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Crossed Pull Pull cables?

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Old 06-26-2003, 01:51 AM
  #1  
Paul Cataldo
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Default Crossed Pull Pull cables?

Is there any advantage to using a single servo for the rudder pull pull sytem, and crossing the cables?
Why would you ever consider crossing the cables?
Is there any difference in the amount of throw you would get from the control surface?
Wouldn't it be better to NOT cross the cables in a pull pull rudder set up?
Thanks.

Also, I asked before on another post, but so far I have had no luck finding some 4-40 threaded eye hooks.
One member gave me Sullivans website, but I did not see them listed anywhere.
Thanks for any help guys.
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Old 06-26-2003, 01:57 AM
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David_Moen
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Default Crossed Pull Pull cables?

Crossing the cables would probably make it easier to get a nice straight line between the servo and the control horn I'm guessing...
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Old 06-26-2003, 03:24 AM
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KJohn
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Default Crossed Pull Pull cables?

Here are a few guesses:

1) The servo could not easily be reversed so they crossed the cables.

2) There was interest in having more 'pull' when the rudder was 'off neutral'. This might be of interest on tail draggers where they need to pull a wheel with the rudder. Crossing the cables would probably give more 'off center' leverage.

3) It was more convenient to bring the cables together near the rear of the fuselage before actually expanding them again and exiting the fuselage.
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Old 06-26-2003, 03:26 AM
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RCLIVIN
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Default Crossed Pull Pull cables?

Crossing the cables makes for an easy exit @ the rear of the fusalage, that is the only reason for doing it. If you do this using swivel ball links on your servo arm, connect one side to the top of the arm & one to the bottom of the arm, this keeps the cables from rubbing each other.
Gil
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Old 06-26-2003, 01:23 PM
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CrashMeister
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Default Crossed Pull Pull cables?

Eyebolt: http://www2.towerhobbies.com/cgi-bin...?&I=LXFV32&P=0 Their price is ridiculous (for 1), but I thought they came 4 to a packet, not 1. May just be a typo on their website.

Only reason to cross cables is to make the exit easier. Make sure cables do not rub against each other.

Craig.
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Old 06-26-2003, 08:51 PM
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Paul Cataldo
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Default Crossed Pull Pull cables?

Thanks for all of your help fellas, and I do hope that Towers website has a typo. That is ridiculous for only one eye hook.
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Old 06-27-2003, 12:13 AM
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MHawker
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Default Crossed Pull Pull cables?

If I remember right, I got my eyehooks at the LHS. I believe they were a dubro pack.
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Old 06-27-2003, 10:08 PM
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Default eyebolts

The Sullivan 4-40 eyebolts( part#549) come four to a pack. Tower has them. I got three packs a couple of days ago. Had to ask, tho, could't find them in yhe book. Item no.SULQ3249 @ $2.19. Hope this helps.
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Old 06-28-2003, 01:46 AM
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Paul Cataldo
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Default Crossed Pull Pull cables?

Well guys,
I'm looking at my Rudder pull pull situation here, and it's going to be a tedious job to get it set up.
My dual elevator servos are making it tight, but there is room.

What is the trick to finding the exact exit holes in the fuse for the cables?
Should I go with crossed cables, or not?
Also, Do most of you just cut a slit in the ply or covering of the fuse for the exits, or is something used as an exit "material"?
Just want to think this through and get some tips, before I get started.
This is a very nice 1/4 scale DP Edge, and I want to do a nice job.

Thanks for anyone who can help.
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Old 06-28-2003, 01:57 AM
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RCLIVIN
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Default Crossed Pull Pull cables?

Paul:
What you need to do is use a straight edge & try to lay it out is see if you would benefit from crossed cables. A narrow fuse @ the tail & not crossing the cables you will have to cut longer exits, with crossed cables the exit slots won't have to be as long. & the answer is yes to cutting slots, goldberg has long & short plastic pushrod exits if you would like that but a properly set up pull pull system dosen't really need anything. When you cut your slots, cut a slit in the covering, cut the four corners & peel the covering back, cut your slot, fold the covering back into the slot & seal with trim iron. Hope this helps.

Gil

cut your covering like this
>--------------<
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Old 06-28-2003, 02:14 AM
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Paul Cataldo
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Default Crossed Pull Pull cables?

Gil,
Even though you made that little diagram, I'm not really clear on how you say to cut the covering.
I SEE your diagram, but I'm not understanding the advantage to cutting those little v's with a slit in between them!
If you could shed a little more light, I'd be thankful!
Sorry!
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Old 06-28-2003, 02:15 AM
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Default Crossed Pull Pull cables?

On my 42% Spacewalker, I wanted to mount the rudder servo on the side of the fuselage under the cockpit to improve access through the hatch in the bottom. I turned the pull-pull cables 90 degrees. The rudder horn is horizontal, and the servo arm is vertical.

I used pieces of 1/8" plastic tubing to guide the lines through the aft part of the fuselage. If you leave a couple inches of tube past the last place it's glued, the end of the tube will "float" on the line. That keeps the line from cutting the tube and the tube from wearing the line.

The inside of the tube is very smooth and the pressure is low, so there isn't much drag on the lines from the contact.

While I don't do 3D, I do use the rudder a lot for take-offs and crosswind landings. The system gets a pretty good workout, and it's been working fine for a long time.

Roger
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Old 06-28-2003, 02:22 AM
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RCLIVIN
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Default Crossed Pull Pull cables?

Paul:
Cut a slit in your covering, @ each end of the slit cut the >-< which will make the four corners of your slot, peel the covering back, cut your slot in the wood, then fold the covering back into the hole you cut & iron it down with a trim iron, Hope this helps

Gil
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Old 06-28-2003, 02:35 AM
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Paul Cataldo
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Default Crossed Pull Pull cables?

I got it now, Thanks again.
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