Model IV Rudder Pedals

[Danzer1]

Larry, I am not aware of any failures, cracking, Service Bulletins or Service Letters regarding failures or cracking at the rudder cable attach tube. The known location is at the bottom of the rudder pedal vertical tube where it is welded to the horizontal bottom tube. It is my understanding, those are the locations reinforced. Can you point me to your information please?

As a curiosity, does anyone have a guess, how hard you'd have to stomp on left rudder to tear the vertical rudder tube metal? The picture shows the weld intact, but the surrounding metal torn.

Thanks, Greg

[tomec]

they were flying it this way.

[Danzer1]

To be honest, I was a little concerned when he said you would be flying it home. Glad you did a complete inspection and decided on the trailer.

Surprised that didn't get caught in the "recent annual" or when "gone through from stem to stern by an IA" (as described). Not to mention this statement: "I am confident that he will have no trouble because other than cosmetics, the plane is in very good shape". Amazing!

On another note: In the picture of the tailwheel - what is all the white "gunk" on the tailwheel bracket?

Greg

[Dave F]

Larry, I am not aware of any failures, cracking, Service Bulletins or Service Letters regarding failures or cracking at the rudder cable attach tube. The known location is at the bottom of the rudder pedal vertical tube where it is welded to the horizontal torque tube. It is my understanding, those are the locations reinforced. Can you point me to your information please?

As a curiosity, does anyone have a guess, how hard you'd have to stomp on left rudder to tear the vertical rudder tube metal? The picture shows the weld intact, but the surrounding metal torn.

Thanks, Greg

4130 tube likely a little brittle due to quick cooling
TIG torch only heats the direct welded area and the are next to the weld has failed. Normalizing can help alleviate this.

[Slyfox]

actually the tube there is thin, just like the motor mount. there is a kit for reinforcement or you can replace the whole pedal.

[Av8r3400]

That's right, Slyfox. These rudder tubes are all made of .035" wall tube. The new, revised parts have finger-strapping on the vertical elements and reinforcing gussets on the cable attaching arms.

I chose to do something completely different on my project plane. I built my own rudder peddles based off the Wag-a-bond design.

[HighWing]

I built two Model IVs and while building the first one there was talk on the Kitfox List about the possibility of failure of the torque tube. As I recall the discussion started after a guy had his fail on short final. Lots of discussion on the welds and hardening of the metal as Dave suggests, but I seem to remember that most of the stones were cast at Mig rather than Tig. Most guys were adding gussets to the four pedal tubes and the rudder arms. I did it on the first one during the build - 1993 kit and the original owner did it on his 1992 kit before I took over for my second build.

Edit: I talked to my best Kitfox Bud last evening and asked him about the rudder pedal torque tube and he has never done the mod. He has owned several Kitfoxes including four Model IVs. So I guess it is us belt and suspenders guys that did the mods

[Av8r3400]

Forgive me, I don't want to be accused of over moderating, but I started a new thread and moved these posts for the rudder pedal conversation.

We were all kind of hijacking Tomec's new plane picture thread…

[GWright6970]

For future searches on this topic, this is a picture of the KF factory reinforcing kit I installed on my KF IV-1200 prior to painting, so one can see the reinforcing pieces being described. There are also tubes that one cuts and installs in the torque tube, that these plates are riveted to. The instructions say to cut the inserted tubes "lengthwise one hack saw blade width." This is NOT enough to compress the tubes and insert them, even with a hammer. Cut the tube at least two hacksaw blade widths... it will then be tight, and at able to be tapped in without messing up the end.

[Danzer1]

Guys,

As mentioned in the 1st post - I am aware of and understand the reinforcement at the base of the tubes. Maybe I didn't ask it right. The picture in the 2nd post shows tearing at the outboard rudder cable attach tube. Is that location also reinforced with the kit? And is that location reinforced if the new rudder assembly were purchased? Those are the questions here.

Grovers picture shows outboard brakes reinforced (it appears), which the plane tomec bought I can't see - it has outboard rudder cable attach tubes. That appears to be a failure point, that if not currently being addressed, maybe deserves some attention by series 4 (and possibly earlier version) owners.

Thanks, Greg