Flight control assemblies

[142YX]

Thought I would start up a thread on the flight control system assemblies as i don't see much guidance in the plans and as i am discovering, there are lots of questions to answer.

I started by putting the major components within the control stick and Waiex tail mixer assemblies together and immediately ran into a problem.. the bushings called out in the blueprints did not fit over the powder coated rods. I did not want to ream the bushings out to fit over the diameter of the powder coat as i just felt that was the wrong thing to do. I used the blowtorch method that John Monnett demonstrates in this video and it worked very easily:


http://link.brightcove.com/services/pla ... 1439759001

here is first attempt at this process:



wait until the powder coat starts to bubble



and then it comes right off with a wire brush



after that i cleaned the rods with scotch bright to until they shined. after this i found the bearings to have a nice press fit over the rods. (in the below photo the left two have been fully prepared, the right still needs scotch bright)



I didn't want to re-paint, as that would make disassembly in the future (if i ever need to) a royal pain.. so for corrosion protection, i chose to go with a black oxide (took black, gun blueing.. same thing) passivation protection layer.



After thoroughly cleaning with denatured alcohol, the bluing went on very easily and very quickly. After 30 seconds, you rinse with water.. thats it! I might add that the bluing itself does not provide a tremendous amount of corrosion protection, but seeing as how these are moving assemblies and will be well greased, i am not worried about them.



Here are the final results. I think the only tricky aspect of the bluing is getting a consistent color.. perhaps a gunsmith with a lot of experience would do better. But seeing as how i wasn't doing this for looks i was ok with the outcome.



Bearings being installed.. perfect light press fit that went on with a few taps of the mallet.



I am very happy with these results and would recommend it to anyone who hasn't made up their mind yet.. the entire process probably took me about 3 hours including the learning curve. But i am very curious how other people have done this seeing as how there are basically no instructions on what to do within the prints.

[142YX]

In order to hold the two "Horn Assemblies" in place, perfectly perpendicular with one another i cut a piece of MDF to the perfect length and held it in place with a wrap of fiberglass strapping tape. I started off with the piece a tad too long and carefully shaved it off on the miter saw until it was just perfect. On my assembly, the length ended up being 15 and 1/4 inches





This held things in place very well while the control stick link was drilled to maintain perpendicularity.

However, i have now encountered question #2.. the control stick link hits the trim spring tab before the roll stops hit the frame (in both directions) and this cant be right:


Did this happen to anybody else? what did you do? i have emailed Kerry about it and ill post here what he says.

[N111YX]

Let me first say that I enjoy these pics. Takes me back to the old building days... :D

As for the powdercoated tubing, I removed the coating with sandpaper (I did not know about the blowtorch method) and when the assembly was put back together, I taped over the bearings and gave the bare tubing a shot of spray paint. Your method looks nice.

Regarding the control assembly, I love the idea of the wood block to help make it perpendicular...wish I had thought of it... :oops: . Not sure about the contact. Mine did not have that problem. The next time the seat is out, I'll see how close it is.

I failed to get pictures of my fuel system over the weekend when I did an oil change. I TWICE though about getting the camera out but before I could I either cut my hand on something then had some visitors pop in causing me to forget. However, I plan to do some winter maintneance soon and I'll try to get some pics...

[142YX]

Kerry got back to me about the contacting control stick link:

There is a very high likelihood neither of those contact points will be an
issue once your aircraft is rigged. The aileron bellcranks have their own
stops built in and these often come in to play before the ones on the
sticks.

We recommend you continue with your build and if those contact prevents you
from properly rigging your ailerons we can solve that problem then.

I think this is reasonable.. i would expect any flight control system to bottom out at the surface, before the control in the cockpit.. safer design that way.

[N111YX]

Hmmm. That answer seems odd to me. I can't recall hard stops in the bellcrank area. Also, if the stop is not in the control stick area, would the pilot not be tranferring lot's of force throughout the system counterring a "stop" that occurs way out on the wings...?

[142YX]

My understanding of reversible flight control systems is that you always want to be at your limit of travel at the control surface.. with a little bit of motion left at the point of input (control stick) so that if something goes wrong for whatever reason.. you have a little bit of margin on your control authority to muscle it to the ground. Having the limit hit at the stick first, with some margin left at the control surface would not do you any good if some in-flight failure resulted in a loss of control authority. Hopefully the system has been sized so that maximum pilot effort will not break anything.

There are some stops on the aileron bell-cranks in the wing.. that little piece of phenolic that is sandwiched between the two aluminum brackets (i can grab a photo tonight) i always assumed to be a limit stop. There is only a stop in one direction, because the other aileron will stop in the other direction. And the ribs are re-enforced at the bell crank location with those back side stiffeners that are riveted to the wing skin. The question left to answer is if that stop is hit before i run in to my stick assembly clearance issue, but i wont know that until i have the whole system put together...

[N111YX]

Interesting. I never thought of the phenolic bits as stops but rather mere spacers. Just going from memory, I would think that the travel of the bellcrank would be extreme to make contact...

[N111YX]

Well, here are mine. I see the stop feature now... :)

[sonex892]

Interesting. I never thought of the phenolic bits as stops but rather mere spacers. Just going from memory, I would think that the travel of the bellcrank would be extreme to make contact...

The reason we would presume they are only spacers is because they are only referred to in the plans as spacers. Just re-adjusted my ailerons yesterday and couldnt get the bellcrank to bottom out on the spacers, or stops any way :cry:

Kip you mentioned earlier of using a taper pin instead of the bolt in the joystick mount. My joystick has just gotten sloppy again so I plan on doing the same. Did you use #2 or # 3 taper pin? I'm thinking of going #3.

Steve 892

[N111YX]

I don't recall the exact size pin, Steve. I have the benefit of living close to Aircraft Spruce where I can handle stuff like that in person to see what works. I think the catalogs have some good diagrams with dimensions along the pin so maybe that will work for you. We're talking about replacing an AN-4 bolt, right? It does get rid of that slop.... :)

Interesting. I never thought of the phenolic bits as stops but rather mere spacers. Just going from memory, I would think that the travel of the bellcrank would be extreme to make contact...

The reason we would presume they are only spacers is because they are only referred to in the plans as spacers. Just re-adjusted my ailerons yesterday and couldnt get the bellcrank to bottom out on the spacers, or stops any way :cry:

Kip you mentioned earlier of using a taper pin instead of the bolt in the joystick mount. My joystick has just gotten sloppy again so I plan on doing the same. Did you use #2 or # 3 taper pin? I'm thinking of going #3.

Steve 892