Continuous bead??????

[Cuzz]

Hey guys, it's me again. I've been lurking and reading all the posts for metal fab while I'm aiting for my floor pans to come. Lo and behold while I was talking to someone they made a statement that brought me up short, thus leading to this question. Is it safe to make a continuous weld bead on the center portion of both floor pans, or should you leave a few places open? The person I was talking to said that doing a full bead was dangerous because in a crash there is no place for the metal to "give". Man, this is getting more complicated as each day passes. Any help from you guys, as always, is appeciated.

Steve

P.S. I don't know if anyone else knows this or not, but it was new to me and I thought it was really cool so I thought I would pass it along. If you need to brace your car for welding did you know you cold use the metal frame from an old bed? I never thought of that! See I told you I 'm new to this!!

[NickP]

Hey guys, it's me again. I've been lurking and reading all the posts for metal fab while I'm aiting for my floor pans to come. Lo and behold while I was talking to someone they made a statement that brought me up short, thus leading to this question. Is it safe to make a continuous weld bead on the center portion of both floor pans, or should you leave a few places open? The person I was talking to said that doing a full bead was dangerous because in a crash there is no place for the metal to "give". Man, this is getting more complicated as each day passes. Any help from you guys, as always, is appeciated.

Steve

P.S. I don't know if anyone else knows this or not, but it was new to me and I thought it was really cool so I thought I would pass it along. If you need to brace your car for welding did you know you cold use the metal frame from an old bed? I never thought of that! See I told you I 'm new to this!!

Steve I can’t agree with this statement without some kind of test data to back it up. What I would submit here is to look at Laszlo’s site, http://www.picturetrail.com/gallery/view?p=999&gid=4009142&uid=465705 (http://www.picturetrail.com/gallery/view?p=999&gid=4009142&uid=465705) AKA Chevynut, and see his process for the floors and welding methods used. There are several others here and over at CT that have done great things in the floor area and are worth your time to study. Look at Robert’s (AKA MP&C) http://s5.photobucket.com/albums/y167/rmccartney/? (http://s5.photobucket.com/albums/y167/rmccartney/?) too, he also has done some fine work.

[MP&C]

Steve, did he indicate where the welds should be left open? What if this supposed open area were in the wrong place and the give allows an object intrusion right into the passenger? I would think any give should be outside the passsenger compartment to absorb energy before it gets to the passenger compartment, to protect the passengers. I'm not sure this was as much an issue then as it is today, especially considering that collapsible steering columns came after 55-57. But I'm quite certain that if you hit anything hard enough, continuously welded or not, something's gonna give.

[Rick_L]

I think the person who gave you the advice was confused.

Generally you don't weld thin sheet metal continuously - as in pulling the mig gun trigger and "letting it rip". But the reason is not structural. If you weld continuously, the sheet metal will get hot and eventually a hole will burn through. A better technique is to tack weld every few inches - then come back and tack weld halfway between each initial weld, then come back and do it halfway between, etc. You can actually end up with a "continuous" bead with this technique. Or, you can use a pulsing technique to do the same thing. I find the pulsing technique useful and faster than multiple tacks.

Sometimes a continuous bead is not necessary for strength. "Skip welding" is often used in industry. If you skip weld, you will have to do something between the welds to seal the joint, if you want it sealed.

But there's no reason to think that a continuous weld makes for an unsound or incorrect structure.

[Cuzz]

Nick, I gotta tell ya those two sites you recommended already have a special place on my garage wall!!! That was the reason for my confusion, this person was a respected body technician and some one I've known for quite a while. It could be that I misunderstood where exactly they were referring to because the conversation was skipping all over the car. I just needed to check with my security blanket (you guys:D ) to make sure I was going to do it right. I had planned on following Roberts post when the floor pans and braces come in as his is the best way (well maybe not the best:) but the only way I've seen) to replace the floors and rockers.

Again guys, thanks for reassuring me on this critical area!

