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

This is a weld on my spun aluminum Mooneyes 3qt chopper tank. It has a 90-deg fitting and a breather tube attached to it, but the tube just hangs, it's not attached to anything on the other end.


It's cracked right where the bead meets the tank. Is this a faulty weld? Has anyone experienced this with any of their Mooneyes tanks? I would like to buy one of their tanks for my Model A build, but if this is a typical thing I'm going to go with something else.

Please advise! Thanks!
Scooter

 

Looks to me like insufficent penetration from a cold weld. Could have also been vibration, but it doesnt sound like theres much load on it. Sooo......

 

I'd say it was a case of vibration causing the fitting to move-fatigueing the joint till it cracked at the weakest point Was the hose heavy or very long?ANother point to make is it was on a HARLEY right?
Vibration is a real problem there!

 

The hose was 5/16 I.D. and was only about 4-inches long. The tube it was attached to was just a piece of bent up brake line that was not more than about 8 inches long. I figure it couldn't weigh much more than a few ounces. Here's how it's set-up:


Sorry if this seems off topic, but ultimately, if I hear from you guys this is a typical thing with Moon tanks then I won't be buying one for my Model A.

 

chances are those are factory welded by a machine, and machines do make mistakes if improperly setup...if that's the case then why not contact moon and see if they would repair/replace the tank for you?...considering you're a potential return customer, I'm sure they'd be more than happy to keep you happy (and keep your money coming in)...

 

There doesn't look like any thing wrong with the weld. The parent material next to the weld failed. Two possibilities as I see it, Improper pre heating prior to welding or metal fatigue or a combination of both.

 

It's probably a combination of things.

1-Vibration,with the tube not being supported.
Rigid frames are bad for vibration.V-Twins vibrate.
Go figure.

2-The tank is much thinner than the bung welded on ,
the transition between the two is too sharp,creating a stress riser,
where the thin tank met the heavy weld.

It would have lasted longer,if the weld was washed in better.
and the breather tube supported.Better yet,get rid of the steel line.

 

They don't look like robot welds to me but machines do fuck up a lot. It might've had a shitty robot weld on it to begin with and somebody just went over it again but did a shitty job themselves. It might be that the 2nd pass is just peeling up due to poor penetration...does it leak? I don't have any first hand experience with MOON and this is the first bad thing I've heard about their tanks but even experienced welders can sometimes lay a bad bead-especially in a production setting where it's always GO-GO-GO!

 

it would have lasted longer,if the weld was washed in better.
and the breather tube supported.Better yet,get rid of the steel line.[/quote]
I agree get rid of the steel line or at least isolate both ends of the steel with rubber, may sound silly but the weight of the rubber line filled with oil is acting as a lever on the line, especially in a rigid frame, and it's fatiguing the weld. My 2cents. FWIW looks like Triumpf or BSA (inline twin) and they don't vibrate near as much as a Harley Vtwin.

 

That bike is a paint shaker for sure! LOTS of vibration! It very well could be just from vibration or a combination of weld/material failure and vibration. I've never heard anything bad about these tanks either.

As far as I know, they weld these by hand. I know they have someone just to make the spun aluminum halves. I'm pretty sure someone welds these up by hand and not by a robot.

I talked with a guy at Mooneyes this morning and sent him a couple pictures. He's having me send it back. Not sure what they can do with it, but hopefully we can come to a reasonable decision about what to do. I'm willing to pay for a repair if how I set it up caused it. The funny thing is, I have steel lines mounted all over this thing (all with rubber interfaces) and the rest of the bungs look fine. Why this one... Voodoo!

I really like the Mooneyes tanks and I will probably buy another one to hold my precious gasoline in the A. Mooneyes has been good to me so far and I can't complain too much.

 

This is pretty common with dissimilar alloys and poor welding. The tank itself is most likely 3003 Aluminum and spun into the tank shape. The bung is problably 6061 and god knows what material they used as filler. Too much heat and to rapid of a travel rate caused the weld to be brittle. Annealing would have prevented or at least prolonged the crack. But the real solution is welding properly.

 

First thing that popped into my mind was hydrogen embrittlement....

 

Material failed next to the weld because of the vibrations created by road, motor, fat chicks

 

not enough penetration to the surface material

 

Hydrogen embirttlement is ususally assciated with chrome plating or other electric deposition processes. Unless the tank was annodized I thing we could rule that out.

I have had a few Moon chopper tanks here. All have had better looking welds than that one. One has been on the bike now for two years of nearly daily use and was just on the Diablo Run. No failure...


Bad weld pure and simple.

 

From what I see the hard line is not supported and is acting like a lever with the vibration of the engine.

 

From what I see there is nothing wrong with the weld. It held up just fine. The tank material cracked next to the weld.

 

being unedjumacated about welding asside from shitty MIG boogers, my first guess would be the same....the tube is long in comparison, and solid, and if its vibrating even a little bid i can see it putting stress on the bung...

why not the others? .............yet.

if vibrations caused that bung to go....ill bet ya a dollar that within a year your oiltank is going to come crashing down at 70mph due to the shitty mooneyes mounts. those mounts are REAL brittle. especially hanging upside down like that.

 

I think it might have something to do with insufficient cleaning of the base metal. It doesn't appear to have much if any penetration. Either they didn't clean it manually, or they didn't have enough time in the EP part of the cycle to get adequate cleaning.

