Anyone Ever Replace a Pull-Pull Cable With a Rod and Clevis?

[Rocketeer]

Greetings Gang,

I have a 1600mm warbird that is a tail dragger and uses a Pull-Pull wire cable system and servo for steering. I really don't like this system. I have heard of folks who have converted the wire cable system to a typical servo/rod and clevis arrangement.

Has anyone ever done this to any of their planes? Doesn't seem like it would be all that difficult to do, but I've never attempted it.

Thanks in advance,

Bill L.
in Okla.

[Guest]

Re: Anyone Ever Replace a Pull-Pull Cable With a Rod and Clevis?

Hi Bill, the current configuration of your pull-pull system will determine how easy it is to convert to a rod/clevis setup. Generally it is simply a matter of replacing the wires with control rods, but things can get complicated if your steering arm is not set up for a hard setup.

In many pull-pull arrangements, the wires go slack when the strut is retracted, so the rudder/steering servo moves inside the airplane without any load. When the strut is deployed, the wires become tense, thus giving the servo authority to move the strut. Study how control rod setups use a different steering arm design, to allow the control rod to slide downwards as the trunion pivots. This maintains proper geometry for the solid rod, without causing the servo or retract to bind. Adapt that design to your existing pull-pull setup, and the conversion should be easy from there.

Best of luck,
Alpha

[Rocketeer]

Re: Anyone Ever Replace a Pull-Pull Cable With a Rod and Clevis?

Greetings Alpha,

I appreciate the input and I have been, as you recommended, surveying various systems on other models in an effort to investigate a transistion method.

Ascertaining the appropriate geometry for both rotational angles was a concern as in other systems it appears that one rotarion would provide greater response than the other. i.e., greater ability to steer left than right.

Clear Skies

Bill L.
in Okla.

[RonF]

Re: Anyone Ever Replace a Pull-Pull Cable With a Rod and Clevis?

I've actually prefer pull-pull. Since this is a tail dragger, it could be a problem if it is a retractable tail wheel. If you don't use a tail wheel assembly designed for a single pushrod, you could bind the servo when the wheel is retracted. If it doesn't retract, then just replacing the cables with thin music wire could work. Study what you got now and see if you can just "fix" the slop issue. Alpha has good advice so take your time and see.

[Rocketeer]

Re: Anyone Ever Replace a Pull-Pull Cable With a Rod and Clevis?

Greetings Ron,

Thanks for your input.

It is indeed a retractable tail wheel.
Also, the main issue is slop in the wire cables.

As recommended, I have re-evaluated the situation and I've decided that since that was my first ever attempt at a pull-pull system, I'll chalk it up to experience and try again with new wires.

Clear Skies

Bill L.
in Okla.