linear servos
 

I find my self needing some linear servos. The conversion type are too fat ( 20.mm) I'm looking for something in the 10 to 12 mm range. So just how out of luck am I?
I need to move some tip ailerons with the servos mounted in the mid panel and I don't think I'll be able to keep the servo horns under the wing skin and there ain't no way they can fit in the fuselage, gods the linkages would be a nightmare..

RE: linear servos
 

Have you checked these out yet? I hear they work very well on the Genie
http://www.irfmachineworks.com/rds

Soar Dude

RE: linear servos
 

Thanks Soar_dude,
But the servo is about 15" with a 8 deg dihedral break in it from the control surface. I want to use Sullivan .032 cable to complete the linkage. If worst comes to worst I'll let the servo arm protrude the wing skin a bit and do something pretty so it does not look like an eyesore or a drag problem.

RE: linear servos
 

From the silence I hear I take it I'm screwed.

RE: linear servos
 

8 degrees of dihedral? Why are you putting ailerons on a high dihedral wing?

RE: linear servos
 

It's at a break. The middle panel is carrying most the dihedral. The effective dihedral of the wing is more like 4.5 deg.

RE: linear servos
 

Do you have dimensions? A plan drawing to scale?

RE: linear servos
 

This is kind of a cheap drawing. You are looking at the leading edge straight on, but it should convey the over all situation.

RE: linear servos
 

How about a top/plan view. You went to a negative angle on the tips? Thermal use? Slope?

You can use small diameter tubing and small wire wound guitar strings as the "wire". The wire wound guitar strings will flex around the tightest bends you can make in the tubing. As guitar strings come in many sizes you can find one that is a dead on fit for the inside of the tubing. Solder the ends to stiffen.

I've used this is a very small scale like sloper that a friend wanted built where the wings were just not thick enough for even the thinest servos. Put the servo in the fuse between the plug in wings. Left the whole thing assembled as the linkage was a PITA to connect. Could do the same but put the servo closer to the root of the wing where it will fit.

RE: linear servos
 

I hear what your saying. My big problem is it tips are removable. So any way you look at it there is going to be PITA connection some where I prefer it to be electrical. The plane is a thermal plane. The dihedral is set up between a aileron wing and a rudder only poly ship.(around 4.14 degs) I'm looking to use the ailerons for thermaling primarily. As I can't for the life of me figure out how to add flaps without killing the wing I intend to use spoilers. I know I'm still looking at 4 servos but the the integrity of the wing is much easier to maintain. What I've got going know is the inner panel is at o deg. The mid panel is at 6 degs. and the outer panel is at 3 degs. All degs. are measured from the zero line.

RE: linear servos
 

Since you can't find a thin servo to put in the wing tip you are looking at a mechanical linkage of some sort. Either a snaked cable or a bell crank in the main wing with the link to the aileron control horn out the bottom or top. At thermal speeds there is little if any drag in the wire and clevice connection.

I don't think you will find any advantage to the ailerons for thermaling with a polyhedral wing. Defeats the purpose of the polyhedral. Might as well use tip spoilers as any ailerons must have extreme differential to keep from imposing adverse yaw.

RE: linear servos
 

Here is what you can do with the RDS system.

Soar Dude

RE: linear servos
 

Soar dude,
The wing at that position is about 7 mm thick. Plus that break the actuating rod goes through is 6 degs negative so that the outer panel is 0 degs. I don't think the geometry will work. Here is the current game plan.

RE: linear servos
 

Use a ball and socket link. Much easier to connect.