The Murphy Builders Site

----- Original Message -----
From: "Rebel" <rebel@dcsol.com>
To: <mike.davis@dcsol.com>
Sent: Monday, January 18, 2010 6:15 AM
Subject: Instability

Hi
I own a Rebel series 615-R, equipped with 2.2 liter Subaru engine, with
serious stability problems while on ground.
-During taxing, tends to move to the sides.
-While on take-off run, at full engine, the instability diminishes and its
possible to take-off without problems.
-But, if during the take-off run the power is cut, the plane becomes
extremely unstable and it becomes impossible to keep it going staight on
the
runway. Generally it ends up off the runway looking to where we were
coming
from.
-To sump it up, if the plane is at speed but without traction it becomes
completely unstable while at ground.
-Ive got experience with planes of conventional layout, but its the firs
time
Ive met such an unstable one. The rear wheel is in perfect conditions and
has
been recently lubricated.

Is there a special aligning for the wheels, some specific tire pressure or
some
other element I should check or modify ??

Thanks
Albert

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Albert, what's on it for a spring and wheel? Sounds like the wheel has
negative castering (tilted back) and possilby a soft spring. It wants to turn
left or right as it passes thru center and accually tilts the spring from one
side to the other . Look at the angle of the top of the wheel assembly
(steering arm) when there is weight in the plane. Get a couple of guys to sit
in it. It shud be parrell with the ground or better yet, tilted back ever so
slightly. Also I have mentioned that I originally used the outside rudder arm
holes for connecting the chains. I ended up with an over controling situation
in this position and went back to the inside holes with a fair bit of slack in the
chains. Had to machine/shorten the locking pin to get it to swivel. Not a
problem now.

Steve W. 637R




nOn 1/18/2010 7:24 AM, mike.davis@dcsol.com wrote to rebel-builders:

->
->
-> ----- Original Message -----
-> From: "Rebel" <rebel@dcsol.com>
-> To: <mike.davis@dcsol.com>
-> Sent: Monday, January 18, 2010 6:15 AM
-> Subject: Instability
->
->
-> > Hi
-> > I own a Rebel series 615-R, equipped with 2.2 liter Subaru engine, with
-> > serious stability problems while on ground.
-> > -During taxing, tends to move to the sides.
-> > -While on take-off run, at full engine, the instability diminishes and its
-> > possible to take-off without problems.
-> > -But, if during the take-off run the power is cut, the plane becomes
-> > extremely unstable and it becomes impossible to keep it going staight on
-> > the
-> > runway. Generally it ends up off the runway looking to where we were
-> > coming
-> > from.
-> > -To sump it up, if the plane is at speed but without traction it becomes
-> > completely unstable while at ground.
-> > -Ive got experience with planes of conventional layout, but its the firs
-> > time
-> > Ive met such an unstable one. The rear wheel is in perfect conditions
and
-> > has
-> > been recently lubricated.
-> >
-> > Is there a special aligning for the wheels, some specific tire pressure or
-> > some
-> > other element I should check or modify ??
-> >
-> > Thanks
-> > Albert
-> >
-> >
-> >
->
->




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