Closed-loop Control Systems

[Scruffmeister]

Hi All,

 

Per my previous post am building a Flair Magnatilla II. One of the things the instructions mention as an optional improvement is a 'closed loop control system'.

 

I'd like to do this, but does anyone have any tips on introducing this kind of system, or can you post some photos both of your control surfaces and of the servo bays so I can get some idea of what it entails?

 

Thanks

Arun

[Biggles' Elder Brother - Moderator]

Hi,

 

no photos to hand - sorry. But use Google image search and find plenty and it really is very straight forward to do.

 

Basically you can buy a closed loop pack of hardware consisting of clevis, some small bars with a hole drilled through near the end and threaded to screw into the clevis at the other end, sometimes a small locknut, some cable and some thin metal rings - which are actually crimps. You connect the clevis to the control horn, thread the bar in the back of the clevis so that its about half way in, thread the wire through the hole, draw it back 10-20mm or so then thread on the crimp. Place some epoxy inside the crimping ring and squeeze it tight with some pliers - this will hold the cable in place. Then you do the same at the servo end. You do not have to use a clevis at both ends if you don't want to - one end can be just a loop of wire and a crimp. But I tend to use a clevis at both ends as it gives me more adjustment possibilities. Make the cable so that there is just about no slack - but don't make it tight. To fine adjust just screw the bar into or out of the clevis. Stop the system from "unwinding" via the locknut. There are variations on this - but basically that's it.

 

Adjust the cables so that they are just taut - not tight. If you pluck them they should make a dull "twack" sound rather than a "ping" sound.

 

Personally I find closed loop systems easier to install than many of the alternatives such as snakes, pushrods etc. And it is a an excellent control system, easy to make very precise with no slop.

 

For a typical commercial closed loop hardware pack, of the type I mentioed above, see here

 

BEB

[Barrie Dav 2]

Remember not to run your aerial in the fuz alongside the closed loop wires.

[Doug Ireland]

When I fit them I use a small fishing swivel at the servo arm end. With this, the slack can be taken up in the wires without twisting them.