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Weld filling drilled hole in elevator horn

M

Mark L

Member
Recently I went back to the HS and elevators to drill the hinge bolt holes in the elevator control horns, using a drill bushing in the bearing. I drilled a #40 pilot and enlarged up to 1/4". However, after enlarging I found that there was not quite enough clearance to fit the hinge bolt & nut; the hole was drilled too close to the pipe of the elevator horn. After evaluating the problem, it appears to be due to slight angle in the elevator horns when they were welded. Every thing fit up well when they were fit when constructing the elevators.

I called Van's (they said this is a common occurance) and it was suggested that I grind down the bolt head a bit to allow for fit (the only interence on this side is due to the weld bead between the horn and pipe), and use a recessed nut on the bolt (allowing me to secure or turn on the hinge bolt). But, no joy; I cannot get the washer on and thread on the nut. There still is not enough clearance (maybe as much as 1/16"). An alternative suggestion from Van's is to fill the drilled hole (weld it full), grind it down flat again, thus repair the hole; back out the HS rod end bearings a bit and redrill.

This is where I am headed. I have friend who will fill it for me. However, I would like to get some advice from the group as to what welding material and method (Mig?) should be used to fill the 2, 1/4" holes.

Any knowlegable welders out there?
 
I had a similar problem. twice :eek: well two different problems,any how I filled both holes with a mig,ground them flat (I was a weldor in a former life) and re drilled the holes,

I have not flown the plane yet but it was not even a blip on the concern radar for me
 
You can weld it okay, but hardening around the old hole can make re-drilling tricky. Have you thought of making a nice divot in the washers on either side? That way your bolt head and nut stay square. Otherwise you can plug it with a soft steel bolt, re-drill, then weld the plug after or leave it. Depends on how the plug & new hole relate.
 
Back one side of the hole with a brass or copper block, clamp firmly. Warm the block enough to sizzle spit using a propane torch or something. Now tig the hole closed, working from the outer edge inward in a spiral. Leave the block clamped in place until cool enough to handle with a bare hand.

The block does two things. The plug will be flat and smooth on one side, and the block's mass slows the cooling rate. 4130 is an air-hardening steel; slow cool equals easy to drill later.
 
DanH said:
Back one side of the hole with a brass or copper block, clamp firmly. Warm the block enough to sizzle spit using a propane torch or something. Now tig the hole closed, working from the outer edge inward in a spiral. Leave the block clamped in place until cool enough to handle with a bare hand.

The block does two things. The plug will be flat and smooth on one side, and the block's mass slows the cooling rate. 4130 is an air-hardening steel; slow cool equals easy to drill later.
Click to expand...

Also gives you plenty of time to go mix a gin & tonic, and slice a lime to perfection while you are waiting.
 
Single flute bits for drilling the welded material

Buy a single flute drill bit from McMaster-Carr -- I had to have mine welded twice (first one misdrilled...the second messed up during drilling because of the hardness of the weld). Did a bunch of research and found that a single flute bit was the ticket. It went through the weld like butter! I started with #40 and then stepped it up to final size.
 
I had mine professionally filled/welded and ground down. I didn't do the welding so I don't have specifics on that. What I can tell you is that I have 350 hours on my -8 with lots of aerobatics flown between -2 and 5 g and the filled hole is of no concern. The area looks great.

Jerry
RV-8 N84JE flying since Feb 4, 2007
 
DanH said:
Back one side of the hole with a brass or copper block, clamp firmly. Warm the block enough to sizzle spit using a propane torch or something. Now tig the hole closed, working from the outer edge inward in a spiral. Leave the block clamped in place until cool enough to handle with a bare hand.

The block does two things. The plug will be flat and smooth on one side, and the block's mass slows the cooling rate. 4130 is an air-hardening steel; slow cool equals easy to drill later.
Click to expand...

