[jumpinjackflash]

I have learned something a little too late. I have read that bending molly sheet it likes to be bent against the grain of how it was rolled with a large radius. So....I have a set of 4 very important fittings that are bent with the grain / along the grain. They have also been welded at this bend in a few spots just to tie the pieces together. Question is have I messed up and ruined the parts? Or seeing as they were welded not to worry of crack that may or may not be present? From my understanding that the act of bending along the grain sets up too much internal stresses in the metal and aids in the material opening up on the bend line outside radius. Slap me silly for not knowing this......Is this is a deal killer or do I have to pull all the rabbits out of the hat to fix this mess up. What do you guys think about this? The radius was 3T on the outside pieces. More like 1T for the inside piece....that one worries me a bit. Think lots of holes drilled to match another part.....dang near impossible to make another fitting and get it to align with the old parts.

[Otto Nobedder]

I seriously doubt you've done any harm.

Examine each hole and any other access you have with a magnifying glass. Dye-pen test if/where you can, to rule out micro-cracks.

If you still have doubt, "normalize" it. I doubt you have an oven big or hot enough to truly "normalize", but you can treat the bent metal to "post-weld heat treatment", even where it's not welded, for the same stress-relief effect.

Steve S

[jumpinjackflash]

Thanks for the reply....but there are just some things that you can't help but worry about. This would have driven me not to fly this plane or let anyone else.
Not to step on anyone's knowledge base.....but I am a worry wart. So I dug deeper into metal fabricating for aviation. These brackets attach the lift strut to the main spar....if they fail...all the fun will be released. That tends to concern me.....specially when it's me riding in there. So I sent a note to EAA tech gurus. Here is what I was told...another learning adventure. Just wanted to share since there is not a lot of info out on the web and safety is the goal here. Remaking the brackets for the simple fact that I would hate to be an un-invited lawn dart

From EAA.........

Here is a link to a chart showing bend radii for both Aluminum and Steel: http://www.bjg-design.com/designbook/shbend.htm

According to the table, A 1T bend radius for .040 4130 steel would be too sharp - the minimum bend radius for a 90 degree bend for .040 is .125, which is actually 3.125T.

In addition, bending with the grain is to be avoided, if possible. Sometimes in a complex part you may not have a choice, but cracks develop much easier than when the bend is with the grain.

Here is a link to use to search for EAA technical counselors in your state -

https://www.eaa.org/en/eaa/aviation-com ... or-program

Regards,

Tim Hoversten, EAA #598743 - Private Pilot, ASEL
Technical Aviation Specialist
EAA-The Spirit of Aviation

http://www.eaa.org
http://www.eaaforums.org

See you at EAA AirVenture Oshkosh 2014 - July 28th to August 3rd

[Otto Nobedder]

It's a good thing you checked on it. I wasn't thinking "airplane" when I replied. Odd, since we've chatted about your build before. If I'd realized, I could have dug out my library of EAA books. I'm pretty sure one of them cavers this topic. Most of my books cover building in wood & fabric, but metal bracketry can't be avoided (unless you want to fly on mortise and tenon joinery... )

It's a good reminder to me that there are times I should check my "facts".

Steve S