Scale aileron linkage.

[Skeet Wyman]

So I have what might seem a simple question to some but I need to know. Have been building flying model aircraft for over 50 years and always love scale aircraft as my 1st choice. Recently I started my 1st 1/4 scale ( I have built several full scale) aircraft a Ziroli Staggerwing. So naturaly I have been disecting as many facts as I can. But one reacuring thing I see and dont understand is why I see so many absolutly stunning aircraft with IMHO ugly non scale aileron linkage sticking out of the bottom of the wing. What am I missing? And I dont mean they accept that at scale judging because I wouldnt, but with the class of aircraft I have seen I know these masters have a reason I dont know, right? Is it to hard to control the torque spec required or what? For me problem solving IS the fun in building and I enjoy it as much as flying. So. Can someone please enlighten this poor soul?

Skeet

[Nick Somerville]

Hi Skeet, you are not wrong about the way pushrods sticking out of the underside of wings can really spoil a scale model. However 1/4 scale is big and the weight of both the surfaces and loads of ailerons and flaps can be considerable. For that reason alone the exterior pushrod setups are both easy to set up, easy to service and are very reliable.

Danny Fenton, who regularly posts here is a champion of the RDS (rotary drive system) and following his guidance I set up this for my 1/5.6 Bates Sea Fury ailerons (page 2).  It’s also worth noting that the majority of composite Thermal and slope race soarers use hidden linkages and certainly for the F3F type model, these need to be very powerful and slop free. Interestingly we don’t really see this type of precision technology being used much to hide control links in large scale warbird builds.

 

Back to the RDS system I employed, it wasn’t without its challenges. The hardest part is finding the necessary servo output parts to hold the torque rods. I had one failure of what I had done that fortunately didn’t cause a mishap and I have re fabricated the output discs to make that weak point more reliable. 
 

With so many variables in model design/proportions every subject requires individual decisions to be made. I suspect there is a hidden linkage solution for most, but the extra work and serviceability can mitigate us from exploring them. Just my opinion. BTW I was pleased to find that my current build Fw190 has an external aileron 

horn as scale. Though the flap links are hidden.

 

[Skeet Wyman]

Thats awesome (your bird to!) I had heard and seen of this system and that also was a wonder to me. If it exist why dont more use it? I get when it comes to scale some need to draw the line somewhere. But for me that line is a ways away from the scale control link on ailerons. I feel sometimes going full scale is best. Example: on my staggerwing I am using a scale tail gear arrangement (retractable) . Instead of Robart tail wheel (not scale at all) which needs a electronic device to slow to scale speed. I am using my own design running off the main gear drive (like the full scale) Its not for the faint of heart but very rewarding. I am also attempting stearable rear wheel by diferentail braking. My tail wheel has an adjustable lock (for centering before retracting) again scale. Havent got there yet but doing so IS THE FUN. hope this video is good eneough to see how it works.  Dont think this worked so here is the youtube link.  

 

 

1449382439_Staggergear.MOV

Edited January 17, 2023 by Skeet Wyman

[Frank Skilbeck]

On my mates 28% scale 190 he has fully enclosed the aileron  and flap linkages (but not the elevator), but the wing is very thick so it wasn't a too much of a problem. By positioning the connections on the surfaces and servo arm you can still have the torque, but the effect of any slack in the linkage will be amplified.

[Christopher Wolfe]

G'day Skeet.

 

I saved this picture in my 'might come in handy one day' folder.

 

 

Never actually tried it but it might be useful for your quest.

 

chris

[Martin Harris - Moderator]

This was my solution - a larger model with a standard servo but would probably scale down using smaller servos.

 

[Skeet Wyman]

Thanks for those replies I now have the confidence to go for it. I will be doing hidden arms on my staggerwing. I already have the rudder and stabilizer done, those where easy. I now will try one these ideas on the wings. Either way when I do I will share.

Cheers

 

[John Rickett 102]

Chris, The diagram of the flap/aileron mechanism is interesting, though confusing for me. Can you explain how it works - is the horn fixed or floating and why is the suggested gap shown to be much less for an aileron installation than for flaps, I would have expected the gap would be greater for an aileron installation, perhaps that's because I haven't grasped yet how it works!  

[Ron Gray]

Chris’s picture is of the Servorahem IDS, 

[Frank Skilbeck]

John, the sketch is a typical hinge on a moulded glider wing, basically the hinge is the wing skin (thinner at the hinge point), the aileron hinge is usually the top skin. But you can substitute conventional hinges on a scale model and use the same set up with a hidden horn, on the gliders it's done to reduce drag. 

