Could someone explain to me the best way to set up a closed loop system for rudder and elevator. Some people say the wires should be crossed while others say it doesn't matter. Who is right and why? By the way, I will be having a servo on each elevator as the plane will be over 20kg. and will require a CAA exemption certificate. The less weight I can keep from the tail end the better. Also, can the wires deviate from dead straight ?
Thanks for any help.
Michael.
Try it both ways and see which you prefer. I recall a magazine article many years ago that advised you cross them.
I have a 25 year old Proctor Mini Antic. The elevator cables run down the outside of the fuselage from external bellcranks to the tail. A pair of cables on each side for each elevator half. Over the years I have run these cables both crossed and uncrossed. In this particular set up, when the controls are moved, a lot of slack occurs in one cable of each pair when the cables are not crossed. When they are crossed you still get some slack but no where near the same amount. I don't really think it matters but I tend to cross mine.
One advantage of crossing is you can keep the exit on the fuselage further to the rear. If that matters that is.
Michael-
If by 'closed loop' you mean a pull-pull sytem of flexible wires vs. a single rigid pushrod per control surface, there is a good article by Jerry Nelson (something of a master of the art) in the just-out June
2005 issue of "FLY RC" magazine about setting them up. Specific issues like crossing the wires are addressed with good graphics to illustrate why/why not that would be quite difficult to describe adequately without them.. Not sure if this magazine is readily available in the UK, but if so it's worth hunting down - the best currently available on this side of the pond, IMHO.Abel
refer to Alan's Hobby, Model & RC Web Links
regards Alan T. Alan's Hobby, Model & RC Web Links
I have used pull-pull system on many of my aircraft over the last few years and I have never crossed them and also never worried about the slack in one cable , but you can install in such a way as to eliminate the slack. To better understand why the slack occurs , do a Google search for "Ackerman principle". It's very well explained there.Also a search on pull-pull rudder will give you lots of information on installing a pull-pull system.
Ken Day
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