Steve

[Nutjob]

Even modern cars are designed such that the passenger cabin is rigid. The front and rear of the vehicle are designed to work something like an accordion to absorb the shock of impact. It's also worth noting that the factory floors in these cars are 1-piece though the front and rear are rigid enough to transfer most/all of the impact shock directly to the passenger cabin. A full-length frame will do that :)

[Shua57]

I would recommend that you don't crash..:D I agree with the rest of the comments. The only reason I would not do a full bead is when you are welding body panels and are concerned with warpage. Under that circumstance I would do a 3/4" weld/spacing weld. I think I may be confused. Is it a continuous bead or a full bead? A continuous bead will do what Rick said and will overheat the metal and burn holes (cranking the welder on and burning without stopping). A full bead is a weld down the full length of the seam which is appropriate. So, if he said a continuous bead then he is right. The metal is just too thin.

[Cuzz]

From what I gathered from the conversation I could swear it was meant as a full weld because it was said not to weld in one area to long.

Steve

[Shua57]

You ever been in a car that had rusty floor boards? The flex like mad because there is no tension strength. They feel spongie, like they are moving (which they are). I would weld the things as solid as I could. Voids in the welds would cause cracking in the welds from all the vibration and they become weak and they can hold moisture and rust...JMHO

[Chevynut]

The original floors didn't have a seam in the center. So what could be wrong with a weld bead?

[L&L CUSTOM PERFORMANCE]

EVIDENTLY THIS BODY MAN WAS TALKING INREGARDS TO CURRENT UNIBODY CONSTRUCTION. WITHOUT GETTING LONG WINDED THE UNIBODY HAS CRUSH ZONES BUILT INTO IT AND IT IS NOW RECOMENDED THAT FLOOR AND STRUCTURAL COMPONENTS ARE REPLACE AT THE FACTORY SEAMS AND USEING A SPOT WELDER TO DO SO. MIG WELDING ,ESPESCALY IN AREA'S MADE WITH HIGH STRENGTH STEEL IS NOT RECOMENDED ON LESS YOUR USEING A PLUS MIG UNIT . AND SINCE THOSE GO FOR 4 TO 6 THOUSAND DOLLARS. I DON'T THINK TO MANY OF YOU HAVE ONE. BUT GETTING BACK TO THE TRI FIVES, THE STRUCRUAL STRENGTH AND CRASHABILITY OF THE FLOOR PAN IS NOT A REAL CONCERN . IT IS THAT BIG STEEL FRAME THAT IS NOT GOING TO GIVE UNDERNEATH. IF YOU CRASH THIS THING THAT HARD YOUR IN BIG TROUBLE:eek: :eek: . I WOULD BE MORE CONCERNED ABOUT A SKIP WELDED FLOOR PAN COMEING APART ON IMPACT AND ENTERING THE INTERIOR COMPARTMENT. I WOULD WELD IT SOLID IN THE CENTER AND BUTTON WELD IT TO THE BRACES AND SEAMS JUST AS YOU WOULD WITH A SPOT WELDER AT THE FACTORY. GOOD LUCK LARRY www.llcustomperformance.com

[chevman57]

And if you left places unwelded in the floor boards it could create a place for exhaust gases to get into the passenger compartment, which wouldn`t be safe at all.
Terry

[Rick_L]

L&L, good comments. Unibody structures and 55-57s are pretty far apart.

Educate me, what's a "plus mig"?

I'm not a student of unibody collision repair - but what I've seen is that mig welding is generally not allowed on high strength low alloy steel structures that are common. I'm also assuming they frown on butt welding, wanting an entire brace or panel replaced with a collision repair part. And they just say don't rather than trying to specify how to do it correctly, with proper joint design and all that.

The floor in a 55-57 is NOT a structural part of the car per se, and is made of low alloy steel that is readily weldable and can be repaired by just about any means out there.

[L&L CUSTOM PERFORMANCE]

SORRY MIS SPELLED. A PULSE MIG ACTUALY CONTROL'S THE HEAT INDUCE INTO THE WELD AT A CONSTANT TEMPETURE. A CONVENTUAL MIG THE INITIAL HEAT IN PUT IS VERY HIGH AND THEN LEVEL'S OFF AS YOU CONTINUE THE BEAD. A PULSE MIG DEVELOPE'S AN EVEN HEAT PENATRATION THROUGH OUT THE WELD CYCLE. LEST CHANCE OF HEAT EMBRITLEMENT IN WORKING WITH HIGH STRENGTH STEEL. COMMONLY FOUND IN TODAYS AUTO'S. NOT A VERY HIGH TECH DISCRIPTION BUT THAT'S THE BASIC'S AS I UNDERSTAND THEM. LATER LARRY www.llcustomperformance.com