What are the criteria / requirements for building a pull pull steering system?

Keep control arms at both ends the same length if possible or one side becomes loose hence play in the steering. Use good cables and slop free linkage

I try to do exactly what Kelly says regarding lengths of the control arms.

I usually run a separate bellcrank so the tension on the steering cables is not dragging on the servo shaft,
the servo drives the bellcrank with a separate link.

There's a very fine line between adequate tension on the cables & stopping the retract from locking down,
a LITTLE slack is needed. If the nosewheel folds your just a passenger. As the wheel retracts the cables
go slack, a cable tie used as a tensioner or a couple of light rubber bands to maintain some tension on the
cables & prevent them catching on things in the model.

John.

Kelly and John pretty well summed it up.
I will add that I also prefer to buy my wire cable from a quality fishing supply shop. You can get some really good plastic coated steel trace which is a lot stronger than other wire brand you are going to pick up from your local hobby shop. I also use mono leader in the 60-80 pound breaking strain from fishing supply shops for my wheel steering. My opinion mono leader material will have some slight stretch which I think benafits for using as a wheel steering and you will not notice the stretch. I will however add not to use mono leader for flight surfaces as you do not want any stretch when operating these surfaces.

Here's how I setup one with retracts. Dan.

I usually cross my cables

Recently built a model that used springs in front of the retract to keep the nose wheel centered. Steering cables run through tubes on each side. As the wheel retract the springs keep the nose wheel centered. Very simple and effective.

Len, some nose gears have reversible trunnions and can be fitted with one of these in the link below. Just need to be able to turn the cylinder in the other direction so it must clear any formers. I am going to try this with a set of pro link electric gear on the ultra flash.

Best set solution is get rid of the cables if possible.


http://www.rcuniverse.com/forum/atta...1&d=1375579653

Many thanks for tips and suggestions I think Gary's suggestion is the real solution.
a special thanks to the guys 'down under'.

I don't like cables so I used the same approach as Gary. Since I couldn't buy a direct drive adapter to fit my application, I made my own by brazing a bushing to a piece of steel and cutting an opening to mount the servo. Works great.

Joe

Hi, on a Eurofighter a long while back I used a solid wire idea on the nose leg, the original link was a wire pull pull and the servo was located in the fuselage and no connected to the nose leg so you had to have long loose wire in the fuselage while retracted which could snag on deployment.

The idea was to use piano wire which did not bend but instead slid through two little wire clamps used in model kits fitted to the servo arm, when the gear was extended the wires slid through the clevis and a brass stop fitted to the end of the wires contacted the servo arm allowing the steering to be used in full, when retracted the wires simply laid flat between the nose leg and the servo.

Hope the pictures explain better..... it worked very well.



marcs

What prevents the strut from turning when the gear is up?

Also, doesn't the servo take a lot of jarring from the nose wheel hitting debris on the runway?

I guess I just don't see the point of this. Yes, pull-pull works great for precision control of the rudder. But do you really need that kind of precision on the nose wheel?

Guess it depends if you want to slalom down the patch..........