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Old 01-30-2002, 11:12 PM   #1
ImprezedRS
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Default Seam Welding?

What is seam welding, I know they do this to most rally cars and race cars to stiffem the chassis, but what actually is done.
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Old 01-30-2002, 11:23 PM   #2
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Oh thatís easy! Seam welding is where they weld the seams! sorry I couldnít help it..

The way cars are put together is that the various body parts are held together with tack welds. Or that there are lots of spot welds along the seams. When a car is prepped for racing they strip it down to the bare body and re-weld the whole seam. Vola! Seam welding!
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Old 01-30-2002, 11:26 PM   #3
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It's my understanding that the seam is welded for one inch, then a one inch gap is left, then it is welded for another inch and so on.....

Completely welding the entire seam would add lots of unwanted weight.

JD
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Old 01-30-2002, 11:28 PM   #4
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actually i was just thinking about that.. your right it would add alot of weight and probably would also make the weld more prone to cracking.
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Old 01-30-2002, 11:36 PM   #5
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Default Yes they usually skip weld

The pattern of welding you discribe is called skip welding, and yes it is prefered for a couple of reasons.

1. It has essentially the same strength as a full weld with half the welding rod consumed. Weight is an issue, but the welders labor costs money and so do the materials, so it is far more cost effective.

2. If a crack develops in a weld it can only propogate the length of a single weld bead, so especially on high stress items like frames it is safer.

3. On thin material you are less likely to burn through or distort the base metals on skip welds because you are not putting as much heat into the material.

Larry
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Old 01-30-2002, 11:38 PM   #6
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We tig welded most of the seams and it took alot less filler that way. But some said that the it creates too much heat. But we did it anyway. All the seams have to be completely stripped of all the crap that's in some of them. It took along time and we are still finding seams to weld.

Rocky
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Old 01-30-2002, 11:41 PM   #7
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Larry I guess the inevitable follow then is what other types of body prep/welds are there?

Chris
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Old 01-30-2002, 11:55 PM   #8
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Default Thats the most common

Some times you can use what is called a plug weld.

If you can't get to the actual edge of the seam, or you want to spread the load over more of the sheet metal, you can take a grinder or a drill and grind or drill through the top sheet of material and then weld around the perimeter of the hole. Years ago they would sometimes do it with a common stick welder, and start a puddle on the top sheet and just before the arc burnt through both pieces they would quickly pull the electrode away. For all practical purposes it is a spot weld just done in a different way. It works well if you have a wide area of overlap, but you can only get to one side of the seam.

Basically welders are limited only by their imagination. Sometimes you need to be creative to get things connected the way you want.

Also modern cars frequently glue panels together with a mastic adhesive kind of like liquid nails.
Like ILPRocky says to get good welds you have to get all that crap out. Sometimes by placing a plug weld back an inch or so from the edge you can get past the goop that you can't get out.

Larry
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Old 01-31-2002, 12:35 AM   #9
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If you decide to seam weld your car and are going to have a roll cage in it (I assume you will if you're taking the time to seam weld it) consider not doing anything past the strut towers (i.e. boot and bonnet). This creates a less rigid area that is more likely to absorb an impact should you hit a tree. Its crumple zones for drives/passenger safety. The Rubys rally car is done this was to protect the occupants in the event of a collision.

Ryan
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Old 01-31-2002, 08:17 AM   #10
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I think a name more common than "skip" welding is "STITCH" welding.

Additionally, the "PLUG" weld you describe is usually referred to as a "ROSETTE" weld.

--Roy
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Old 01-31-2002, 10:22 AM   #11
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not all rally cars can be seam welded...

Seam welding is not allowed for
SCCA Production class rally cars

J.
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Old 01-31-2002, 12:21 PM   #12
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I was watching a Japanese video where they were prepping a car for racing. I believe it was the JGTC. But they were using the plug weld method on that car.
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Old 01-31-2002, 12:26 PM   #13
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good answers

quick quiz

which production impreza is seam welded at the factory?
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Old 01-31-2002, 12:31 PM   #14
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Current production, or ever? The only one I know of was the 22B.
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Old 01-31-2002, 12:34 PM   #15
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I was gonna guess 22b, but Marquis beat me, so I'll guess type RA...
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Old 01-31-2002, 01:07 PM   #16
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22B it is.

too easy
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Old 01-31-2002, 01:13 PM   #17
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So the next question that begs to be asked... which method did they use? Stitch, rosette, or continuous?
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Old 01-31-2002, 04:57 PM   #18
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well no one uses continuous. I would imagine stitch, if i can be bothered i'll take a look next time i am out in one.
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Old 01-31-2002, 08:46 PM   #19
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Default terminology is always a problem

Lume:

Yup -- I've heard both terms. Like most trades there are both regional differences in terminology and industry differences. Based on your location, did/do you work in the steel industry ? I mostly worked in Large industrial machine shops, and shops that worked on heavy equipment. My dad worked in the trucking industry so a lot of my terminology came from exposure to those industries.

Skip and stitch are both colloquilisms for intermittent fillet welds, which no one but the engineers use

The shops I worked in you'd find different welders that used different terms. I wonder if it is specifically regional, ie east coast, vs west coast or by industry. In the gravel quarry the guys that worked on the heavy equipment almost exclusively used the term skip weld. I never heard the term stitch weld until I went to a smaller machine shop.

There is a subtle difference between the rosette weld and the plug weld though. There is a specific weld symbol for the plug weld in the American Nation Welding Society welding symbols. There is no symbol for the rosette weld. In the description of the usage of the plug weld symbol, it explicitly says not to use it to refer to a fillet weld around the perimeter of a hole (ie a rosette weld).

So as I've seen it used, the plug or slot weld is a small weld that completely fills the hole or slot it is placed in, and the rosette weld is a fillet weld around the inside perimeter of a larger hole.


For those of you who have not worked in the metal trades, here is a link that gives some info on the welding symbols, if your into technical trivia like I am.

http://155.217.58.58/cgi-bin/atdl.dl...237/Ch3.htm#s1

It would be interesting to hear from others about which terms are prefered in which, racing/industrial environment.



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Old 01-31-2002, 09:53 PM   #20
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I'm a stitch welding kinda guy. I also do a great deal of gas or oxy/acet welding. I don't see this method used to much anymore since the advent of TIG. Little known fact is you can weld aluminum with oxy/acet.
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