Servorahmen IDS servo mounts etc - step by step install?

[Doc James Hammond]

Hi Guys,
I'm fitting out an Aresti 2M aerobatics plane right now, and I'm using the Aloft supplied Servorahmen type servo IDS system with 2 x try out "mystery" (read "Chinese") wing servos and 2 x KST wing type.

Problem I quickly found is there does not seem to be any full instructions for actually installing the system in a 4 servo wing, and since its quite different from the normal way, I wondered if anybody would be interested in a step by step with pics?

Background:

I made these wings originally for "normal" type mountings using my own servo trays, but later decided that I really have to try the Aloft system, so this will be a REAL conversion from an off the shelf plane with pre-installed control horns to an IDS type.

If you are interested please post here and if there is enough I'll do the pics and write up.

Cheers,

Doc J,

Who remains, second cousin to the thunderclouds, lighter of dark corners, and all around good egg.

 

[Konrad]

Yes, please!
It will be this kind of content that will make this forum the go to forum for real information!
https://alofthobbies.com/ids-servo-tray-for-kst-integrated-drive-system.html

Seeing how long it took me to figure out the nuances of this tray, anything you can provide to lift the veils of ignorance would be much appreciated.
https://alofthobbies.com/external-bushing-servo-tray-for-kst.html

All the best,
Konrad

 

[Wayne]

I don't have photos of a full install, but here are some pictures that show the basics:

Detail of the bottom:

Using an existing control horn:

Using the internal "spoon":

Pay attention to the geometry of the spoon, the taller side goes away from the aileron/flap hinge. In this picture, the hinge would be on the bottom.

You can get a lot of throw that is very controlled when using the spoon. Best of all, the linkage can be contained within the wing, no extra drag. I honestly find these a little easier to install. The servo tray is about the same as a normal tray. The spoon just needs some material removed from the inside of the flight surface, then it all glues in.

The servo arms on these are one of the other neat tricks on these, they supply different lengths to get the amount of movement needed. You will probably be good with one of the very short arms if you are using the spoon. The cool thing about the arm design is you can use the full forward rotation of the servo without any worry of the linkage hitting the servo arm. No more crazy bent linkages and ground down clevises to clear the wing skins, etc. Yay!!

 

[Konrad]

I'm I correct that a lot of the success with these is dependent on tight gears and hinges? It looks like with the short leverage arms any slop will be exasperated leading to flutter..

 

[Doc James Hammond]

Great start from Konrad!

Couple of points there - before assembling the servos into the trays its a good idea to rough up the underneath tray surfaces ready for gluing into the wings. Also you need to choose which servo arms you want. I used the middle sized ones for the ailerons and the second largest for the flaps.

That done you can cut a bit of saran food wrap, or some tape to protect the servo under-surface to be glued inside the wing from accidentally bonding - I also use a bit of release agent wax since I have a lot around.

Dont forget to assemble in pairs - left and right sets, and also please remember that the servo arm needs to be further from the control horn (Spoon) position, and not in the closest position.

More coming with pics!

 

[Konrad]

Dont forget to assemble in pairs - left and right sets, and also please remember that the servo arm needs to be further from the control horn (Spoon) position, and not in the closest position.

More coming with pics!

Does this mean that the push rod needs to pass by the unused bearing journal in the mount to maintain some sort of geometry?

All the best,
Konrad

 

[Wayne]

[QUOTE="Konrad, post: 1492, member: 200"Am I correct that a lot of the success with these is dependent on tight gears and hinges? It looks like with the short leverage arms any slop will be exasperated leading to flutter..[/QUOTE]

That is the case for any aircraft. LOL

In my experience I get much better results with these IDS trays than I do with a normal linkage setup when using the same servos. I typically build with KST 135 or 125 servos, they have pretty good gear train in them. The MKS or the KST X10 series has a little better gearing.

I do some dry testing with the IDS linkages to make sure I'm getting the movement I need, just like a normal linkage setup, there is some testing to do before you mix up the glue. And yes, I sand all of the surfaces that will be taking glue prior to final installation.

 

[Wayne]

I found this drawing for spoon hinge alignment suggestions:

 

[Konrad]

Thanks for the drawing.
That explains it all. We are using short levers ( servo and surface). As the manufacture can control the clearance between the push rod and the levers (Spoon and servo arm) the real issue is with servo gear and hinge back lash (slop).

And, yes good geometry is needed with all aircraft.

 

[Wayne]

Yes, these are really intended for composite airframes that have no real play in the hinge.

 

[Konrad]

Most of my moldies are small 1.5 to 2 meter ships. I have a few NIB 2.5 to 3.5 meter ships that might fit the bill.

Are there smaller frames to fit maybe something like this with its live hinge?
https://alofthobbies.com/first-2-meter.html

I've noticed that the smaller the airframe the more susceptible they are to the drag penalties!

 

[Wayne]

Yes, actually we have the new monoblocks in the shop, but not on the site yet. I think they would be a good fit.

 

[Konrad]

Looks like I'll need to make another trip up north ( twist my arm ).

 

[Doc James Hammond]

Hi Guys, Looks like we are getting quite a lot of info here which s really good.

OK for those who have not had the foresight to order their planes "IDS ready" here I go with my Servorahmen install in an Aresti that is as "standard" - with control horns already fitted. I guess that IS actually standard?

Anyway as mentioned, the first thing to do is to install the servos in the frames and then the (complete, tested, sanded) assembly into the wings:

Please be reminded again to protect the bottom and sides of the servo with tape/wax - or you may never get it out again...

Flap first - please note that the servo is parallel to the HINGE line - not the pocket.

Now the Aileron:

 

[Doc James Hammond]

OK now its time to get rid of the lovingly (in my case) pre-installed servo horns.

 

[Doc James Hammond]

CAREFULLY remove the epoxy around the horn with a diamond bit and a Dremel or similar. Its really easy to make a mistake here so do take care. Here is where you become a dentist.

Remove the remains of the control horn carefully, then open up the subspar in the control surface until there is enough room for the spoon to fit. In this case it was flaps so the spoons hinge axes need to be a couple of millimeters forward of the hinge line.

Now do the same with the ailerons, but this time remember that the spoon axes need to be only very slightly forward of the hinge lines..

 

[Doc James Hammond]

Now its a good idea to install the hinge pins into the first bearing of the spoons before epoxying in -

because if you don't you will need to be a microsurgeon to do it later.

 

[Doc James Hammond]

Nicely scuffed up and degreased.

 

[Konrad]

"Cutting through the sub spar" This gives me concern.

With your high speed ships have you noticed any structural concern with this? Is the wing more likely to go into flutter as the trailing edge appears to not be as rigid in flex (bending moment)? Or are the drag benefits worth the rigidity loss? Are most molded wing actually over built with the sub spar? Is the sub spar really just something to hang the control surface on?

 

[Doc James Hammond]

Hi Konrad - there is really absolutely no choice in this if spoons are used, but no, I have no concerns. the control surfaces are at least one layer of carbon top and bottom, and in any case gluing the spoons in the spar gap replaces all the spar that was lost with epoxy and filler - I don't use micro balloons for anything - ever - by the way.