Mike Smith Posted August 13, 2014 Share Posted August 13, 2014 Anyone who's been following my build blog will know that I'm currently building a scaled down version of the Ms Jax. The original design called for an internal control horn for the elevator, connected to a wire joiner. This sits right at the back end of the fuselage, up against the stern post. Clearly the stern post restricts movement so I have soldered up a joiner with a brass control horn set at a slight forward angle, so as to allow a small amount of backward control movement. However, movement is still limited and moreover, because of the angle offset, the response is non-linear (more up elevator than down). I can't envisage any way round this short of reverting to a more conventional external linkage, but just wondered if anyone else had come up with a neat solution for what I am trying to achieve? Mike Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 13, 2014 Share Posted August 13, 2014 You can compensate for the asymmetry by offsetting the servo arm to avoid losing resolution with ATV settings - makes a change from sorting throttle arm geometry for my clubmates... I had a similar problem with my Miles Atwood Special which I solved with an arced arm silver soldered to the joiner and a removable panel for access. Edited By Martin Harris on 13/08/2014 21:02:11 Quote Link to comment Share on other sites More sharing options...
Mike Smith Posted August 13, 2014 Author Share Posted August 13, 2014 Thanks Martin... looks like a neat solution Quote Link to comment Share on other sites More sharing options...
Mike Smith Posted August 28, 2014 Author Share Posted August 28, 2014 Ok, so I'm half way though covering my model and the solder joint has just failed on my internal control horn/elevator link!!! It's obviously embedded right at the stern of the plane where there is absolutely no access... I'm guessing my only option now is to switch to an external horn and run a Bowden cable to it, but just wondering if anyone has any other (constructive) suggestions?? Quote Link to comment Share on other sites More sharing options...
cymaz Posted August 28, 2014 Share Posted August 28, 2014 If you have used hairy hinges, cut those so the elevators are free. undo the servo end and pull the bowden cable out. I assume the cable is in a tube. Make a hatch on the underside of the fus so you can reconnect the clevis. That's the best I can come up with. I hope I don't have the same problem Quote Link to comment Share on other sites More sharing options...
Paul Sparks Posted August 28, 2014 Share Posted August 28, 2014 Hi Mike I would suggest some caution with using this type of concealed control horn, assuming that you will be soldering the brass horn. I did exactly this on my Chorus Gull (RCME PLAN) and even though I took extra time and care to clean all the parts before soldering and did a really hefty pull/push wiggle test afterwards the joint failed on the maiden flight ! Needless to say there was extensive damage to the plane on meeting terr firma. The plane is being repaired but I had to cut into the lower fuse to gain access to the arm and discovered that the solder had let go. I will be changing the control to an external type even though it looks less scale. Good luck with your build! . Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 28, 2014 Share Posted August 28, 2014 Horns like that MUST be silver soldered. To prevent the diffferential movement can be solved. The secret is that the pushrod,/ snake must be connected that right angles to the horn. Quote Link to comment Share on other sites More sharing options...
Mike Smith Posted August 28, 2014 Author Share Posted August 28, 2014 Thanks gents, looks like I'll have to put this one down to experience - at least it wasn't an in flight failure. There is absolutely no way of accessing the failed joint (not to effect a repair at least) as the fuselage at this point is no more than 1/4" wide. I have however managed to do a bit of keyhole surgery, drilling a small hole through the fuselage just behind the linkage and "grinding" away enough of the brass horn to release and extract, complete with attached pushrod. The linkage itself is still in situ so my intention is to now fit an external horn on one of the elevators and hopefully run a new pushrod to it. Peter... I'm not familiar with silver soldering... I guess it is a stronger joint than standard "electrical" solder. Does this require the use of a blowtorch or can it be done with a powerful iron? Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 28, 2014 Share Posted August 28, 2014 Yes, Silver soldering is a gas torch job. A good butane gas torch will work, You need silver solder, preferably one of the lower melting point ones. It is the next thing to brazing. Quote Link to comment Share on other sites More sharing options...
cymaz Posted August 28, 2014 Share Posted August 28, 2014 This may explain silver soldering Quote Link to comment Share on other sites More sharing options...
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