Does anyone know of any TIG welders in the Kansas City area with experience performing this repair? So far I've only come across gas or MIG welders.....must be a geographical preference or something. :)

Thanks
 
Just get a new one!

How much is it worth to have a perfect one that you will have confidence in?

Each time you heat that puppy up and introduce new materials /gasses and stress into the situation, the less I would want to be flying in it.

It's a small price to pay to feel better when you hit high levels of turbulence.

It's your thing, do what you wanna do!

Now if you need different nuts and bolts, I can really be of help.;)
 
Different Nuts and Bolts??????

Tom,

I take it you would ignore the Van's recommendation to weld the hole shut and redrill, and would instead recommend removing the horn and replacing it. I think with my skills I could get the old one off ok, but the thought of trying to rivet a new one in this tight space looks impossible, and I really don't want to disassemble half the elevator for access.

In your view could a new one be mounted with structural screws or bolts instead of rivets? I had heard that Cessna had approved a wing spar repair where screws were permitted to be used in place of rivets.

Your thoughts are appreciated....

Thanks
 
I had to weld mine as well, but I used a small piece (1"x1.5") of 4130 to weld over the area and then weld the hole shut from the other side. This way it was reinforce and I had a normal piece (not hardened) to drill into. Also, make sure you use the best primer/paint method as this is steel and will rust much faster then other aluminum parts.
 
Personally

I would gas weld it.

Mainly cus i don't have a TIG and gas can be used to allow the weld to cool slowly.

I have gas welded much 4130..The easiert way would be to cut a small patch for the hole.

But I would ga weld it in a heartbeat..You may get a little distortion but that can be straightened out.

Of course it will burn off the poweder coat too.

Frank
 
Its Quite Possible.

swrankin said:
Tom,

I take it you would ignore the Van's recommendation to weld the hole shut and redrill, and would instead recommend removing the horn and replacing it. I think with my skills I could get the old one off ok, but the thought of trying to rivet a new one in this tight space looks impossible, and I really don't want to disassemble half the elevator for access.

In your view could a new one be mounted with structural screws or bolts instead of rivets? I had heard that Cessna had approved a wing spar repair where screws were permitted to be used in place of rivets.

Your thoughts are appreciated....

Thanks
Click to expand...

NAS623-2-? Screws are small and structural. They are also close tolerance.

They have a close shank and are 5/32nds in diameter.
They go by 1/16ths in grip length.

http://www.gen-aircraft-hardware.com/images/pdf/Structural_Pan.pdf

I would use the MS21042L08 nuts without a washer or some NAS620-8 washers if you have room, or just feel better with the washers.

http://www.gen-aircraft-hardware.com/images/pdf/Locknuts.pdf

http://www.gen-aircraft-hardware.com/images/pdf/nas620_1252.pdf

I think that if you get the bell-crank out and the rivets drilled out, that screws or rivets would work fine. You will be starting with new parts so riveting should be an option also.

These are just suggestions of what I might try, use em if you like em.
If not they may help another lister.
 
GAHco said:
NAS623-2-? Screws are small and structural. They are also close tolerance.

They have a close shank and are 5/32nds in diameter.
They go by 1/16ths in grip length.

http://www.gen-aircraft-hardware.com/images/pdf/Structural_Pan.pdf

I would use the MS21042L08 nuts without a washer or some NAS620-8 washers if you have room, or just feel better with the washers.

http://www.gen-aircraft-hardware.com/images/pdf/Locknuts.pdf

http://www.gen-aircraft-hardware.com/images/pdf/nas620_1252.pdf

I think that if you get the bell-crank out and the rivets drilled out, that screws or rivets would work fine. You will be starting with new parts so riveting should be an option also.

These are just suggestions of what I might try, use em if you like em.
If not they may help another lister.
Click to expand...

Tom,

This is a big help and I'm definitely interested in exploring this further. I may come back to you off-line with additional questions once I get the horn off.

Thanks again,

Scott Rankin
 
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