Any good alternative ideas for single servo aileron linkage?

If I have to I'll use the parkzone linear servo and bellcrank again, but hoping for something different.

For a profile build or even some fuselage ones where geometry works out, control horns and pushrods splayed out from a double arm on a central rotary servo can work. But my current targets have fuselages and ailerons starting about an inch out.

I considered trying to do a classic Dubro / Sig / etc style strip aileron linkage yet smaller but wasn't sure what to do for the joint between the bent aileron pieces and the pushrods - a mock up in paperclips made just a z bend through a wire curlique loop seem suspect.

Current half done idea is carving out the holes in a micro servo horn to resemble the slots of the parkzone linear to rotary bellcrank, and mount the servo upside down between the ends of the torque rods so the slotted horn can act on them directly. Once I got enough of a slot cut that I could feed a narrow strip of sandpaper through the conversion process got better. May work, but it's going to be fiddly with throw depending on servo mounting height, and I worry about a tall thin servo rocking side to side... may need some serious gussets/buttresses.

Also haven't yet found good tubing to pivot the rods in - carefully rolling paper tubing works (who knows how long). Perhaps the right size hard rubber wire insulation?

FDM type 3d printing is an option - I've resisted because I think "heavy and fragile" but some care to work with the line deposition directions might yield something usable. Have also thought about printed jigs that don't stay in the model but hold placement while foam and glue structures set up.

(FWIW I spent some time searching past threads but wasn't readily finding much, probably there is already great information buried somewhere. Understandably lots of ultra micros are RET, but of those that have ailerons and a fuselage surely some use a different approach than parkzone?)

First thing I would do with micro is scrap the Dubro stuff. It weighs and costs, being unnecessary and impractical. Keep it light and keep it simple. I only occasionally use Dubro horns, as 0.015" sheet plastic with holes poked for the pushrods works fine, is basically free, and is light weight. I've used 0.047" torque rod wire at some length on 27"-28" models. Felt springy to the touch, but flew as well as anything else. For a smaller model like the Guillow's 16.5" FW190, I used 0.032" wire and no purchase parts for the pivots, using holes in the wing ribs for pivot points. CA hardened holes in wood hold up fine. Stuff like tubing is heavy and overkill, other than maybe in short length for bushing points. Bellcranks work but need to be slop free, with perfectly sized holes. The weight of the Parkzone hardware defeats the purpose. I used a bellcrank setup in a recent 14" EDF, with 0.015" pushrod wire. https://www.rcgroups.com/forums/show...pan-21-5mm-EDF

Originally Posted by AntiArf

First thing I would do with micro is scrap the Dubro stuff. It weighs and costs, being unnecessary and impractical.

I was referring to taking the idea, not the actual parts, even the 1/2 A stuff is comparatively huge...

For a smaller model like the Guillow's 16.5" FW190, I used 0.032" wire and no purchase parts for the pivots, using holes in the wing ribs for pivot points. CA hardened holes in wood hold up fine.

Of the sizes I have on hand .025 seemed good, just a hair thinner than the ones on the beat up electronics donor sukhoi wing floating around the bench.

I did the pivot in balsa when I used that as a material, but foam takes something else. Currently I have made paper sleeves to tape (maybe eventually glue) in a groove taking the role of the brass tube sleeve on the nitro era ones.

In your picture, what's the plastic part between the pushrod and the aileron torque rod end? That's the part I couldn't figure out how to minituarize, obviously the usual 2-56 nylon bits would be too big, and my paperclip mock up test of a z bend directly in a wire loop seemed suspect.

