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*Pull Pull System On Profile*

Old 04-23-2005, 03:04 PM
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Zippi
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Default *Pull Pull System On Profile*

I just got the engine and all the gear hooked up on my Profile and I noticed something funny. The Pull Pull system will not center the control surfaces. for example, if I give it down elevator it goes back to center but when I give it up elevator it will not go back to the center. I worked on it far a while and gave up. It's also seems a little sluggesh when it moves. Any ideas ???
Old 04-23-2005, 05:20 PM
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DMcQuinn
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Default RE: *Pull Pull System On Profile*

Start with the servo. does it go back to the center every time? If so, then you have some slop in the pull-pull connection. The pull-pull cables should be slightly tight, but not like a guitar string. How many degrees different from up-center to down-center? If it is only a few degrees than I'd just fly it. In the air, the air loads will help to center the surface.
Old 04-23-2005, 05:26 PM
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Default RE: *Pull Pull System On Profile*

how tight do you have the cables?
Old 04-23-2005, 05:51 PM
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Default RE: *Pull Pull System On Profile*

The cables are not tight. Just tight enough to take out the slack. The ailerons are a direct connection 440 wire and they sometimes wont go all the way back. I'm using 50 % Expo on the elevator and rudder. This is a new flight pack from Servo City with HS-425BB and an HS-225 Mini on the throttle. No binding and the batteries are charged. I change the jumper on the receiver to Positive shift for Airtronics and put the crystal in. Nothing else has been done. It's got me puzzled.
Old 04-24-2005, 08:56 AM
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blue ice
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Default RE: *Pull Pull System On Profile*

I tried and tried on my Sledge to get the surfaces to center and finally gave up. They say it is nature of the beast. I ended up going to carbon fibre rod and now it centers the elevator perfectly.
Old 04-24-2005, 10:21 AM
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Default RE: *Pull Pull System On Profile*

I got most of my problem solved. I charged the batteries all night and this morning it worked fine for about 5 min. and then it started acting sluggish and slow again. The new flight pack is no good. I put a new flight pack in and now its fast and ready to rock and roll. The elevator and rudder still don't center perfect but it's good enough to fly. Just have to add the tank and it's ready to get vertical
Old 04-24-2005, 11:45 AM
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Default RE: *Pull Pull System On Profile*

I have quit using pull pull on small profiles altogether now, The combination of an encased cable friction with the angle at which these cables come out of the fuse make it impossible to center perfect. add a low torque servo and it can be a real problem. I like to slap a 2-56 rod on the outside of the fuse and fasten it with Du bro Landing gear straps and the problem is gone.
Old 04-24-2005, 02:01 PM
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Default RE: *Pull Pull System On Profile*

I am not a big fan of pull-pull either on profiles. I have had nothing but problems overall. You have watch the pull cable becasue they do strech over time and can lead to flutter.
Old 04-25-2005, 07:33 AM
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Default RE: *Pull Pull System On Profile*

Thanks for the info guys. I didn't like the way that it operated so I striped all the Pull Pull system off the plane and put a tube down each side of the fuse and ran solid wire to the elevator and rudder. This works much better
Old 04-25-2005, 08:20 AM
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Default RE: *Pull Pull System On Profile*

Hey Zippi, what profile are you doing this on? The advice above is solid as it is rare to see pull-pull on profiles these days. You'll only see the pull -pull setup on giant scale full bodied rudder systems like what we do in the big Hybrid Edge. In this case we use a quality setup like Dubro. If installed correctly according to the instrusctions and proper geometry then the system is flawless. Afterall that's what every giant scaler does on the big planes.
Old 04-25-2005, 09:04 AM
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Default RE: *Pull Pull System On Profile*

ORIGINAL: AFSalmon

Hey Zippi, what profile are you doing this on? The advice above is solid as it is rare to see pull-pull on profiles these days. You'll only see the pull -pull setup on giant scale full bodied rudder systems like what we do in the big Hybrid Edge. In this case we use a quality setup like Dubro. If installed correctly according to the instrusctions and proper geometry then the system is flawless. Afterall that's what every giant scaler does on the big planes.
It has nothing to do with the setup. If you take a look at the TopCap for example, the servos are in the wing and the pull-pull cables run through the fuse and then to the control surface. The problem is the angle at which they enter and exit the fuse. And to add to that, we use cheap standard servos which are not meant for pull-pull setups as there is too much pressure from the tension.
On giant scale planes there is no angle and therefore this doesnt happen.
Old 04-25-2005, 10:04 AM
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Zippi
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Default RE: *Pull Pull System On Profile*

It's an older Morris Hobbies su-do-khoi that I stuck an OS .50SX on. This is my first Profile and I wanted to proctice with this until the new "BAD BOY" Profiles or shipped. I have a new Saito .82 waiting to go on the business end. Everythings ok now except the weather. [:@]
Old 04-30-2005, 01:13 PM
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Default RE: *Pull Pull System On Profile*

Pull-pull is certainly a pain in the *** to build, but I think it's worth it. I try to ensure as straight a cable run as possible to minimise drag. Here are pix of how I did it in a Sledge. Direct routing, no running through guides, works flawlessly.
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