I,m wanting to install a pull pull for my rudder and elavator on my 1/4 DVIII I have never installed a system like this any help would be appreciated.
Dave

I am sure if you search on "pull-pull" you will find lots of information. MinnFlyer has produced numerous drawings on the subject so you should be able to find some of them...

In short -- keep it square and it will all work out. Ensure the pivot points are the same, or offset the same, and keep the widths at both ends the same and it will work great!

Brian Felice has an awesome site with a great page on Pull Pull. Also check out his "Wedge" airplane which uses all Pull Pull. I've talked to him several times by email and he's super helpful. Also check out the Ackerman page which describes the Mechanical ways of the Pull Pull.

Jeff

[link=http://members.cox.net/bdfelice/Pull-pull/pull-pull.htm]Pull Pull[/link]

I purchased a Dubro pull pull pack and used the "wedge" site as a reference.

http://www2.towerhobbies.com/cgi-bin...?&I=LXD858&P=7

I setup the servo and control horn so that the lines ran parallel, and put the control horn (pair) just *slightly* back from the hinge line to introduce some "Ackerman effect" and it work out fine. At full rudder deflection the non-pulling side goes slightly slack as expected. At center, both lines are tight.

gidday fellas, I've just checked out Brian felice's site on this subject and it has raised a couple of questions for me. One is, why is it nessesary to have the Ackerman effect? I have installed a closed loop system for both my elevator and rudder and was carefull to make the system symmetrical. I have a bellcrank, operated by a short stiff wire pushrod to the servo and cables from bellcrank to the control surface. When the servo is not conected to the crank, the control surfaces just flap in the breeze with no binding or loosening of the pull wires. This also eliminates the constant tension on the servo because the bell crank takes the strain. This system works great without Ackerman.

Secondly, why on Brians system, no cable has a straight run to the control surfaces but cross and bend their way to the exits. I was led to believe that minimal binding was called for so no unnessesary strain was put on the servo. I understand that he uses teflon guides for the exits but surely it must bind some, especially his ailerons.

The non-straight cable runs also made me wonder.

The value of adding positive Ackerman, IMO, is simple to ensure you don't inadvertantly end up with negative.... which would be a bad thing.

If you're careful with the whole setup there is no reason I can see why you'd end up with negative. If your a bit sloppy (just a bit) I can see how the non-pulling wire could tighten up and cause problems.