Control hornes

[dheaton]

I am building this plane and am ready to install the push rods and control horns. I need some help on how to put the horn on the elevator. The rudder I can do just fine. I have built according to the plans but it doesn't give me an idea on the elevator.

This is a photo of under the plane. You can see that the rudder will work just fine but I can not get the wire to bend enough for the elevator.

[DHC Beaver]

Your best solution would be to re-route the pushrod,so it comes out of the fuselage further forward.This will allow some flex in the pushrod.

[dgjessing]

They both look too tight... Don't forget that there needs to be some flexing possible in the rod as the horn goes through it's rotation.

[dheaton]

Well perhaps I need to rip the push rods clear out and start over. They are in according to the plans though.

[Henry Sistrunk]

Was this built from a kit or is it an ARF?

[kyleservicetech]

Originally Posted by dheaton

Well perhaps I need to rip the push rods clear out and start over. They are in according to the plans though.

Yikes
If this is per the plans, then the plans are wrong! As dgjessing points out, as the elevator horn goes through its rotation, you've got to allow for the pushrod moving in and out following the rotation of the elevator horn.

If not allowed for, you are going to get binding, and a lot of it. Typically the exit point for the elevator/rudder push rods will be about 3 or 4 inches ahead of the surface to be controlled. By the way, the same applies to the rudder push rod.

[dheaton]

It was from a kit

Originally Posted by Henry Sistrunk

Was this built from a kit or is it an ARF?

[hayofstacks]

A lot of the times, the pushrod tubes bend and cross from one side to the other, giving you a sharper angle for the pushrods to exit through. Rather then being in a straight line, it should be in more or a "c" shape or even cross in an x pattern, if that makes sense.

If you have thick enough wire, you could put a bend in the push rod after it exits. This won't be ideal, because it will give more room for the rod to flex, and another bend. I would see if you can pull it out abit further back in the fuse, like everyone else said.

[solentlife]

As others ... your pushrods are far too rear for good alignment - as you found out. Rudders are OK as the horn is near enough centre-line.

As Hay says - one of the best ways to get a better angle is tio cross the pushrods inside fuselage in an X .. usually the elelvator rod exits fuselage higher and more forward than the rudder rod - allows the X to work without rods rubbing or conflict.

You could solve this without any cutting - by using flexible snakes such as Sullivan or Bowden ... which is flexible nylon rod in a tube. It's an excellent way to solve routeing problems.

Another way is to go to your LHS and buy a hinged control arm unit. These are a long arm with pin at centre. The pin pivots in a plastic holder that is glued into the fuselage.... AFTER internal push rod is connected to the inner part of the arm - by Z bend ...... the outer part of the arm then has a short control rod to the surface. This would solve your problem 100% without need to cut fuselage ... they also prevent introduction of flexing from bends etc.

Nigel

[Henry Sistrunk]

Yes, Remove the pushrods and install them so that they look more like this.
Henry

[dheaton]

Thanks for all the help guys, I appreciate it very much.

[solentlife]

I have a habit fr9om old days ...

I build a model and part way through construction when fuselage is near built - I lay a straight edge on top to see the line of pushrod ... this then tells me where to exit fuselage at back end etc. Simple - but avoids the OP problem.

Nigel

PS - Most models now I build with servos mounted at back close to surface not needing pushrods anymore. Why ? In the old days - servos were heavy beefy affairs .. now we have servos that are a lot lighter, powerful, faster etc. With todays radios allowing mixing etc. - whats the need to all the hassle ?