how to install robart pin hinges

 

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Procedure by: Gary Mills

Drill a hole that is just barely undersize so that the barbs on the hinge rub when the hinge is inserted.
Take a wood dowel about three inches long and turn about two inches of it down so it is just a little smaller than the hole you made. Keeping the other left over inch of the dowel just a little larger than the knuckle of the hinge.   You are going to insert the dowel in the drilled hole.  Forcing the enlarged area in about 1/8 of an inch creating an enlarged area for the knuckle nestle into.

Rough up the barbed area of the hinge with 60 or 80 grit, just a  little to take away the smooth plastic look.
Take some motor oil  30 or 40 weight and put about a teaspoon out on a smooth surface.  It will flow out making a little pool that will be about a 1/64th or 1/16th deep.    Take the hinge and fold it to it most bent position forming an L, lightly touch the knuckle into the oil, reverse the L and do the other side.   Unfold the hinge and work open and closed two or three times.    Take a Qtip or tooth pick and wipe off any globs or     excess oil, you just a thin film around the outside of the knuckle but you want the joint of the knuckle to look well oiled.

Bend the hinge back to the L position and lay aside.  The L position keeps them from rolling around and getting the oil on the barbed section which is a no no.

Some people use Vaseline to lube the knuckle but it is to slow for me.

Mix your epoxy and thicken with what ever you use.   Take a thin round whatever and use it to coat the walls of the hole you drilled.   Do not try to fill the hole with epoxy because you are just going to push it to the inside of the wing with the hinge.  Now coat the barbed area of the hinge, load the barbed area so that it looks level all one diameter all the way out to the tip.   Insert the hinge, it will help the epoxy to go down into the hole by twirling the hinge one or two revolutions as you are inserting it. Other wise some of the epoxy will squeeze back up out of the  hole.  If it does have some  toothpicks ready to wipe it away and keep it off of the knuckle.   Any epoxy that does get around the knuckle can be cut away later with an xacto, it want stick if you oiled the knuckle.

I do all the hinges on one side of the surface first.  It is important for the hinge pin to be aligned (the same depth) into the surface as all of the other hinges.  I usually split the pin or brad with the out most part of the bevel on the surface they are being inserted into.   Let the hinges all lay over into the most deflected position this helps you get an ideal if they are folding at a 90 degree line to the surface they are in.

Now the fun part, putting on the other surface ie elevator or aileron.   Dope up the hole the same way.   Put a little less epoxy on the barb part of the hinge.   Put the elevator down onto all of the hinges and insert about half down the hinge.   Check for epoxy being squeezed up out of the hole.  If not add a little  epoxy to the barb with a tooth pick.  Push the surface down further.   Your goal is that when the knuckle area is just bout to seat in the hole very little epoxy is still there that will have to be cleaned out.  I usually run tape around the surfaces to control the gap.  I like as little gap as possible but remember depending on how you beveled your edges the smaller the gap the less surface deflection you are going to get.

  

After all has dried it is not uncommon to have the surface slightly glued.  With a little force it will break free

This sounds very complicated but it is not a big deal after you get comfortable with it.

Never had a hinge pull out