ATTN WELDERS! Please tell me what happened to this weld...

i have the same tank, and went through two of them for the same reason,...but on the 3rd one, i cut out the bungs and welded my own. works great now (not really enough oil for hot ass arizona though, not for a pan at least)

 

It's cracked in the HAZ (Heat Affected zone). Bad weld and the tank appears to be too thin. Someone mentioned they thought it was a Harley, but an old Triumph like that vibrates as bad or worse than a Harley.

Unless Moon starts using thicker material, I'd never use one of their tanks on my Triumph.

 

Aluminum, unlike steel, has a LIMITED FATIGUE LIFE. On a long enough time line, every aluminum part will eventually destroy itself. Your problem is the vibration pushed the tank past its fatigue life well before you expected it to. David

 

The HARMONICS on that piece of tube...Not Good!

 

Did you take the close-up from the other side than the wide shot? Is the crack on the front or the rear side of the bung?

My thought is that it was the mass of the connectors acting as a pendulum -- especially if the resonant frequency of the pendulum happens to be in the same range as the engine's vibrations.

I've seen lots of welds fail that way.

Add to that what the others have said about undercutting, etc. and there's plenty of blame to go around.

In steel it often happens because the surronding base metal didn't get hot enough for some "recrystalization" that improves the transition area from weld filler/base metal blend to pure base metal.

Can't tell for sure without cutting it in half and looking REAL close.

I'd bet on Moon sending you either a new one or the old one that is welded really well, but they could claim that this was an "nonstandard" application, etc. They make them as light as possible for the racers and figure the rest of us will just "make do". Who knows, time will tell.

Whatever happens, I'd ditch the brass connections for something lighter.

just my too scents!

 

Cracks are on both the front and back of fitting. Just the sides are keeping it together.

I don't think the brass fitting is the problem People run brass fittings in these things all day long and don't have this kind of problem. If anything it's the tube vibrating to resonence and fatigueing the weld that may or may not be faulty. I suspect both vibration AND faulty weld.

I will be curious to see what Moon will do. The tank will go back next week. If the guy that I talked to is at VLV next weekend I may just hand it to him personally. Save on some shipping.