JMortensen Posted October 2, 2004 Share Posted October 2, 2004 Please forgive me if this is a totally stupid idea. Wouldn't be the first time. I keep looking at the totally clean and stripped deck inside the hatch and I can easily see where the frame rails are spot welded to the bottom side. It would be VERY EASY to "connect the dots" on those spot welds up on top of the deck. I could turn my welder up just a hair and get very good penetration through to the underside, then I wouldn't have to be under the car struggling to see and reach what I'm trying to weld, and having hot metal popping on the ground right next to my face. Is this a dumb idea? I know that the stitch welding is done on the edge of the frame flange and the spot welds are in the middle of the flange, but it still seems like it would work and would be a lot easier. What do you guys think? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted October 2, 2004 Share Posted October 2, 2004 Jon, Although I'm not on your nomination list, here is a possible method: Using a cutting wheel, carefully cut through the top sheetmetal (floor) exposing the 'framerail' beneath, between the spot welds. Then weld the newly cut slit. That will tie the framerail beneath to the two side of the 'slit' above ensuring that everything is tied together....... Tim Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 2, 2004 Author Share Posted October 2, 2004 Thanks Tim. That idea had occurred to me, but I don't think I want to do that just because I've had much better results welding this thin stuff after I started to close the gap completely before welding. If I made a gap with a cutoff wheel, my welds would no doubt get more bird poopy looking again... EDIT--Oh wait, you meant cut down to the frame rail, then weld back up. Maybe...maybe... Thanks again! Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted October 2, 2004 Share Posted October 2, 2004 The metel man that I learned from used to drill the top layer with a small 5 - 10 mm bit and then weld up the hole. Kind of like a spot weld. You could then grind it pretty smooth and know one would know any better. Douglas Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 2, 2004 Author Share Posted October 2, 2004 Yeah, I would definitely use that method if I were just trying to attach the subframe to the bottom of the car. Stitch welding increases the rigidity of the chassis and is done by welding 1 inch of the frame, then skipping an inch, then welding, then skipping, etc. John Coffey actually has a couple of pictures on his website here (under chassis and suspension): http://www.betamotorsports.com/services/index.html I guess I'm just trying to be lazy, but if it works, then lazy is good! Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted October 4, 2004 Share Posted October 4, 2004 I like Tim's idea (damn, I can't believe I really said that). It will work if you are able to tell when you are through the top layer.. Quote Link to comment Share on other sites More sharing options...
katman Posted October 4, 2004 Share Posted October 4, 2004 Well here's my take on adding welds, stitch or spot, to an otherwise sound unibody. This opinion is based on having prepared and maintained several 240Z's for SCCA ITS racing, several rotisserie restorations, and a few "Texas Sawzall Massacre's" on unibody's that didn't cut it (ha, there's a pun) for racing. The thing I don't like about welding anything extra on a Z that isn't necesary for a repair is that you fry any primer that might have been inside the joint from the factory. Yeah there's a lot to be desired here to begin with, but it if it wasn't rusted before it probably will now. Structurally I'd be surprised if it added any measureable overall stiffness (this opinion based on 20+ years analyzing bolted aircraft structure). Now more welds would reduce the load on the existing spots, and theoretically the flexibility of the joints would be reduced, but I don't think you'd be able to tell the difference in handling. Me thinks this is especially true of stitch welds, which are generally another "half a flange width" away from from where you need them. Now there is some merit in reducing the stresses on the existing spotwelds, so I've been known to add spotwelds via the aforementioned method (I use a 1/4 drill) in critical areas on the race cars. This is usually limited to the frame rails in the vicinity of the sway bar attachment. I see cracks develop on a regular basis forward of the firewall on the frame rails, but never in many years of racing have I seen any signs of fatigue anywhere else on the unibody (suspension parts and stub axles are another matter). Also, having done a few postmortem's on some racing accidents with Z's I can't recall ever seeing something that made me go "hey, a few more spot welds would have been safer". I'm presently wrestling with this issue on my own street car project ('71 with a BMW V12, don't ask- I'm not very far along, my wife keeps spending all my money). Sure is tempting to stitch weld everything in sight while it's on the rotis (actually, what is really tempting is to drill out every spot weld and bond it all back together with a weld thru bonding agent but I told my racing partner to shoot me if he catches me doing that), but in the end I'll probably leave it all as is. Repairs or add-ons is another matter, and I don't disagree with what's already been said. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 4, 2004 Author Share Posted October 4, 2004 Not the response I expected. I've known so many people who have done this to their race car, and it's such a PITA. I have painstakingly picked out a bunch of seam sealer out of several joints, and there was no primer or paint in the joints below the sealer, and in a couple of places there are large gaps with no spot welds whatsoever that I can see (this is on the seam around the bottom of the rear strut tower inside the hatch in particular). It seems to me that you're saying the welds really ought to be in the middle of the flange. I can do that right now very easily. I guess the real question is "Is it worth it?" Quote Link to comment Share on other sites More sharing options...
