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

[Ed Deaver]

Keith, Art Wagner and some of the N Dallas guys have used an offset on the 
servo wheel to overcome the slack that occurs when the clevis isn't at the 
hinge line.

He used a large servo wheel and glued/bolted another straight servo arm, but 
not at the center where the bolt would go through both.  He used a series of 
trial and error to get a no slack situation with the wires.

I have never worried about the slack on the non-pulled side personally.  
Long as both sides are tight at neutral.

Ed


>From: "Keith Black" <tkeithb at comcast.net>
>Reply-To: discussion at nsrca.org
>To: <discussion at nsrca.org>
>Subject: Control horns, is it just me or... ?
>Date: Tue, 2 Sep 2003 20:57:17 -0500
>
>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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