First time using a pull pull and got this question:

I've got the rudder end set up no problem. At the servo end, instructions say to "ensure the cable is the correct length". What with the "loop de loop" that the cable does going through the clevis holes and that little brass sleeve, how do you ensure that after the cable loop is tightened, the cable is in fact the correct length?

Would you attach the clevis to the horn then thread the cable etc etc?

Obviously my concern at this point is that I could measure the cable and loop it so the clevis reaches the horn but how do I ensure that after the loop is tightened that the cable is STILL the correct length?

Thanks.

Make sure your servo is at it's electrical center. Place the double servo arm on the servo and make sure it is at 90 degrees to the servo. I assume you are using the threaded adjusters (have a small hole at one end for the wire to pass thru, clevis threads on other end). Make sure the clevises are screwed the same amount so each adjuster/clevis is the same length(put a locking nut on to tighten against the clevis). Thread your wires coming from the rudder through their guides and pass one end of each through a brass sleeve and then the tiny hole in the adjuster. Attach the adjuster and clevis to the servo arm in the desired holes(i usually start second one in ). clamp your rudder so it is straight with the vert stab. Pull each cable taut, just take out the slack, and bend it where it passes thru the adjuster hole. Double the end back through the sleeve, and then loop it over and back through the sleeve again, pull the slack out of these loops and then crimp the sleeve. This locks the cables in place so they don't slip.

If everything is done right, the cables will be almost tight, and both the same length, and the servo is still centered and the rudder is still straight. Loosen the locking nuts and turn the adjusters equally until the pull-pull has no play, but is not stretched and bending the rudder arm from tension. Retighten the locking nuts, power up and test the action. If the rudder stays centered, you're good to go, if not, back off one wire and tighten the other the same amount, until the rudder centers.

Great. Thanks for confirming the clevis (with the pin hole ) is attached to the servo arm b4 pulling the cable tight.

Thanks.

Remember to thread the clevis on about half way at both ends of the cable before you tighten it. This will ensure that you have some adjustability after everything is tightened. Did you loop it around three times?

Haven't done the final clevis attachment yet (but I will). Thanks.

What plane are you doing the pull-pull setup on? Sometimes due to working space inside the plane, it might be easier to put the adjusters and clevises on the rudder arm--allows you to make adjustments outside the plane, and some low-and-slow scale models have them there for scale appearance (J-3 for instance)

Ryan STA-M. No room on the rudder. All is basically hidden inside. Lots of working room inside to do this. Thanks for the tip though.

One question I do have though: the tail servos are side by side (two elev, one rudder--rudder is the p-p). Because I don't have (and don't want to get) a servo reverser, I have to put one of the elev clevis' on the same side as the other (so they rotate in the same direction but operate opposite to each other). Because of that side switch, the control rod is right under and real close to the rudder arm.

What I want to do is put a 1/16" strip of balsa front and back of the rudder servo so it is lifted up by a 1/16" so the elev control arm will clear the rudder servo.

Is that a good idea to lift the servo up so that there is a bit of extra clearance? It would be a level front-and-back lift up, sort of like when you put a washer under the rear bolts of an engine to give it a bit of down thrust as needed, only this would be both front and back of the servo.

Hi!
You don't have to measure anything!
You just mount the wire on the side-rudder/elevator and then draw the wire inside to the servo/servos and there you mount the wire to the adjustable linkage.
see pictures.
Regards!
Jan K
Sweden

the linkage on current plane (least ways the one I have) is different than the one in your first pic. I'll post a pic later to show but basically there's a little brass tube that goes on the cable then the cable is threaded through the tiny hole in the clevis then looped back through the brass sleeve then back again thru the sleeve and pulled tight to make an ever closing loop between the sleeve and the clevis. When the distance is right, the sleeve is crushed flat.

In your pic it looks like the tube part of the clevis is crushed to hold the cable. Not in mine. I'll pic later. Can't pic as the cable that is already looped is attached to the rudder/rudder is taped to the fuse for finalization of the system.

If you're using a computer radio (and I assume you are with multi servo setups) you can program the Tx to reverse one of the elevator servos- you don't need a reverser. There is also a reversing "Y' adapter that will do the same thing, or you can make your own --just clip and reverse the power wires(black and red on Futaba) on one servo lead downstream of the Y. You don't need but a mm. of clearance between the servo arms , but I like all my servos "pointing" the same way.

I do have the puter radio but the elev servos are ganged on a Y so the radio reverser won't work (BOTH would be reversed which is not my intent ). I didn't want to spend the bucks on the reverser. Cheap so and so you know.

HOWEVER, I like the idea of clipping and reversing the wires. So simple and don't know why I didn't think of it. Thanks for that. I also won't have to worry about the clearance issue either, doing it that way.

[sm=thumbup.gif] to you sir (and also to the others that offered their help).

Hi!
The system I use is in reality what you describe; a short tube (crome plated brass) which I push the wire through...then the wire is pushed into a small hole drilled in the 2mm controll linkage onto where the clevis is screwed.
The wire then goes back into the short tube and then back again.
Then the short tubing is cramped at two places with a plier. You should never crush the short brass tubing as it loses some of its holding ability that way.
See picture of my PBY Catalina (Kyosho).
Regards!
Jan K
Sweden

Now I see what you were doing. The equip I have is similar to previous posts though. There is the usual clevis but there is a longer tube opposite the horn end that has two tiny holes for threading the cable through. Only the clevis comes in contact with the horn, not like yours where the cable does. Also with your way there is no "disconnecting" the cable from the horn without ruining the "tube-crush" component. Mine you just slide the keeper off and pop the arms open/slide it off the horn.

Hey voyager,

What pull pull system are you using (what manufacturer)? If you are using a Dubro set up like I did, then you may have a hard time getting the plastic coated cable through the crimp tube 3 times. If you find it dificult, then strip off just enough plastic coating off the cable to allow you to make it through the required 3 times. Don't short-change it and just settle for passing it through twice. If you have any questions, I can post some pics of how I set mine up on my H9 Aresti 40. Good luck to you.

Gary

SWB mfg makes a tensioning system that is pretty easy to install. Put the ball links, 4-40 threaded rod, and nylon tensioners onto the servo arm. Then tape the control surface at center, put the servo at center. Now just pull the cables through and crimp them. Make sure you take up all the slack but don't move the servo or surface. Also make sure the tensioner has at least 50% adjustment left to tighten it up to proper tension. I really like the SWB servo arm and tensioning system. I bought the pull pull cable from him too. Note that the servo arm is way longer than it needs to be. No biggie

It's the setup that comes with the GP Ryan. I'll post pics a bit later.