24 January 2014

On The Outs

The Sight Unit Infantry Trilux L2A2, aka SUIT, aka Trilux is externally adjusted for zero in both windage and elevation.  The long range setting also affects things outside the sealed optics.

With the range lever to the rear, the sight is set to short range.  0 - 250 yards with Dottie.  The "round things" (from L to R) in the pic are the R with an Arrow on it knob for windage the back-up rear sight.  Then the crusty lever pointing to 11 o'clock is the range lever and its barrel.  Then the Trilux's windage screw.  Then the rear mounting screw for the mount.

With the range lever set forward, the sight is set to long range.  430 yards or so on Dottie.  The big round barrel the lever rotates brings flat spots to bear on the base.  They are different distances from the center of the barrel, so they change the elevation of the scope when the lever is thrown.  To the right of the barrel is the windage adjustment screw (with the 8 radial lines around it).

This is the elevation screw for the scope.  The screw to the right is a locking screw for the elevation adjustment.

The underbelly of the SUIT.  On the left you can see the flats for the range adjuster.  Then the saddle bar for the windage adjustment (left of the red screw).  The squiggly wire is a spring that holds the scope against the mount.  Then all the way to the right is the elevation screw.

Close up of the elevation screw.  Notice that it's a cone?  This is so changing the windage at the back doesn't change the elevation at the front.

The mount.  On the left is the t-bar that gives the range lever's barrel something to sit on.  The round post is what the windage's saddle bar bears against.  The shark-fin looking hook is what the squiggly spring pulls down against and the v-notch to the right is what the elevation screw's conical nose sits in.

One great thing about how this was designed and executed it that the scope will retain zero even if you remove it.  The key is really the cone in a v-groove and close tolerances on the windage saddle bar...  It insures that the scope goes back to the same place every time.  Not obvious in the design is how few of the mount's dimensions are critical.  The V simply needs to be made so there's just two points of contact on the cone.  The round post is critical in that it needs to hold against he saddle bar without movement and the flats on the t-bar need to be parallel to the ground and flat to each other so adjusting the range doesn't tilt the scope.  The hook has a lot of tolerance in its dimensions because the spring compensates for it.

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