Welders, waterbox....

[Vumad]

I designed this waterbox and had it built. I blew it apart almost immediately.

It uses .060 aluminum. It has baffels but not going to explain how they are setup. It's possible they create too much back pressure but the boat made good power for the few moments before it started leaking exhaust. I ran it with the hood off and had good power but then completely blew it apart. You can't see it but the long weld on the right is split about 4".

Before I go to the shop that built it, I'd like some comments about the quality of the welds. Or if it's more likely that the metal was too thin or the back pressure was too high.

Personally, I want to blame the welds, but I'm not very experienced with metal working.

 

[Vumad]

A friend has suggested it was a backfire. I do not believe the ski backfired. Also, this started as a very small leak. We couldn't find it so I kept riding the ski hoping to leave a residue. It progressively and rapidly got worse.

 

[DAG]

Did the box break on the high pressure side of the baffle or low pressure side? It's very hard to tell from pics if welds had penetration

 

[Vumad]

High pressure side. the long side that you can't see is on both sides of the baffle.

 

[cudaben]

Bad weld is my guess. Was it mig welded?

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[cudaben]

Had this happen at our shop once. Had used some old aluminum wire. Sat around the shop for a while and had corrosion on the wire, light white dusting. Every weld looked good, had the job powder coated. Put stress on the welds and they all came alart. That was a $7000 mistake.

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[Grouper]

That bead doesn't look right to me, like the weld didn't get proper penetration.

 

[cudaben]

I am on my phone, is the weld not busted down the center of it?

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[eastcoastjumper]

That shouldn't of broke if it was welded proper. Weld broke right down the center

 

[EfX]

Lack of penetration when welded, or bad wire, probably needs a flange, butted welds on thin material will blow out before proper penetration more often than not. Just my .02
Curious to see how you plan to repair it.

 

[Vumad]

Plan a is to take it to the shop that did it and ask them what they want to do.

Plan b is to take it to xmetal and see what they say about welding it.

Plan c is wrap it in fiberglass. I can do fiberglass. Then ill run it until it blows apart, or i decide im happy enough with my design to have it rebuilt.

 

[LimitedSlip7]

The weld definitely looks too cold. Do you know what alloy they used for the base and filler? It almost looks like they didn't use any filler at all...

 

[Schmidty721]

Is every seem welded? When I build a box I use two bent pieces. Side, bottom, side bent from one piece, end, top, end bent from another. Maybe not an option with your design

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[Vumad]

Is every seem welded? When I build a box I use two bent pieces. Side, bottom, side bent from one piece, end, top, end bent from another. Maybe not an option with your design

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Yes, all of them are welded. I drew and cut the pieces myself to save money. I also made some slight changes once I cut all the pieces and laid them all out. You know how things are just different in your hands. The only expenses in this project were the metal (about $20-30) and the welding ($100). The design would see additional changes if I decided to produce them. Right now, I am only making and testing parts for my personal use.

 

[Vumad]

The weld definitely looks too cold. Do you know what alloy they used for the base and filler? It almost looks like they didn't use any filler at all...

That I do not know. The shop was recommended by a co-worker. I have to work tomorrow so I wont get to talk to them until wednesday.

 

[speedysprocket]

I think if the welds were good, the base metal would have torn, not separated at the weld..

 

[Vumad]

The owner of the shop is having the damaged areas repaired and the rest inspected. He said that the weld had good penetration but his body language suggested otherwise.

I guess I'll see how things are when I get it back. If the welds are basically the same, I'll wrap it in glass, and look for a new shop to do the welds.

I was hoping this shop would work out since they were so willing to work with me on prices. I honestly expected to make changes anyway and was hoping for flexibility towards future business.

 

[High Speed Industries]

In theory the weld should be stronger than the metal around it.
If the crack appears near the weld = bad or inadequate material
If the crack appears on the actual weld = a bad weld (too cold, porosity, contamination ect.)

For example for my 3g and 4g certs you weld 2 pieces of 3/8" mild steel together. After your weld has cooled you grind it flush and bend the plate 180*. The plate is supposed to make the whole bend without cracking anywhere to pass the test.

From the looks of it the weld looks too cold. The link below give you an idea of what I'm talking about. The weld appears to be resting on top of the base material rather than melt into the base metal.

http://www.wcwelding.com/tig-welding.html

Hopefully the waterbox works out better on the 2nd time.

 

[Vumad]

This is more of what I was expecting. They said this time they used rod. I guess the first time they heated the metal but didn't add weld material. I don't think they made the comnection between exhaust and pressure? Going to skip the composite I had planned on and see how this weld goes.

 

[swapmeet]

That looks better.

I concur with the comments about where it broke.

The weld should never come free from the base metal. It should break/ crack/ bend next to the weld because that metal has been heated and 'weakened' in comparison to the weld.

Good luck.