If I getting the question correctly, a cut portion of a servo control horn is thick CA glued to the torque rod. I bend the the torque rod end and insert it into one of the holes in the servo horn piece, before gluing. Sometimes I use a light CF horsehair wrap around it all, with CA. I use servo control horns for bellcranks also. The small washers were used to take up slop, where in more recent times I've gotten the S-bends more precise so that I don't need them. Not the greatest photo, but I also used the cutoff servo control horns for linkage points for internal rudder linkage arms. (2nd photo) https://www.rcgroups.com/forums/show...87&postcount=2

Another linkage point method is to place a number of nicks on the end of a wire with cutters, so that aluminum tubing will stay in place when glued over the wire. Flatten the tubing and make a hole for the pushrod. The second photo (Cessna CR2) uses the same flattened aluminum tubing end linkage. Worked well. https://www.rcgroups.com/forums/show...d-flight-video

For small models like Peanut WWII fighters I like to use small diameter heat shrink tubing to connect the servo pushrods to the aileron torque rods.


Tim

Originally Posted by Tim Cullip

For small models like Peanut WWII fighters I like to use small diameter heat shrink tubing to connect the servo pushrods to the aileron torque rods

That sounds like a clever idea leveraging the low force situation!

But I can't tell from the picture, do you cut the torque rods and have the tubing take a 90 degree bend off their top, or do you bend the torque rods very ends to point forward, or do you poke the rods through the wall of the heatshrink?

Having a way to make the throw adjustable would be great, but I really like the core of this idea!

I use a combination of the ideas already listed for torque tube ailerons. Crimped aluminum tubing with a .032 hole drilled for the pushrod from the servo. On the aileron end the wire is bent at 90* to enter the aileron. A section of WD40 spray tube is buried inside the aileron to accept the bent wire. On the outboard end of the aileron a piece of CF rod is glued in and fits into a CA hardened hole in the wing rib as the outboard hinge. The torque rod acts at the inboard hinge with the inboard side secured to the torque rod with small piece monokote trim.
Back to the servo connection. I use Z bends, make two rods long enough to overlap by an inch for each wing and heatshrink the two pieces together. This two piece method allows adjustment of the control syrface throw. I'll take some pictures here in a bit.

Originally Posted by UncleChris

That sounds like a clever idea leveraging the low force situation!

But I can't tell from the picture, do you cut the torque rods and have the tubing take a 90 degree bend off their top, or do you bend the torque rods very ends to point forward, or do you poke the rods through the wall of the heatshrink?

Having a way to make the throw adjustable would be great, but I really like the core of this idea!

The aileron torque rod bends 90 degrees at the bottom so it rises vertically up to where the servo pushrod is. The shrink tube connects the end of the servo pushrod to the vertical section of the aileron torque rod, the shrink tube is bent in the middle so half of it is around the servo pushrod and the other half is around the vertical section of the aileron torque rod. There is a very small gap between the end of the horizontal servo pushrod and the vertical torque rod, this is where the shrink tube has its approximately 90 degree bend. The bend in the shrink tube creates the "hinge" that allows the angle between the pushrod and the torque rod to change as the servo moves the ailerons.

Tim

Hmm, I like the simplicity but less so the lack of adjustability... currently I'm doing a second build of a plane where the ailerons on the original had poor authority, so I don't really know what I need.

That said, shorter = more so one could start out low throw and up it experimentally.

Guess maybe I'm doing bolt on wings so I can get back in there.. Have some little 2mm nylon screw left over from an electronics project, don't have the tap but in soft materials a Dremel ground steel screw should work.

deleted

Originally Posted by 56S

Crimped aluminum tubing with a .032 hole drilled for the pushrod from the servo.

Just back from the K&S rack at the neighbourhood hardware store and really liking this.

By crimping a bit of 3/32 aluminum tubing over the torque rid end I get a flag to drill a hole in, basically replicating that screw on nylon bit of the full size RC strip aileron setup.

The crump is holding well enough zi might do a test hop but I may try to get some hot glue in there for adjustability or CA for permanence. If I knew exactly what geometry I wanted I might use brass and solder it, maybe making it from thinner sheet, it's so small, I can barely weigh the aluminum and it's thick .014 wall (thought about beer can, too)

I don't think it's quite what you were describing with your two rods joined by heatshrink, but decided to try an L-bend and a parallel keeper rather than a Z, which should be easier to unhook without stress and more resistant to popping out or twisting the flag on the aileron torque rod end.

