Fitting Elevator Horn TO 3/4" Rib Tube

 

After welding the shells together I wanted the 3/4" rib tube to be as close as I could get it centered between the cable holes, in the tabs, and square to them.  I clamped my combination square to the tabs, centered on the inboard edge of the holes.  The holes are 3/16" dia. so I used a 3/32" drill shaft to position the edge of the scale along the centerlines of the holes.   Then with the square positioned on the center, or one of the edges of the tubes I was able to layout guidelines on the shells.

I then Filed the 3'4" hole to the lines so the tube would start about 1/8" into the hole from the edge of the shell.

I didn't want to file the holes to a perfect  fit, so I tapered the end of a piece of 3/4" steel rod.  The idea was to tap it into the hole to bend the shells out slightly.

It worked perfect.

Then I used a leather mallet to flatten the shell slightly around the rod.

After doing this it looks like they did about the same thing on the factory part.

The hole is now very round and fits the tube snugly.

I rounded the end of the tube slightly so it wouldn't scape the shell going through the hole.

The last thing was to file a curved recess in the end of the tube so it will fit tighter to the spar tube for a little better weld strength.  My hope is I can pickup the end of the tube in the weld of the shell to the elevator spar.

I have a half round bastard file which has a 1/2" radius for filing the recess.

I like the way it fit together.  Now I have some welding to do.  I'll fit up the second one before welding.