Closed loop compensator

[MMG]

Hi, I am aware of how a closed loop system operates for flying surfaces. I am about to start building a Flair Magnatilla and will incorporate closed loops for the rudder and elevator. However, in reading around the subject, mention has been made of a compensator as part of a closed loop system. Apart from a very poor sketch on a shop website (not Flairs) which gives no detail, I cannot find any other information .

Can anyone help please with an explanation or point me towards a site that reveals all?

Thank you.

[PatMc]

I use closed loop on the rudder & elevator of my Magnatilla. I don't know what a compensator would do or how it works. Mine has fulcrums between servo & surface to avoid a constant strain on the servo bearings. It also makes it easier to remove the tail as a unit if required without having any adjustable clevises on the rudder & elevator horns.

BTW the model has had substantial cosmetic mods, hence the non-standard turtle deck former.

[Seamus O'Leprosy]

MM I think they were made by radio active. basically it was a unit that went on top of the servo and had an inbuilt spring to compensate for one side of the closed being longer than the other resulting in uneven control geometry . The fact that you don't see them nowadays is you rarely need them.

You will be fine on the Mag just connecting them up with clevises at one end

[Peter Miller]

I remember a compensator many years ago. I seem to remember that they had a habit of falling to bits.

Just use the idler bellcranks that PatMc uses. Make sure that a line drawn between the two holes in the control horn passes through the centre of the hinge.

[Ernie]

Hi MMG, I think Flair made one a few years ago. It was a complex affair, which didn't seem to do a lot. You don't really need it...Add lightness and simplicate, and don't make the wires drum tight

Ernie ( I think i've got one somewhere in the depths of the workshop, if you feel a desperate need to have one)

[Doug Ireland]

I like PatMc's idea, i think i may modify some of my models while the weather is still too windy to fly.

[MMG]

Gentlemen,

Thank you for the responses to my query. They more or less confirm what I thought a compensator was all about; tension. I did spot one advertised on the Flair site but they gave no details other than you might consider buying their spares catalogue to find out more! The paucity of information `out there` seems to back up your views/advice concerning their use.

Thanks for the background you have passed on re closed loops, they have given me food for thought.

[PatMc]

Posted by Peter Miller on 14/03/2012 08:11:58:

Make sure that a line drawn between the two holes in the control horn passes through the centre of the hinge.

That's what I've done in the example shown but it's not the best way. It's best to arrange that when the servo is off normal the non-pull line slackens slightly. This can be done by arranging that either the servo or control horn holes are not at 180 degrees whilst the other end is. But it must be done in the correct sense or the lines will bind.

The advantage of this is that in the symetric way shown the line tension will always be pulling on the control surface hinges but with the correct assymetric set up by leaving the surfaces off normal when the model isn't in use the tension will be virtually nil.

I'll draw a sketch of the preferred method & post it when I have time.

BTW even as shown it's surprising slack the lines can be & still have less slop than most push rods & virtually all snakes.

Edited By PatMc on 14/03/2012 11:43:49