Pull-Pull rudder cable exit angle

  • JRI
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6 years 3 months ago - 6 years 3 months ago #15459 by JRI
As my Mig.3 progresses I now have an issue where the exit angle to the control horn (not yet fitted) of the pull-pull rudder wire is quite high. I am worried this will cause the wire to saw through the exit or even fray (picture shows a rod exitting the fus') ...
.Any opinions, Ideas?
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Last edit: 6 years 3 months ago by JRI.

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6 years 3 months ago - 6 years 3 months ago #15460 by Phil Ford
Replied by Phil Ford on topic Pull-Pull rudder cable exit angle
Assuming the image shows the true angle of the exiting wire. I would suggest that as the rudder horn moves fully that only a slightly bigger hole is required. Look down from top of fin. imagine a 4 inch horn, what likely angle would be created. Possibly no more than 15 degrees?

I had a similar problem when working out the angle of an exiting elevator control rod. See image I used a bit of rod and paper card to pencil what number degrees would be taken in full rates
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Last edit: 6 years 3 months ago by Phil Ford.

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6 years 3 months ago #15472 by kevinross
Replied by kevinross on topic Pull-Pull rudder cable exit angle
Suggest you plot the full scale geometry with pencil on the worktable - Even better clamp the rudder servo with its horn in place and make a dummy rudder horn and string up some wire. Then if you cross the pull pull wires a steeper fuselage entry exit angle will be produced. But you should be able to establish suitable servo and rudder arm dimensions to align the pull pull cables with the slots in the fuz

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6 years 3 months ago #15474 by AlanF
Replied by AlanF on topic Pull-Pull rudder cable exit angle
If there are guide tubes already fitted that are giving you the wrong angle then I would consider removing them. I've used snake inners to great effect in the past, set at the right angle and fixed with epoxy+micro balloons to give a sandable faired lead out. This, used with crossed pull pull's and a rudder servo set at the optimum height should get you close.

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6 years 3 months ago - 6 years 3 months ago #15475 by JRI
Replied by JRI on topic Pull-Pull rudder cable exit angle
Taking both Kevin's and Alan's suggestions; the model has six long guide tubes insided the fus, pull-pull elevator, rudder, and tailwheel. Each has an entry and exit angle which requires the guide tube to act as the angle-changer at both ends. I have ripped the lot out and am installing close-coupled servo's instead (less scale but hidden from above so not too worried. I am hoping that because the model was designated as 40cc that my 55cc 3W up front will balance out the servos, otherwise it might be a late night visit to the local church roof! Also I have an inboard tuned pipe which might well have cooked the spaghetti of plastic guide tubes.
Last edit: 6 years 3 months ago by JRI.

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6 years 3 months ago #15476 by JonTappin
Replied by JonTappin on topic Pull-Pull rudder cable exit angle
Is it worth doing a balance check before you go down that route, don't want to end up needing so much lead that you need to rip it all out again?

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