Tim Flyer Posted February 23, 2020 Share Posted February 23, 2020 The rear has a virtual pivot point 10mm back from actual pivot point . This means to offset that a.virtual pivot point at the front needs to move forward not rearward. The current set it will mean that the wire being released will be released at a slower rate than the wire being pulled. The curved servo arms as in photo can offset this. If the curve is too much or arm too long it just means released line goes very slack so no problem 😊. Sorry but have to do bedtime duties now! Good luck John Edited By Tim Flyer on 23/02/2020 20:53:50 Edited By Tim Flyer on 23/02/2020 20:57:15 Edited By Tim Flyer on 23/02/2020 20:57:35 Quote Link to comment Share on other sites More sharing options...
Don Fry Posted February 23, 2020 Share Posted February 23, 2020 Is it the pink arm, or the black one we are talking about, and is the back end, pink black backend, or black pink backend. No double innuendoes please. off to bed. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 23, 2020 Share Posted February 23, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted February 23, 2020 Share Posted February 23, 2020 John. At what point are the wires at their tightest? A straight servo arm as you have, with a rearward set control horn, should in theory result in the wires being tightest when the rudder is centred and slacken off as it is moved to either side. This is an acceptable arrangement because during flight, the airflow pushes the rudder towards the central position, thus keeping the "pulling" wire tight. This arrangement also allows for the model to be stored with the rudder offset, giving slightly slack wires which will not stretch as the wires heat up and cool down. "Perfect" geometry, where the wire is at the same tension throughout it's movement will inevitably result in stretching during storage - unless it is slackened during storage. You say that the rudder centres with a right clatter. Does this happen when you move the transmitter stick slowly or just when you let go of the stick from full throw? Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 23, 2020 Author Share Posted February 23, 2020 It's just wrong Gary, never come across one like it, move the stick and it goes back with a clatter that shakes the rear end, I get air pressure would work on the rudder surface, but this isn't right, nothing i can find binding, and as i said, remove from servo, work by hand it's fine (tension there) . Set up wires, are right at neutral, work the servo, it all goes to pot. Just trying the curved horns. Quote Link to comment Share on other sites More sharing options...
cymaz Posted February 23, 2020 Share Posted February 23, 2020 Does this help?. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted February 23, 2020 Share Posted February 23, 2020 Are the wires at their tightest when the rudder is centred, and gradually slacken as it is moved off centre? Edited By Gary Manuel on 23/02/2020 22:25:21 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 23, 2020 Author Share Posted February 23, 2020 I may end up that route Cymas, I've a set of those rudder doodahs. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 23, 2020 Author Share Posted February 23, 2020 Well I've eventually found the problem, the curved horn highlighted it, the returning wire was dropping and getting stopped on the ply lip on the servo tray, (you can see it on first picture) turning the servo round should hopefully cure it, with the lip dremeled off. What a plonker. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 24, 2020 Share Posted February 24, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 24, 2020 Author Share Posted February 24, 2020 It is set up badly, we agree. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 24, 2020 Share Posted February 24, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted February 24, 2020 Share Posted February 24, 2020 Posted by Jason Channing on 24/02/2020 10:18:15: We might agree that, its the people who thinks its ok and rely on airflow. Might be wrong in an ideal world, but it has worked just fine that way for many people for decades. Right back to the first Panics and the like with daft amounts of surface deflection, it just works All it needs is to take up any slack around neutral. 10mm offset on the horns however is just plain wrong! Quote Link to comment Share on other sites More sharing options...
Nigel R Posted February 24, 2020 Share Posted February 24, 2020 john, you have a happy ending to the tale, no matter what the exact cause the problem is found, and that is a win Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted February 24, 2020 Share Posted February 24, 2020 Posted by Jason Channing on 24/02/2020 06:19:36: If the geometry is correct the wires should never be slack . if you are relying on the airflow to push the rudder back then its set up badly. .... and if you want to achieve this without changing the rudder control horns, then you may need an offset servo horn - with the offset towards the rear of the model (the opposite way to the black one in your latest picture). One thing to note is that having crossed close loop wires as you have effectively adds a small amount of offset when compared to uncrossed wires. PS. I do agree with Jason. I said it is "acceptable" for the wires to be slack when offset. I also went on to say that it is "perfect" when tight throughout the movement but can lead to stretching whilst in storage. What I didn't say is that I personally strive for the perfect setting, sometimes even making my own servo arms using 1.6mm epoxy glass sheet. This allows you to get the offset exactly right. The "Unacceptable" way would be if the wires tightened as the rudder was moved off centre i.e. too much offset. Edited By Gary Manuel on 24/02/2020 11:14:25 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 24, 2020 Author Share Posted February 24, 2020 I got rid of the clatter Nigel, am now pondering cutting the horns out, I've a pair with more forward rake that'll get me over the hinge line. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted February 24, 2020 Share Posted February 24, 2020 Slightly set back rudder horn gives a reduction in tension in the system when the rudder is fully deflected. Is there a problem with slack in the system that needs fixing? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 24, 2020 Share Posted February 24, 2020 Provide both lines are tight around the center then it should be ok . And its when rudder/ elevator is around the neutral position that flutter will cause a problem if lines are slack. When inputting control movements the pulling line will / should but enough tension to stop any flutter Unless you get the geometry absolutely accurate then the line pulling will always be tighter. Make sure that the width of the horns and the servo arm are the same diameter and that holes are the same distance from the center-line and it should work out Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted February 24, 2020 Share Posted February 24, 2020 Sounds a good plan👍 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 24, 2020 Author Share Posted February 24, 2020 Well I got there eventually, curved horn facing the rear, ran them uncrossed after a bit of tweaking with a file, no points for the individual who designed that kerfuffle, ball links under the servo arm because the bolt head hit the canopy floor, can't beat a servo at rear and a push rod. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted February 25, 2020 Share Posted February 25, 2020 That looks better. One observation though. Any reason why the ball links are underneath the servo arm rather than on top. On top would give more clearance underneath. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 25, 2020 Author Share Posted February 25, 2020 Yep, I say why in my comments Gary, they foul the underneath of the canopy when on top, they also run the cables better for the exit, poorly designed. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted February 25, 2020 Share Posted February 25, 2020 Posted by john stones 1 on 25/02/2020 13:36:11: poorly designed. Looks that way if they've not left space for the rudder controls above the servo tray. I'm surprised as I thought Pilot were a top brand. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 25, 2020 Author Share Posted February 25, 2020 Model is excellent, the closed loop thinking apart. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 25, 2020 Share Posted February 25, 2020 Maybe designed with clevises in mind? Quote Link to comment Share on other sites More sharing options...
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