 

DUDE! You're scaring the shit out of me!! Don't send me bad Juju bro! I'm convinced this bike is jinxed! At least this is the only thing left on the bike to be repaired.... OH MAN! Now I did it! Now I'm going to have AT LEAST 10 more things go wrong!

The tube actually weighs less than the hose and bends quite easily.... however... the hose could act like a pendulum weight. As the bike is shaking maybe the frequency of that tube is just enough to fracture that weld. The other tubes are pretty well supported by the motor itself. Technically put... simply supported at both ends and the breather tube is not supported and only cantilevered from the fitting.

I definitely am still questioning the weld though. If the weld were questionable and just hanging on by a thread, any side or lateral load could have caused it to fail. I guess what I'm saying is, maybe the weld was bad, but the poorly mounted tube caused it to surface. Two bad things led to one big problem!

 

ask fab kevin about those moon mounts man,seriously, its the reason he makes them now..... no joke. no juju just lookin out. i dont think they really were meant to be mounted like that especially on a vibrating triumph haha. next time you take the tank off feel how light they are.

go with something like this or this



or make your own set...


i thikn your right on the pendulum. its stiff, (i just said its stiff huh huh) and im sure its vibrating like crazy and the vibrations are going right to the bung..im not saying thats what did it because im not a welder, but i know it couldnt have helped. at least if it was rubber it wouldnt vibrate so much.

the tube is ugly anyways IMO. would look better with just a hose breather.

 

It's simply overpenetrated into the thin tank material. It's common when tring to weld a thick bung to a thin sheet. You have to floor it to get the thick flowing, and stay off the thin at the same time until it's ready, which is hard, because in a corner joint you can't hardly direct the heat off of one piece and onto the other 50% more, then drop down into the thin just right and start adding filler, it's a trickier weld than it appears, it takes just a split second to melt half the thickness of the sheet away, you're trying to run 75% top heat but only 25% bottom, it's hard, when you get laxed and accidentally run 60/40 or 50/50, you get what you've got. Even though the undercut isn't as visible as it is sometimes, it's there. It made it thin enough at the edge of the weld that your situation/forces of vibration, the fitting, etc.,was just too much for the reduced thickness. Didn't have anything to do with the things mentioned above IMHO anyway. The weld just undercut too deep into the sheet. The answer to your question is, yes, it's a faulty weld.

 

I agree, cold weld. When the parent material is not pre-heated and is welded cold, the cooling of the welded part will pull away (crack) just like yours is cracked. I've seen it, and my teacher did it to demonstrate cold welds. You can usually hear the aluminum crack as it cools.

Cosmo

 

WOW! That's a hell of an explanation! Thank you! I was hoping someone would bust out with a killer bunch of tech stuff! Cool! Makes sense too!

Caffeine... all good brotha'! Your warning is taken seriously and thanks for looking out for me! I've heard that before about those brackets and I have seen the Fab Kevin stuff and it's SUPERIOR!! He's a killer fabber! I've been keeping an eye out for cracks and such on the brackets for exactly that reason. So far so good. You don't like my tube?? All good man! I was trying to match it up with the oil lines. Might now have been such a hot idea.

Thanks everyone for the input. Now it's up to Moon to make the decision. Just wanted to be more educated when it came down to dealing with the situation and Mooneyes. Maybe they'll see it as bad product and take care of me.... or maybe they'll fix it and send me the bill! Either way, it will be cheaper than buying a replacement. On with life in the mean time!

 

Caffeine... BTW... what the hell ever happened with that pitman arm and your cowl steering? Update that post if you could. I was really wondering what ever came of that. Thanks again man!

 

never did anything withit yet. shortly though as weather is nice.....im just going to extend mine a few inches and get the tires balanced it should be good to go. like i said it wasnt "bad" but it could have been better. im just hoping it doesnt get worse, but with a balance and leveing out the steering i cant see how it cant.

ive been too busy with my triumph and i was out of the country for 2 weeks too...

 

No the busy feeling! Trying to get this Triumph back up and running and I'm also trying to strip a Model A down and get parts ready for selling. I need to get a whole rolling chassis and everything but the body (fenders, hood, grille, bumpers, etc.) out of my garage within the next month or so.

Keep me posted on your cowl steering.



Thanks again everyone for your input! Much appreciated and I'll keep this post updated on the repair. Cheers!

 

Vibration is a funny and mysterious thing.......Like Harmonics really-
Nickolai Tesla once told a crew of workers demolishing a tall New York City building peice at a time ,that he could do the job easier and faster by using a METRONONE .....
The crew told him he was crazy.
He attached the small swinging pendulum like device to the side of the structure and in a couple of days the building was shaking and swaying bad enough that the workers asked him to remove it.....
Probably a bad weld though!

 

As the officiall HAMB metallurgist, i am just seeing this post. I agree with Roost, it has undercut at the edge of the weld and the vibration of the hanging tube caused a fatigue crack. The vibration with the stress concentration of the undercut is what contributes to failure.

It is not hydrogen embrittlement, alum is not susceptible to HE. He affects high strength steel parts (mostly).

To fix your problem, run a short support for the free hanging tube, or put a short rubber hose at the fitting.

 

Good story I like stories like that!

38/454, thanks for your input. Once the repair is made, the breather will be simplified and replaced. Will probably use something less likely to vibrate.

I started up the bike tonight and took a look at the tube vs. the vibration and noticed very little vibration, but that's not to say that when the motor is under load or bumping down the road that it doesn't jar all over the place. The tube will be replaced.