Looks like my 0.8mm heat shrink may work for the torque rod bearing sleeves in the foam, too.
Ironically for the keeper I think I may switch to thread wrap and CA.

Though I guess if I put the L bend in the add-on piece and made the one running to the servo the keeper, then that would give some "flap" adjustability. Maybe that's what you meant.

Anyway, I'm liking this, thanks for the idea!

Hmm, for conventional ends, what about a wire L bend doubling the CF pushrod and have that continue past the horn hole as the keeper?

(Replaced picture with a cropped version that will hopefully survive quality reduction)

I've now slightly modified the "two L bends joined by heatshrink" idea by giving each L bend piece a very slight bend outward and back to parallel to fit the thickness of whatever it's hooking into. Since that step is parallel to the bearing surface of the L it won't rotate out of position the way putting the step in the keeper would. I'm using .020 (.5 mm) wire that fits my 2g micro servo holes without enlargement.

Originally Posted by UncleChris

Hmm, I like the simplicity but less so the lack of adjustability... currently I'm doing a second build of a plane where the ailerons on the original had poor authority, so I don't really know what I need.

That said, shorter = more so one could start out low throw and up it experimentally.

Guess maybe I'm doing bolt on wings so I can get back in there.. Have some little 2mm nylon screw left over from an electronics project, don't have the tap but in soft materials a Dremel ground steel screw should work.

One thought about adjustability is that it weighs. Micro EZ links cost, and weight too. Z-bends look unsighty, although they only add a bit of wire weight and can't come loose like a Micro EZ link. For some time now I only use adjustment where absolutely necessary, and place precision bends on my pushrod ends. The one thing you want to get right is the centering, as a modern radio can make all the other changes for you. For torque rod ailerons I would prefer Z-bends over EZ links as they're lighter and can't come loose. With Z-bend adjustment, you can remove the aileron servo horn and place the pushrods in the next further out hole on either side, if you want more travel, and then readjust the Z-bends. I've rarely had an aileron authority problem however and I don't care for large aileron gaps, and set up the linkage for close to 100% transmitter travel when I create it, then adjust from there. From models ranging from 20" to 40"+ span, I've never needed more than 10mm aileron travel in either direction, usually a good bit less, and use next to nothing for general flying. If there's an aileron authority problem, it's probably something like my Citabria with an adverse aileron issue, which requires either significant differential and/or rudder mix (I have a light rudder mix). Larger ailerons can actually worsen control authority.

On throws in general, after a few builds of various size ranges, you know the offset distances OTOH. For 24"28" models where I use 5320/5330 individual aileron servos, I place a new hole in the servo horns for smaller gauge 0.020" or 0.025" wire between the second and third hole, and the aileron horn hole is approximately 7mm offset from the aileron bottom surface. With 1/16" aileron gap, 100% travel is usually just a bit over full aileron travel and is adjusted on the transmitter. As a general rule making both the torque rod arm lengths and servo horn linkage point radius arm lengths longer will reduce freeplay, due to any freeplay at the linkage points. Same scenario with tail feathers where the control horn linkage point and servo arm linkage point are both lengthened equal amounts. Too short is a problem, while I also don't care for long arms protruding off of my model, so I make my own holes for pushrods with no slop, and shorten the arm lengths as much as possible.

Originally Posted by UncleChris

Just back from the K&S rack at the neighbourhood hardware store and really liking this.

By crimping a bit of 3/32 aluminum tubing over the torque rid end I get a flag to drill a hole in, basically replicating that screw on nylon bit of the full size RC strip aileron setup.

The crump is holding well enough zi might do a test hop but I may try to get some hot glue in there for adjustability or CA for permanence. If I knew exactly what geometry I wanted I might use brass and solder it, maybe making it from thinner sheet, it's so small, I can barely weigh the aluminum and it's thick .014 wall (thought about beer can, too)

I don't think it's quite what you were describing with your two rods joined by heatshrink, but decided to try an L-bend and a parallel keeper rather than a Z, which should be easier to unhook without stress and more resistant to popping out or twisting the flag on the aileron torque rod end.

