SkyBound

Hi,

I need some advise. I am installing my first pull-pull rudder system. I am installing it in the new S2B Pitts from Cermark.
I am also splitting the elevators.

From what I gather, the optimal set up would include a straight shot from the servo arm/wheel to the horn on the rudder with no sheathing on the wire. And from what I usually see, the placement is always at the bottom of the rudder.

But I have also seen instances where the wire has been routed through a pushrod tube.

My situation is such that I have to clear a servo on each side of the fuse at the rear, and just infront of the stab.
The only straight shot I have is either 1) too low.. I would have to mount the horn on the rudder within a 1/4 of an inch of the bottom, or 2) I could install the servo relatively higher than the horn and angle up to the servo.

Here are my questions:
1) Is it a must that the wire not be in a sheath?
2) Does it hurt to angle the wire, instead of staying relatively parallel to the fuse?
3) Does the placement of the rudder horn have to be at the bottom of the rudder?
4) If not, would it hurt, or otherwise be unhealthy to fashion a mount point on the rudder that was halfway up the rudder and the wires exited the fuse above and foward of the stab.?

That's it.. appreciate the feedback everyone.

SkyBound

Jim Branaum

My Feedback: (3)

Several points of interest for you.

The best place for the wires to attach to horns on a pull system for a tail dragger is always the lowest you can get a good solid point on the rudder. The reason for this is that the flatter the angle between your rudder horns and tail wheel, the more effective the ground steering will be.

You CAN use sheathing, but make sure you use some sort of ferrules to protect the cable if you are using kevlar. It is important that the width of the horn hook up on the rudder be the same as on the servo (or tiller bar). Otherwise you may have problems with returning to center. It is also important that the hook point be as close to the hinge line in line up as possible to avoid having one taut line and one loose line.

Do a search for "Ackerman" for discussions about pull pull systems.

Good luck

iflyrc24

My Feedback: (5)

Skybound
The rudder cables on my Challenge II, Explorer, Typhoon 909, and Viper 2m all come out above the stab. All the tail wheels were steered by the bottom of the rudder. I had no problems with any of them in the rudder, tail wheel area.

DEG

SkyBound

Thanks for the info fellas,

I am using the leaf spring tailwheel (medium) on this page http://www.davepatrickmodels.com/tea.../tailwheel.htm.

What is normaly done with the steering of the tailwheel. It looks like there is an arm on this one with holes in it. Am I supposed to connect that somehow to the rudder... or rudder wire?

SB

Jim Branaum

My Feedback: (3)

What IFLYRC24 suggests is not wrong, but it does leave you to figure out how to transfer the steering controls to the tail wheel. This is my observation only, as each of us does things our own way.

As for the Dave Patrick tail wheel assembly, I don't know how it is designed to be hooked up. Normally I try to tie the pull pull cables to the same holes I drive the tail wheel from. I think DuBro has a tail wheel that has a spring loaded wire you bury in the rudder to transfer the control to the wheel, but it may take a different type of mount to be used.

Good luck.

SkyBound

Jim, thanks again.

Do you know if it would hurt to run the wires from the bottom of the rudder at an angle up to... say.. the cockpit area. Does it hurt to pull on the rudder at an angle?

Jim Branaum

My Feedback: (3)

No, it does NOT matter at all.

You can run them in a loop (inside a carrier that is) around the fuselage as long as the drive end and driven end widths are the same. The force is applied to the horn which transfers it to the rudder. As long as the horn is not being pulled off the rudder, lots and lots of wild things are possible. I said possible, not recommended!

Good luck

SkyBound

That's great news.. that means I have my problem solved.

I can run the cables in a straight line from the cockpit area at an angle which carries them over the servos and straight to the proper mount point on the rudder... no sheaths, and horn is where is should be.. so life is good.

Thanks a million Jim

Jim Branaum

My Feedback: (3)

Great. I am glad this works out for you. If you are using Kevlar, make sure that it does NOT rub on anything. For that I use a small section of medium golden rod tubing with ferrules on both sides as the carry through. The carry through protects the Kevlar from the fuselage sides and the ferrules protect it from the tube ends. I use servo mounting brass as ferrules and glue them to the tubing.

carlbecker

My Feedback: (3)

Vibrating kevlar will cut most anything just like a saw. Don't ask how I know. I would make sure that the horns, lines and servo are in the same plane if not using a channel or pulleys in the path. Lateral forces could cause deflection and possible failure. Do keep the distance between hookups the same on horns and servo. It matters.

Carl

SkyBound

Thanks for the feedback guys.

I am not using Kevlar.... I am using DuBro heavy duty pull-pull system

Carl,

I plan on keeping the servo, cables, and horns in the same plane (no carry through), but, that plane will not be parallel with the bottom of the fuse., it will be rising at a constant angle towards the servo... do you see any problems with this set up. My only concern is that the upward pull on the rudder will adversely effect the performance of the rudder.