WD-630-1 Nose Wheel Fork... Cracks in the Welds

Anyone seen this before?











This is from a friends RV6-A with the updated version of the nose wheel fork. Needless to say finding this scared the poo out of him and me since I ride in this plane often.

He treats his nose wheel like it is an egg and rarely takes it off pavement. I think he has somewhere around 800+ hrs on it now.

CRacks

Wow ! Good find . Curious from one of the welding pros on what caused this

Darn, I first though there is now way this could crack but after looking at the rest of the pictures I agree it looks like the weld is cracked. Time to call Vans on Tuesday. Gonna check mine too!

There was an SB on checking for cracks in nose wheel forks some time ago. However that SB is not about cracks in the weld but cracks at the bend. Not sure if this pertains to the later version, but a good idea to check anyway. Read here:

https://www.vansaircraft.com/pdf/sb96-09-1.pdf

Cracks in the weld

What I see here is typical embrittlement of filler rod vs the base metal. It's common when the filler rod and base metal have different numbers. It's kinda like trying to weld 2024-T3. My suggestion is taking it to an experienced aluminum TIG welder and have it rewelded using 5606 filler rod with a lot of heat on a square wave machine. I would bet Rick Robbins of Robbins Wings could rewelded it and not crack again. Vetterman

He is calling Van's today to inform them. I think he is planning to purchase a new fork to get back in the air.

He has a new one on the way. Van's requested he mail this one back to them for an investigation....

Cracks down each side of every weld???
I do expect it to be something other than cracks.

Anyone run a dye check on it to see if they are actually cracks?

gasman said:

Cracks down each side of every weld???
I do expect it to be something other than cracks.

Click to expand...

RVDan said:

Anyone run a dye check on it to see if they are actually cracks?

Click to expand...

This can be a common issue if the wrong filler rod was used. Larry commented on that above and other examples are out there on the web.

These are not traditional fatigue cracks that normally would run right down the middle.

Maybe Van's will post their results after they do their dissection....

Update to this thread....

The friend dye tested the fork for cracks and could not find any. Van's still wanted it back to do their own test. He just heard back from them and they did not find any cracks either.

Have no idea what those lines are that show up when the welds are cleaned but apparently they are not cracks!

Brantel said:

Update to this thread....

The friend dye tested the fork for cracks and could not find any. Van's still wanted it back to do their own test. He just heard back from them and they did not find any cracks either.

Have no idea what those lines are that show up when the welds are cleaned but apparently they are not cracks!

Click to expand...

I don't know for sure either but I have a theory......

The temp will not ever cool at exactly the same rate across the entire heat effected zone of a weld.
Particularly in a case like this where there is a lot of thermal mass and the weld bead is rather large.

I think as the weld bead cools the actual weld surface can end up having a slightly different surface texture/porosity across the weld.

In this case, the parts exposure to very fine dust and it being coated to just the right thickness, the surface texture of the dust looked slightly different on the edges of the weld bead than it did down the middle.

I did the second die pen. inspection (from my understanding it was actually the first), and with the part clean and shinny, with the naked eye it wasn't possible to see a surface texture difference, but I think the dust made it show up.