Looks like my 0.8mm heat shrink may work for the torque rod bearing sleeves in the foam, too.
Ironically for the keeper I think I may switch to thread wrap and CA.

Though I guess if I put the L bend in the add-on piece and made the one running to the servo the keeper, then that would give some "flap" adjustability. Maybe that's what you meant.

Anyway, I'm liking this, thanks for the idea!

Hmm, for conventional ends, what about a wire L bend doubling the CF pushrod and have that continue past the horn hole as the keeper?

(Replaced picture with a cropped version that will hopefully survive quality reduction)

I've now slightly modified the "two L bends joined by heatshrink" idea by giving each L bend piece a very slight bend outward and back to parallel to fit the thickness of whatever it's hooking into. Since that step is parallel to the bearing surface of the L it won't rotate out of position the way putting the step in the keeper would. I'm using .020 (.5 mm) wire that fits my 2g micro servo holes without enlargement.

I like that idea of the keeper being the rod connecting to the servo. I've done the L bend and keeper like that just never thought of the keeper rod going to the servo. Good idea!!
As far as crimping the tubing I cheated and use a nicropress crimper tool but anything will work especially if some glue is added.
I'd take some pictures but it would require pulling a wing off and currently packing for a week away. It looks like you've one upped my idea anyway.
Where it gets fun is the geometry of the linking to help with adverse yaw. My Tcraft has about twice the up travel than it does down. Make a big difference.

Originally Posted by AntiArf

Z-bends look unsighty, although they only add a bit of wire weight and can't come loose like a Micro EZ link.

Not using micro ezlinks or even aware they existed but I've had issues with ultra thin horns cut from retail bubble pack plastic popping over the Z and up the pushrod. On the most recent set I tied a knot of carpet thread around the inboard end of the Z and CA'd it to make a stopper ridge.

The one thing you want to get right is the centering, as a modern radio can make all the other changes for you

Should be able to adjust the centering, too. But as with all electronic adjustment it means leaving range / torque / resolution on the table.

With Z-bend adjustment, you can remove the aileron servo horn and place the pushrods in the next further out hole on either side, if you want more travel, and then readjust the Z-bends

Good point! I'd been so used to the lack of this on the linear servos I forget that in using a rotary I'm getting it back.

I've rarely had an aileron authority problem however and I don't care for large aileron gaps, and set up the linkage for close to 100% transmitter travel when I create it, then adjust from there. From models ranging from 20" to 40"+ span, I've never needed more than 10mm aileron travel in either direction, usually a good bit less, and use next to nothing for general flying. If there's an aileron authority problem, it's probably something like my Citabria with an adverse aileron issue, which requires either significant differential and/or rudder mix (I have a light rudder mix). Larger ailerons can actually worsen control authority.

Alas my current build is necessitated by an aileron authority problem. My 120% foam version of the Chris 3D Micro Pitts is a wonderful aircraft to fly and can be steered bank and yank, but as reported for pretty much every build in the plan's thread it just won't aileron roll, which is kind of counter to the idea of a Pitts. I blame the small ailerons and undecambered single surface wing (no inverted flight either). Given the existing one turns fine with the rudder I made a new lower wing and increased the dihedral from the minimum I had, converting it to a well behaved and tons of fun three channel plane I'm letting family fly as a step up from the HZ Champ.

Meanwhile I'm building a new one with plank wings and big ailerons in hopes of getting something actually aerobatic. Though I'm leaning towards installing custom electronics rather than a Sukhoi brick as that offers the possibility of expo and other software customizations which I don't have with my base-model Spektrum TX's - the insane roll rate (on the PZ Sukhoi could really benefit from some expo to tame it for maneuvering vs stunting.

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