow the strut to rotate, which causes a steering action. A tiller arm is
installed on the strut. A wire control rod is run from that tiller arm (or
steering arm) back to the output arm of your rudder servo.
I like to use an adjustable servo output arm for this type of installation. The
wire coming from the nose-gear tiller arm is placed in the inside hole of the
servo output arm; i.e., the hole closer to the center hub of your servo output
arm.
At the outermost hole, in that same servo arm, you place a second control wire
which is routed aft, inside the fuselage, and eventually connects to the control
horn located on the movable aircraft rudder.
By having the rudder connection on the outside hole of the arm, you will obtain
a considerable amount of rudder control throw, and that is what you want. The
“inside” hole connection for the nose-gear strut is to reduce the amount
of nose-wheel steering. If you have a great deal of nose-wheel steering, you
will find it difficult to track a straight course while maneuvering your
aircraft on the ground.
The other thing you must make sure of is that the rudder and nose wheel steer in
the same direction. When you move the rudder control stick on your RC
transmitter to the right, the rudder should move for a right turn and the nose
wheel should also turn in the direction that causes a right turn. If the
directions are opposite, you will have a big problem.
The nose-wheel strut absorbs many “shock loads” while the model is taxiing
around before taking flight. Much of those loads is transmitted back to the
rudder servo and its gear train. Because of this, you are generally advised to
use a higher-output (more rugged) servo for the rudder/nose-wheel-steering
application.