Flight control assemblies
Posted: Mon Dec 10, 2012 3:42 am
by 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.
Re: Flight control assemblies
Posted: Mon Dec 10, 2012 3:56 am
by 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.
Re: Flight control assemblies
Posted: Mon Dec 10, 2012 10:28 am
by N111YX
Let me first say that I enjoy these pics. Takes me back to the old building days… 
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…
Re: Flight control assemblies
Posted: Tue Dec 11, 2012 2:00 am
by 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.
Re: Flight control assemblies
Posted: Tue Dec 11, 2012 9:20 am
by 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…?
Re: Flight control assemblies
Posted: Tue Dec 11, 2012 12:01 pm
by 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…
Re: Flight control assemblies
Posted: Tue Dec 11, 2012 1:34 pm
by 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…
Re: Flight control assemblies
Posted: Tue Dec 11, 2012 1:41 pm
by N111YX
Well, here are mine. I see the stop feature now… 
Re: Flight control assemblies
Posted: Thu Dec 13, 2012 10:34 pm
by sonex892
N111YX wrote: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 
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
Re: Flight control assemblies
Posted: Thu Dec 13, 2012 10:43 pm
by 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…
sonex892 wrote:
N111YX wrote: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
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
Re: Flight control assemblies
Posted: Fri Dec 14, 2012 2:27 am
by sonex892
No worries and thanks Kip. Yes we are talking about removing the AN4 bolt in the joystick. Gee I wish I was as close to ACS as you. According to google I’m 11,850km from my nearest ACS outlet, thats direct.
The # 2 taper pin will be best with dimensions slightly larger than the 1/4" bolt. I’ll order the #2 reamer, a pin or two and also some chromoly to remake the part if needed.
Steve 892
Re: Flight control assemblies
Posted: Sat Dec 15, 2012 12:01 am
by 142YX
I also plan on using a #2 taper pin on my control sicks
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 2:43 am
by 142YX
Here is my idea for holding the control sticks straight while drilling the attachment. I used the same piece of MDF that i used to keep the horn assemblies parallel, additionally with a 3/16" think pice of scrap aluminum to make up for the difference in thickness
Here you can see the entire assembly clamped down to my (very clean, neat, and organized) work bench for easy drilling
This worked really well, the sticks came out pretty straight.
Also, i changed my mind from my above post. I just used #1 (AN386-1-8) taper pins for the control stick assemblies. I liked very much how the tail mixer came out which made me go in this direction, and i am convinced that a #1 is strong enough for this assembly (vice a #2). If i run into trouble with this in the future, I can always upsize to a #2 taper pin, or a -4 bolt. But i really like how they came out! There is absolutely zero slide to side slop in the stick attachment. The right stick only has the faintest amount of fore-aft slop, due to the stick tube being ever so slightly larger than the horn assembly… it is so small i may do nothing about it… but my gut tells me ill be doing something about that before to long. Had i used a bolt, i could tighten the crap out of it and likely eliminate the fore-aft slop… but then i think the whole assembly would be more prone to side-to-side slop developing over time.
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 11:18 am
by falvarez
Your setup looks great and the photos are quite helpful. I’m still a couple months away from installing my controls so I’m still a little unclear on the use of the taper pin…can you please help clarify? Is the pin used to help with clearance issues that would be present with a bolt? Or is it used to provide a more secure connection? Or something else?
Also, has anyone come up with a good way to make the passenger stick removable? If I can come up with a straight forward solution I would like to have the option of removing the stick as needed.
