REFLECTOR: Steel Aileron Torque Tubes

[Brian Michalk]

What follows is not a recommendation on a steel tube:
If I were at this point, I would make a design change here.

Look at the pivot of the control stick to the torque tube.  All of the 
torque is sent through a -3 (I believe) bolt that needs to be tightened 
enough to remove play, but loose enough to allow rotation.  It's a 
design that I wish I would have addressed.  If I were to do it over 
again, I would:

1) Run the torque tube in the center of the keel, which may displace 
your speed brake actuator.
2) attach it with the provided hardware to the top of the keel. The 
forward bearing would be just aft of the control stick cutout, leaving 
three or four inches extending (cantilevered) past the bearing.
3) using a larger ID tube, make an adapter that will slide over the 
torque tube such that the torque tube pierces the adapter at a right 
angle.  The control stick will be inserted into this adapter.  This will 
be drilled and will transmit torque from the stick to the torque tube.  
The hole in the adapter will necessarily be longer along the stick axis 
in order to rotate in pitch.  Alternatively, one could weld on some thin 
steel that would sandwich around the torque tube, which is easier than 
machining an oval hole in a tube.
4) Because the pivot point is very close (higher) to the keel cutout, 
your keel cutout will need to be smaller to provide the required control 
stops.  I haven't done it, but you can do the math.

Using this design, the pivot bolt is only in shear, and not in torque, 
which is the main difference from the plans.  I believe you will like 
the feel of this design better than the design from the factory.

The other benefit is that the design is symmetrical.  The factory design 
is such that when the stick is moved left, it raises and is allowed to 
impart more left aileron.  When moved right, it descends into the cutout 
more, contacting the keel cutout earlier, resulting in less right 
aileron deflection.

I did machine a saddle that provides for one square inch of bearing 
surface, but still don't like the behavior.

On 3/23/2014 7:38 PM, Paul Folkes wrote:
> Hi all,
>
> I was flicking through the wiki and read about the supposed issues 
> with the standard aluminium torque tubes warping.  As I am near to 
> bonding the keel in permanently, I would rather address this issue 
> first.  Is there a problem with the alum tubes warping? Is the steel 
> tube upgrade worth it, or am I looking for a problem that may not be 
> there?
>
> Thanks,
>
> Paul Folkes
> XLRG
> VH-VVX
> /Building but a looong way to go!/
>
>
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