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.:eek:

[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

[GWright6970]

Greg,
Yes, the picture I posted shows that the "attachment point arm" that the rudder cables and the springs anchoring them to the firewall ARE part of the reinforcing kit plates. This is the part that appears to have broken in your pictures, so it is addressed by this kit. (Obviously, there is NO internal tubing added at this point, like there is to the torque tubes.) The factory reinforcing plates are molded to fit the curve of the tubes; are stout pieces of steel, and should be a proper strength addition.

[av8rps]

For anyone questioning the need to reinforce their rudder pedals - DON'T QUESTION IT. JUST DO IT!

I say this based on my experience with a rudder pedal failure once.

My story goes; I once had a stainless nicopress fitting slip off of a rudder pedal cable (stainless requires a special tool to crimp) while test flying a friends' recently purchased Avid Flyer. It happened just as I was starting my takeoff run, and then just as I was about to rotate, a severe crosswind gust forced my instantaneous reaction to apply right rudder. I heard a loud bang from the rudder pedal hitting the firewall, quickly realizing that I had lost my rudder. The next 5 or 10 seconds was more than exciting as I heard the tires screeching across the pavement in a full sideways skid as I was headed for a runway light. But I got really lucky as I had just enough speed to have enough elevator effectiveness left to allow me to "Hop" over the light, and enough aileron to keep the wing from diving into the dirt and pavement as I did the tightest ground loop in the dirt I have ever seen. Amazingly, the only damage to the Avid was dirt being packed into the open end of the open flaperon tube. Whew!

After I gathered my senses, I really thought about what would have happened had I actually flew away rather than pulling the power. Anyone that has ever flown an early Kitfox, or an Avid knows that all of these airplanes have an incredible amount of adverse yaw. Thinking about that more, I realized I was EXTREMELY lucky not have have flown away after that nicopress failed. I've been flying these little planes since 1986, but I doubt I could have gotten that plane back on the ground in one piece without rudder. The adverse yaw would just be too severe to fly even around the pattern in my opinion. I don't believe you could control the airplane without rudder control. At best you would have to land in an incredible side slip, which would be interesting to say the least.

Even though my situation was not caused by a broken rudder pedal, a failed rudder pedal would likely be just as bad. SO guys and gals, if you don't have reinforced rudder pedals, REINFORCE THEM. You never know when that day comes that you have to stomp on that rudder pedal, and the pedal fails. Unless the big guy is really looking out for you, it is likely to ruin your day... so be proactive and install the kit. It's a lot easier and less expensive than fixing your entire airplane.

[tomec]

In all fairness to the inspector, the inspection was done in Aug. then the new owner took TG lessons in it . He probablely broke the pedal early in his traing and then was not able to control after so sold plane. The break has no rust.

[t j]

I think the rudder pedal torque tube gets over stressed when someone presses on both break pedals hard...like when doing a run up.

I had a welder put gussets on the horizontal to vertical tube junction and straps around the cable arms to vertical tubes. Now having seen the reinforcing kit and explanation shown above by GW, if I had it to do again, I would get that kit.

[GWright6970]

Tom,
Excellent point on how they may get broken... also, to add to your list of causes, how about when you find that you are slumping down in the seat, and then push yourself back up, by bracing your feet against the rudder pedals?

I remember catching myself doing that in my Cessna 172, and saying never to do that again!!

[Dravenelle]

can you post a picture of the torque tube upgrade
from kitfox

thank's

Dave

[Danzer1]

Post #9 this thread.

[mr bill]

The braces on the factory reinforced pedals look similar, but are welded in place. Pop rivets would not seem strong enough, but if the factory says so, it must be so. Were they also bonded?

[GWright6970]

Yes, the directions have you applying the HYSOL 9460 to all contact places, including INSIDE the torque tubes where the inserts are placed. Where possible, the metal is preped by taking it to bare metal, and cleaning these places with something like Poly Fiber C-2200 metal cleaner.

Here comes the run-on sentence:
The Outside Triangular Plates (seen in the picture) on the torque tubes are riveted through these plates, through the torque tube, and through the inserted tubes inside the torque tube to sandwich/connect them "all into one unit."

The rudder connection arms are also bedded in HYSOL, while being riveted.

The final product sure appears to be "beefed up."