REFLECTOR: NOSE WHEEL GOT SIDEWAYS

[Dave Black]

Jeff, Oscar,

Pictures!

Ten years ago I first observed the nose doors staying open until the mains
were up, and then slamming. I thought I had built something wrong. After all,
from the plumbing diagram it seemed obvious the nose doors were supposed to
close as soon as the nose gear retracts. But then I watched the Velocity video
and observed the exact same thing on their demonstrator. Since then I've
observed it on numerous flying Velocities. And read dozens of case stories on
the Reflector. The gear doors operate, but not the way you'd expect or choose. 

After considerable experimentation, I determined that to make it activate, the
sequence valve requires a very high pressure on the pushbutton. The problem of
nose door slamming is directly traceable to how much effort is required to
press this pushbutton. I suspect the designer of the nose gear system never
expected the pushbutton to require such a great deal of force. 

The plans call for the sequence valve to be actuated by the ball of the shock
strut. That's approximately 12 inches from the nose gear pivot. At that
distance, there's a major leverage disadvantage, and the retracting gear does
not come close to providing enough force to push the button. Hence the gear
'bounces' at the 95% closed point. In most installations, the doors close
slightly with this bounce. The nose gear remains 95% up and the doors 10%
closed until the mains reach full up travel. At that point, the hydraulic
pressure goes high enough that enough force is provided to finally push the
pushbutton on the sequence valve. Once the hydraulic pressure is that high,
the sequence valve is opened suddenly, and the nose doors slam. 

I found the late closing and the slamming annoying, but as we've seen it can
also damage the nose door linkage. 

If you move the sequence valve to a point 2" (or maybe 3") from a nose gear
pivot point, there's ample force available to depress the pushbutton on the
first try. That's what I have done. I relocated my sequence valve to be
actuated by the overcenter linkage -- about 2 inches from its pivot point.
There's about 6x more force applied to the pushbutton there than in the
Factory location. The sequence valve (and nose doors) operated perfectly.
Trouble was, reaching this area for maintenance was very difficult. 

I could not find any other areas where the sequence valve could be pushed
directly by part of the nose gear linkage and still be less than 3" from a
pivot point. So I came up with a simple lever system, using a gate hinge with
a long arm (see photo) to operate the pushbutton. That allowed me to mount the
sequence valve in a relatively easy to reach area at the front of the keel. In
my installation, the hinge is multiplying the force of the retracting gear by
approximately 5x. The nose gear retracts fully, and the doors close smoothly
before the mains retract. 

It looks as though it would be possible to make the original Factory location
work properly simply by adding this same hinge to the pushbutton for leverage.
Likewise, using the leverage hinge the sequence valve could be located on the
front of the canard bulkhead where maintenance is simple. 

Here's a drawing of the 3 places I've located the sequence valve, and photos
of my current installation. The Factory location produces the Bounce & Slam.
The overcenter linkage location works great, but is hard to reach. The keel
front location is comparatively easy to reach and works great. Make certain
you use a very sturdy hinge, as it really does take a lot of force to push
that button. 

Dave Black
Shortwing RG
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