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 2:39 pm
by 142YX
I used the taper pin because in my opinion, getting a “good tight fit” with a bolt is a very hard thing to do on tube-over-tube connections. If you simply use a 1/4" drill bit to drill a hole for an AN4 bolt… you can be assured that it will wobble all over the place. AN4 bolts are all undersized, and vary +/- 1 or 2 thousandths of an inch… most of the time when i measure them they are .247 - .248". For any structural, single shear AN4 bolt in the fuselage, i have been using a .248" reamer as my final operation to get a “good tight fit”. But with the tube over tube assembly you have to cut two holes, one on each side of the tube. It has been my experience that if i am not doing this on a drill press… the “first side” hole tends to get larger than the “back side hole” during the drilling process. If the hole gets even 1 or 2 thousandths of an inch larger than it should be… there will be some slop/wobble which i do not want in the flight controls.
My description is pretty lousy… so here is a picture of what i am trying to say
Now if you use an AN4 bolt, you can tighten the crap out of it, deforming everything slightly, and introducing friction between the inner and outer tube which might be enough to prevent any feel of slop… but over time this assembly will have a greater potential to wear and get even more sloppy. I like the taper pin because you cant accidentally screw up the first hole, it is much easier to get a very tight fitting hole so that you do not have to rely on friction to eliminate slop.
Either way is probably fine, i have just convinced myself that this is better for me. Whatever way you choose to go, removing the passenger stick will only require removing the bolt/taper pin to get the stick off… but it might be a good idea to make a collar of some kind to slide over the now exposed horn assembly to prevent the bushings from backing out. The control stick being on there holds everything together.
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 3:20 pm
by falvarez
Great description and diagram…that makes it quite clear. Just one more thing for me to consider now
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 4:28 pm
by N111YX
The taper pins took out all of my slop in the sticks. I could not stand having the stick move 1/8th inch before it did anything. The Waiex uses one in the mixer because flutter would be catastrophic. Looks good, Nick!
Re: Flight control assemblies
Posted: Sun Dec 16, 2012 10:41 pm
by fastj22
I had the same issue as Kip. Too much slop.
I decided to just weld the pieces together since I have a MIG welder and know how to use it.
Re: Flight control assemblies
Posted: Mon Dec 17, 2012 2:14 am
by 142YX
Tonight i started to rig my pitch control. The plans (this is for the Waiex only) say to place a 1/16" shim in between the stick frame and the spar box, and with the tail mixer fully forward drill the required bushing hole for the idler-to-mixer rod. I misunderstood what the plans meant by the 1/16" shim and did this at first… it became obvious that it wouldn’t work because the idler-to-mixer rod was in the wrong spot at the mixer end.
I didn’t realize until this moment that the stick assembly goes over the spar when full forward. The instructions must have meant to put a 1/16" shim between the actual stick frame (and not like the forward most point of the stick like the above).
The problem that i ran into with this approach is that the entire assembly bottomed out at the idler before the stick frame was within 1/16" of the spar box. Because of this, i put a small shim in front of the idler and used this as my forward-most stick position for rigging. This made everything come out, from the best i can tell, correctly.
Now for the other problem i ran into. The ruder-vator push rods bottomed out by the spherical rod-ends hitting against their upper safety washer before the assembly moved all the way to the aft stop. Sorry about the bad photo… it was very hard to get a picture of this:
You can see here more clearly what is bottoming out. In this photo, i have two standard washers above the spherical bearing and it still bottomed out (the prints call for only one). It took THREE washers above the spherical to get all the way to the aft stop, and i find this to be somewhat ridiculous.
Waiex builders, did you have this problem? what did you do?
Re: Flight control assemblies
Posted: Mon Dec 17, 2012 3:35 am
by sonex892
142YX wrote:Now if you use an AN4 bolt, you can tighten the crap out of it, deforming everything slightly, and introducing friction between the inner and outer tube which might be enough to prevent any feel of slop…
Overtightening this bolt didnt work for me. It possibly just squashes and ovals the 3/4" tube making the situation worse. ie Bigger gap top and bottom between the tubes.
I understand that fore and aft slop may also still be a problem with one taper pin. I think the fore and aft play here could be eliminated by using 2 small taper pins one from the left and one from the right. Providing there is enough room of course :?:
