No weld fusion on frame welds?

[James in Dallas]

I noticed on a recent Youtube video where this Tavarish fellow had picked up a wrecked SL-C that one or more of the frame welds had popped and it was clear that the two bars had not been fused together, just weld piled atop them.

Getting good fusion is welding 101 for a professional welder, and without it, the frame would come apart in tatters in any major collision. If welded properly, the weld itself will not break before the metal around it does (like in this video here where the metal itself snaps before the weld does -

).

Anyone that's professionally welding automotive frames should be able to easily do the bare minimum to make a structurally sound weld, and the fact that it wasn't in this case means there's good potential for a driver to be fatally injured where they might otherwise survive.

I'm hoping there's a good explanation

 

[Dusty]

Im not loosing much sleep over that pic. As a whole this SLC chassis is very sound. The passenger compartment is especially so. If that was a steel weld Id be a little more interested but not for an isolated aluminum weld failure. Especially since the weld is where a thin tube of aluminum is welded to a solid chunk of aluminum.

 

[Terry Oxandale]

I don't have a dog in this one, but why would it matter the material? Wouldn't any failed chassis weld be a concern? Granted, there was some unusual energy (impact) put onto this, but this is a pretty clean break. Perhaps the photo from a different anglel would show some distortion prior to failure?

 

[James in Dallas]

I don't have a dog in this one, but why would it matter the material? Wouldn't any failed chassis weld be a concern? Granted, there was some unusual energy (impact) put onto this, but this is a pretty clean break. Perhaps the photo from a different anglel would show some distortion prior to failure?

The material doesn't matter too much in the sense that fusion is fusion is fusion. Either the two pieces are fused together or they're not. If you're running too cold - e.g., your welder isn't putting out enough energy to melt the two pieces together, or if you're moving too fast - the slower you move, the more heat you put into a single spot on the length of the weld - you get stuff like this.

The problem is that a frame weld is a structural weld, and structural failure on a vehicle has the potential to be catastrophic (see any video of a race car disintegrating after a collision).

If the person welding a frame is either unskilled or uncaring enough to fail to do the weld correctly and safely, then the question becomes "What percentage of all the other frame welds are like this?". If you don't spend a lot of time doing aluminum welding, you probably won't be able to determine that by just a visual inspection. Especially if they've cleaned the welds up afterwards. You can get the welds x-ray inspected, but then you'd have to take literally everything off the frame and it wouldn't be cheap.

The thing is, as a professional welder, if you're working on structural stuff in a professional, paid capacity, you should have a welding cert. Usually more than one. If you have one, you know when you've achieved fusion on a weld or not. Beginner stuff for a professional. So if your welds don't have fusion and you know people will be trusting their lives to your work, you're a pretty scummy individual.

The other scenario is that the welder was new, self taught and knew how to make a pretty looking weld, but not a structurally sound one. This happens a lot, but any shop foreman would never hire a person like that to work on structural stuff. Most jobs would ask you to come in and do a test before getting hired and they'd examine the resulting work. People fail those tests all the time because they exaggerate their experience. At a good shop, those people do not get hired.

In the end, the result is the same. You get welds that look nice, but your frame falls apart in a collision. Some of it? All of it? Who knows? Who wants to take that risk?

 

[Adam]

The weld of an aluminum joint is weaker than the base material which is converse to most steel applications. The welds on the RCR chassis are not cold welds. Not on my chassis or any that I’ve seen. One could argue the joint construction can be different but impact integrity is much a different simulation than rigidity. I’m an engineer at Lincoln electric so welding is our thing. If anyone ever needs info, let me know.

 

[James in Dallas]

The weld of an aluminum joint is weaker than the base material which is converse to most steel applications. The welds on the RCR chassis are not cold welds. Not on my chassis or any that I’ve seen. One could argue the joint construction can be different but impact integrity is much a different simulation than rigidity. I’m an engineer at Lincoln electric so welding is our thing. If anyone ever needs info, let me know.

Why does there appear to be no fusion though?

 

[Adam]

Why does there appear to be no fusion though?

Can’t see to the root of the weld but it looks like a tensile fracture. The base materials proved stronger than the weld itself. I imagine that area could have been prepped better to accept a deeper penetration weld. Maybe secondary brackets to hedge their bets in the event of high g impact. We have specifications in design that say a weld joint cannot fail on critical areas during destructive testing.

 

[James in Dallas]

Can’t see to the root of the weld but it looks like a tensile fracture. The base materials proved stronger than the weld itself. I imagine that area could have been prepped better to accept a deeper penetration weld. Maybe secondary brackets to hedge their bets in the event of high g impact. We have specifications in design that say a weld joint cannot fail on critical areas during destructive testing.

Yeah, I noticed the edges of the material weren't chamfered.

Anyway, it doesn't look great.

 

[Dusty]

Are there more pics of the rest of the chassis? What Forces led to the damage? How does the passenger compartment look? The Slc is particularly appealing to me because it looks like one of the safer kit car chassis out there.

I have raced and wrecked in desert races, rally races, and rock races. It’s one thing if the chassis fails and causes a wreck. It is a totally different matter if you wreck and the chassis then fails in places that don’t keep you alive. Has anyone experienced or know of cases where the Slc Chassis has failed during normal driving or even Racing applications?

Several years ago me and my little brother were racing the Prescott rally in Arizona. I was navigating in the dark and in the rain and I wasn’t doing a very good job. I could not convince my little brother to slow down as we were making good time. My brother lost control of the car and it launched over a fairly steep Embankment. For several horrifying seconds and over 100 yards we plowed through sage brush and launched over several ice chest sized rocks before coming to a violent halt against a huge boulder. much of the suspension and body were destroyed, the Saginaw box was torn from the frame, and two of the tires were blown but the seats stayed secure, the harnesses held tight, the neck braces worked, and the passenger compartment was not compromised. All that mattered then was that we walked away.

We were so far down that deep gorge that the rest of the race totally passed us by in the dark. And the best part of the whole story is that it wasn’t even our car.

 

[Frank Clark]

I'll throw my 2 cents in here, but take it for what it is...

With aluminum, keep in mind most of these 'raw' materials are heat treated. But the chassis is not heat treated after the welding. So the weld and the HAZ area around it are basically T0 while the material is likely T6. For that reason, you can expect the failure to be in the bead or in the HAZ. So the fact that the weld came apart is not necessarily an indicator of a problem.

However, if that was my weld, I'd be asking myself how I managed to get a thin section of tubing welded to a piece of billet without making any significant penetration into the tubing.

I expect, if you cut farther into the tubing you would find that the tubing back 1/8" of an inch from the edge is penetrated and that the edge of the tubing was cold. My *best guess* is that the welder concentrated heat on the billet then walked the heat over into the tubing and bridged those two areas without getting any real penetration on the edge.

But like I said, that is my best guess. I would like to see a cross section cut into that tubing.

I would be willing to bet that the tubing to tubing and the sheet to sheet welds do not look like this. With Aluminum, welding a solid billet to tubing takes a lot of care to not destroy the tubing.

I would not loose any sleep over the soundness of your tub. In a significant wreck, you ARE going to damage the chassis from the firewall back.

With our Sprint Cars, we pretzel-ed one chassis every 5 races this year - and those are US made 4130 steel. Even managed to snap the front off an iron block engine. There is lots of energy in a crash. It's going to go somewhere.

 

[Howard Jones]

Here's a thought. If you backed a SLC into a wall hard enough to bend that 2X2 solid upright chassis member, something will have to give. The question is what do you want it to be? I vote for the square section of chassis (the piece that the suspension components are mounted to). This saves the forward section, the part that has the engine in it, and (hopefully) makes the repair much simpler.

The video shows that the tub has taken some energy into the passenger side front corner so I would be guessing that it went into the wall? and then slapped the side of the car at the rear pretty hard or spun and impacted again. In any case it hurt the rear also.

I will say that the passenger area is pretty solidly intact. I had always speculated that it would take a very hard hit to get hurt as a result of the chassis cockpit cell folding up.

I won't comment on the welding (lack of qualification) and if I have previously then I shouldn't have but I think Frank is on to something in the above post.

SLC Video on Tavarish

Has anyone seen this youtube channel? It will be interesting to see how this build turns out!

www.gt40s.com

 

[AJ Newman]

I actually have the chassis now, if anyone would like some more in-depth pictures of the damaged areas.

I own a manufacturing/fabrication facility with full capabilities to fix and repair the chassis. The entire rear frame section will end up being cut off the car, waterjet jigged onto a fixture table and then welded back into place on my fixture table.

One more note on another weld failure. When I started stripping the car, about 12” or so of the top of the gas tank was completely cracked down the center of the weld of the fuel cell. Fixable yes, but that scares me more than the rear chassis damage.

The front tub definitely took a hit on the pass side front area, all the welded areas seem to have stayed intact at this portion. It just caved the vertical section somewhat where the arms mount to the tub area.

-AJ

 

[Frank Clark]

12” or so of the top of the gas tank was completely cracked down the center of the weld of the fuel cell.

It seems I remember 1 or 2 guys before that had cracks in the tank welds (not on wrecked cars). I was thinking those were early cars. Anyone remember any details?

I assume the tank did not take a hard hit. *Seems* that would more than likely be because of a poor choice of filler for the tank material.

I switched to Hobart's 4943 filler for most things that don't need ultimate strength. That solved a lot of problems (but puts a dent in the wallet).

AJ, I am thinking some early cars had tank cracking issues, but it's been years so don't bet the farm on that. If I had that kind or crack, I'd assume the welds all the way around the tank are suspect and I'd build a new one. I would put in a sump, add some baffles, extend the tank full width of the chassis, put the pump(s) in the tank and use hydramat for the pickup. Just my 2 cents worth.