Control horns, is it just me or... ?

[Clay Schmidt]

Keith,

I'm gathering pieces for my winter project and found the same problem as you have.  I did buy the horns from RC Enterprises and I'm glad I did albeit the cost was a little steep. ( Excellent service from those folks by the way.)

Anyway I'm going to use helicopter hardware for my control linkages and the ZN horns allow me to do that.  You will be able to position the horn exactly on the hinge line .  The pushrod mounting hole is tapped 2mm which is standard for most balls found on helicopters.  For the link I will use the Rocket City ball link.  These links are considered the Cadillac link in the heli community. For the pushrod I will use Quick UK 2mm stainless rods.

This set up will cost no more than the MK stuff when it is all said and done.  It is a heck of a lot easier ( and cheaper) to maintain, and you will be able to make adjustments by merely popping the link, give it a twist and pop it back on.  Another great benefit to this system is you can size the link to the ball for a no slop and friction free fit.

If you are interested I can point you to the sources for all this stuff.

Clay
  ----- Original Message ----- 
  From: Keith Black 
  To: discussion at nsrca.org 
  Sent: Tuesday, September 02, 2003 8:57 PM
  Subject: Control horns, is it just me or... ?


  When it comes to control horns for pattern planes it seems to me that some of the most commonly used choices have a major flaw.

  On my last plane I used the MK Aluminum Horns on all surfaces except for the rudder where I used the IM pull-pull horns. Both of these are nice horns except they have a major flaw when using a pull-pull setup. The flaw is that the little black plastic arm that screws onto the horn and connects to the clevis is so short that it doesn't extend out over the hinge line. I know that with pull-pull systems it isn't *absolutely* necessary for the connection to be exactly above the hinge, but the further back it is the more slack there will be in the cable that is not pulling.  In my opinion with these horns the connection point is too far away from the hinge unless the horn is virtually mounted on the control surface bevel (especially when it comes to rudder). This can easily be seen in these "instructions" for installing the MK horns http://www.centralhobbies.com/buildingtips/mkhorns/mkhornsinst.html. Notice that in this picture there surface isn't beveled yet and the horn is almost on the edge.

  On my new plane I wanted to avoid this problem so I did some searching to find a better solution. To begin with I looked for a longer arm to connect to the MK horn, one that would extend out to the hinge line. I found two options from Sullivan but both require too big of a horn thread (6-32 and 8-32). My search then led me to two other choices that seem to be good alternatives. The first is the ZNLine aluminum control horns, but these are apparently only distributed by ZNLine (http://www.znline.com/produits.php?langue=english&cle_menus=1025879382&cle_data=1025901639) which means an international order. The other solution I've found is by RC Model Enterprises (http://home.att.net/~rc-enterprises/rcme_014.htm) but these control horns seem very pricey!

  If anyone could point me to a longer 3mm connecting arm that will fit on the MK and IM horns I'd be happy (BTW, I've used the MK BB connectors on the MK horn and they still aren't really long enough).

  Is it just me, or have others experienced this dilemma as well?

  Thanks,
  Keith Black
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