REFLECTOR: Gear Forks

[Tom Martino]

I heard if you chrome aluminum (as in the nose fork) it can cause it to
weaken.  Any thoughts?  It would sure dress it up and I was thinking of
doing it.
 
 
-----Original Message-----
From: NMFlyer1 at aol.com [mailto:NMFlyer1 at aol.com] 
Sent: Tuesday, June 15, 2004 7:52 AM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Gear Forks
 
The casting flaws are the rough appearance in the surface of the
material. The most detrimental are the ones on the edge, in an area of
particular load and/or vibration. 
Almost everything has casting, machining, or assembly flaws. Spam-can
builders take lots of time de-burring all the holes they drill, and
dressing the edges of every piece of aluminum they cut. this practice
does not insure against a stress crack, but greatly reduces the
possibility of it. 
 
The same care should have been taken on installation of the Plexiglas
windows as well! 
 
The (quite pricey) block on my 4.3L chevy needed some attention to
relieve stress points (casting flaws) in the crank webs. Again...
insurance. 
 
Not to say that a nose gear fork would fail if it wasn't polished, but
it will sure help it last to do so. 
I would guess that the design of the "old style" fork could have been
sufficient if it was designed on a billet cut piece (which have flaws of
their own), or on a polished or better cast piece. The only problem is,
that adds a LOT of cost. Increasing the thickness of the piece can aide
in reducing stress cracks, but polishing it will help even more. 
 
At a materials stress demonstration, the speaker took a piece of
aluminum that was 2" wide, about 8" long and 1/4" thick. He scratched
the surface with a pocket knife in the middle, then began his talk. As
he was talking about materials stress, fatigue, etc, he was gently
flexing the aluminum bar with his hands. Im not sure how long it was,
but well into the talk, the 1/4" bar broke in half, right at the light
scratch that he placed on the surface. Stress Crack run amuck!. 
 
There are many areas in construction of the velocity that will benefit
from some polishing attention:
Basically every aluminum part that you put in the plane, but specially,
bell crank brackets, canard hinge arms, hinges, rudder arms, nose fork,
etc. 
 
I polish out my pieces with a scotch brite wheel on an angle die
grinder. Use the finest wheel you can get away with. Gently take the
sharp edges off of the corners, buff out deep scratches, de-burr the
holes, etc.   
 
This practice will pay you back in longevity. 
 
 Kurt Winker
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