Edited January 20, 2023 by Frank Skilbeck

[John Rickett 102]

Ok Chaps, thanks for that. Would be a bit awkward for us (conventional/dyed in the wool/old fashioned) balsa bashers by the looks.  

[kc]

John, I am glad I was not the only traditional balsa basher to not quite understand Chris's diagram!  

I am still not sure whether the horn is glued to the top surface and what  " fit the ledge exactly to the pocket size" really means.   But I am not going to build a moulded glider so it does not really matter ........... but it would be nice to know...........  

[Ron Gray]

14 minutes ago, kc said:

I am still not sure whether the horn is glued to the top surface and what  " fit the ledge exactly to the pocket size" really means. 

Yes, the horn is attached to the underside of the top skin and the ‘ledge’ is the node that sticks out at the bottom which is located against the bottom skin. 
 

Whilst the sketch is showing the system in place in a glider wing just think off it as an off-centre location for the push rod. Being off centre it will create a turning moment about the hinge pivot point and this principle can quite easily be used in ‘normal’ construction. I used  it for the rudder control on my YT Hurricane

 

[kc]

Thanks Ron.

I expected that the node (ledge) would be glued to the bottom skin, but perhaps there is some reason not to.

 

I think I prefer linkages on my planes to be visible and ensure any problems can be seen before it's too late!  

[Ron Gray]

Not a lot of node to stick!

 

I agree with you about checking linkages and I do check the rudder one at the same time as the others, the visible bit is ok but as it’s servo is hidden in the tail that end is not visually checked that often and I rely on the hand wiggle check!

[David Hazell 1]

Probably for me as much as anyone in future, the hyperflight page has some more details on how to use this solution. Looks brilliant I have to say!

 

https://www.hyperflight.co.uk/products.asp?code=SRIDSM-MKS6110&name=integrated-drive-system-mono-for-mks-hv6110

 

[Simon Chaddock]

Surely whether the control horn is visible or not depends on the original aircraft. Horns are very visible on a Tiger Moth as are the streamlined fairing for them on Concorde. 

This screen grab from a video perhaps shows why many RC plane builders tend not follow the scale control horns.

The aileron linkage for a MkV Spitfire.

Note the huge mechanical advantage difference between the cable runs and the aileron linkage to the horn. As the movement is then so small it requires all ball bearing pivots in metal brackets To make matters worse at a reduced scale the tolerance accuracy is even greater requiring a level of engineering likely beyond most RC builders.

Just saying. 

[kc]

Thanks for that link David - hyperflights pictures ( in English! ) make it easier to understand.   Beats the German website for the same items hands down - much better photos.  

I have to say I probably would trust that as much as an external visible system as it looks as though there is not too much that can come adrift.   Probably needs a hatch for the servo which could be used to inspect the works.  I liked the external bearing for the servo output although the whole thing  depends on whether the plastic tray lasts without fracturing or deteriorating.   I am impressed.

The one comment I would say against the idea is that with a normal external horn and quicklink with clevis that it if the ailerons get moved whilst stored or assembling model at field then the servo just gets wizzed around without much harm.  With this internal system the leverage is quite different and it seems to me that if grabbing an aileron then the servo would probably not turn and the result would be the internal horn would take the strain instead and probably come adrift.   Would need a lot more careful storage and handling - but if it's a special scale model etc one would be more careful than with an everyday model.

[Lima Hotel Foxtrot]

Would it be too simplistic to say "torque rods"?

Edited January 20, 2023 by Lima Hotel Foxtrot

[John Rickett 102]

David, thankyou for supplying the Hyperflight link, now I understand how the system works. 

[La 5 flier]

I have tried the RDS and I have built the Supermarine aileron links for the Taylor Spitfire. Your original post posed the question regarding why don't more scale modelers use a hidden, scale aileron link setup versus the ugly control horn to servo arm hanging out the bottom of the wing look.  In a word; leverage....or rather, the lack of it. Our models at 1/5 and 1/4 scale shrink the lever arm to something miniscule compared to the aerodynamic loads being imposed upon the control surfaces. Our models typically exceed the scale speeds so the loads are even more extreme. The other factor is flutter. The smaller the control arm moment, the more likely flutter will occur. The RDS solves these problems but it does require careful setup plus one must be able to solder stainless steel (unless the parts have been replaced with non-stainless.) Overcoming these issues and it works really well. Building anything duplicating the full size setup usually results in significant slop leading to lots of motion and flutter because of the aformentioned lack of leverage. The control horn/servo arm hanging beneath the wing extends moment-arms resulting in a significant increase in leverage and reduction to the potential for flutter.

[Simon Chaddock]

A scale model flying  plane is most likely only scale its visible features. Nothing hidden inside is ever likely to be scale so why a scale internal linkage?