REFLECTOR: NOSE WHEEL GOT SIDEWAYS

[Tom Martino]

When I first started this thread ... I originally thought my nose gear had somehow gotten sideways and it snapped the "T" fitting on the end of the door actuator.  I later came to the conclusion through much testing that this was NOT the case.

I believe the cause of the broken "T" fitting was the nose doors "slamming" as described by Dave Black.  In fact, I totally agree with Dave's analysis of the gear retraction system and the force needed to actuate the sequencing value.  It describes perfectly the problem of "slamming doors".

I have installed a flow restrictor in the fitting at the bottom of the door actuator - which has solved the problem.  I have also found that springs which hold the doors "open" help with smoother closing. 

The slamming did not appear to be a problem ... but I later found that it stressed the gear door rods and "T" fitting.

Tom
N173EX



  

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On Behalf Of Dave Black
Sent: Monday, March 21, 2005 11:54 AM
To: John Dibble; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: NOSE WHEEL GOT SIDEWAYS

John,

> My sequence valve is mounted in the nose compartment and is activated by
> the gear leg near where the bend is.  First my nose gear retracts 95%,
> then the doors close 95%. After the mains retract, the nose gear fully
> retracts and the doors "snap" shut.  It doesn't seem like slamming and
> I am happy with it.

Most builders have mounted their sequence valve farther from a pivot than
yours, and get a very definite 'slam'. And most builders don't seem to mind
that their nose doors slam.

>From your description, it sounds as though your sequence valve is <almost>
close enough to the pivot point to work as intended. Probably if you moved the
sequence valve 1/2 inch closer to the pivot everything would close 100% on the
first try.

To test this theory, try the retraction test I described. When the nose gear
gets to that 95% up position, manually pull it up the rest of the way. If the
nose doors close completely as soon as you do that, it demonstrates the
sequence valve was not actuated fully. That can be traced to insufficient
force on the sequence valve's pushbutton due to the sequence valve being too
far from the pivot. 

I'm not suggesting you change your sequence valve location -- especially since
yours closes 95% on the first try. But I thought you might be interested to
see what a little extra force on the sequence pushbutton will accomplish.

For me, the really surprising thing was how hard it is to depress the sequence
valve's pushbutton once the hydraulic system is pressurized. After all, it
operates with light finger pressure when it's just sitting on the workbench.

Dave Black
Shortwing RG
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