johnc Posted October 4, 2004 Share Posted October 4, 2004 There's a few different ways of seam welding. 1. Weld the edge of the seam where one panel overlaps another (a lap weld). This is the most common and the easiest to do. Its what I did when I seam welded Henry's 240Z. It has advantages when having to weld seams that have "dum-dum" (seam sealer) in the overlap area. You run a bead just outside the overlap, one over the top edge of the overlap, and then a third down the middle that connects the other two beads. The reason to do that is to get the sealer to burn off without contaminating the final bead the adds the strength. 2. Weld through from the backside of the lap joint (as you state below). I can work but you've got to be sure you get enough penetration and the seam sealer does a good job of keeping that from happening. 3. The third way I know of is the cheater way. You cut a 1/8 to 3/16 wide by 1" long slot through the upper panel down to the lower panel. The run a bead in that slot penetrating the lower panel and overlapping the upper panel. Then grind the bead flush with the upper panel and paint. No way to tell if the car has been seam welded or not. Now, the big question: Is it worth it? Well... it depends. An early 240Z (from 1970 through 1971) does markedly benefit from seam welding. To the point of being able to increase front spring rates by 50 lb. in. In later cars, the benefit drops off. One of the reasons I like to do seam welding is that its kind of an insurance policy. It forces the builder to strip the car down completely and inspect the basic chassis in detail. Its amazing (scary) what you'll find. These cars are 35+ years old and most have been wrecked at least once. Many of the wreck repairs are cosmetic and less then ideal structurally. Also, Hoji at the Nissan factory probably screwed up 1% of the spot welds he did when he built the car and over the past 35+ years, some percentage of the remaing good spot welds have also failed. I just finished seam welding a late 1972 240Z. There were small stress cracks in the chassis where the front frame rails met the firewall, one frame rail had a 1" crack propogating across its width, the driver's seat inside lap belt reinforcing plate was only held onto the chassis by 1 (of its eight) spot welds, and the rail where the front diff crossmember mounted had partially separated from the deck pan above. This was a supposedly only a street car but the beat up center tunnel indicated that this car has lost its driveshaft more then a few times. And, with the car on a rotissierie (sp?) you can seam weld the whole thing in a day. You will need a full 10lb spool of ER70S-6 .023 wire. Quote Link to comment Share on other sites More sharing options...
tube80z Posted October 5, 2004 Share Posted October 5, 2004 There's some good advice from John. I would also recommend that whenever you do this you spray weldthru (3M product) on the area to be welded. This is a very important step in making sure you keep rust away. One good point about seem welding that hasn't been mentioned is that if you ever wreck you car it is much easier to pull the parts back out. If you have simple spot welds they will often pop when you try and do this. I would recommend seam welding on any car the will see a V8 or hard use. Many times the spot welds will not all be holding on our older cars. This helps to ensure that the panels are all glued together. Cary Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 12, 2005 Author Share Posted March 12, 2005 Well I started to clean up the seams, then it got cold. Too cold to be out in the garage. Months passed, and my thumb became stinky. Finally the temperature warmed enough that I went back out to the garage. Here are my first seam welding pics, some are just cleaned up seams, then there's some actual welding. Keep in mind that I have about 3 hours experience welding, including the time it took to do this stuff. I did what John suggested earlier in this thread. On the floor to strut tower seams where there was a big gap I did 3 beads. On on the floor, one on the strut tower, and one to connect the two. Makes the welds big, but getting right in the seam just pulled the dum dum into the weld and made it very bird poopy. One other thing. I do not intend to go with the pubic hair look for my carpet. But I did have carpet installed in this car previously, and the insulation was glued down. So I'm wondering if anyone has any cheater type method for removing the glued down insulation pubic hair looking stuff. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 12, 2005 Author Share Posted March 12, 2005 As far as the frame rails in back go I am going to do them from the top, just haven't started on those yet. I think I'm going to use Tim240z's method and dremel some 1" slots, then fill them in. I think with the power settings I'm using that I might not even need to do that, I could just go slow and let the weld melt thru to the bottom rail, but I'm going to take the extra time to cut the slots in the top just to be extra sure. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 13, 2005 Author Share Posted March 13, 2005 As far as the frame rails in back go I am going to do them from the top, just haven't started on those yet. I think I'm going to use Tim240z's method and dremel some 1" slots, then fill them in. I think with the power settings I'm using that I might not even need to do that, I could just go slow and let the weld melt thru to the bottom rail, but I'm going to take the extra time to cut the slots in the top just to be extra sure.Ouch!!! This was not the way to go. There were spots where grinding the top side and welding from the top worked just as I expected. More often than not it didn't work so good. I would start the weld just fine, then the frame rail on bottom just wouldn't be there (probably because of the curve of the rail and the fact that I wasn't trying to weld the edge of the rail to the floor) so I'd burn through to the bottom rail. I basically just sat there building up the pool so that it got back to the floor level, then continued on. Most of the time this went OK, but there were a few f-ups in there that I'm going to have to patch. Maybe someone with more welding experience could have dealt with these problems a little better, but this was not the best way for me to get this job done. I guess the only saving grace is that now I REALLY know that they're attached pretty well... Quote Link to comment Share on other sites More sharing options...
Moridin Posted March 16, 2005 Share Posted March 16, 2005 ...I see cracks develop on a regular basis forward of the firewall on the frame rails, but never in many years of racing have I seen any signs of fatigue anywhere else on the unibody (suspension parts and stub axles are another matter). Also, having done a few postmortem's on some racing accidents with Z's I can't recall ever seeing something that made me go "hey, a few more spot welds would have been safer"... When I was working on a race team this last summer, I saw a basically new Porsche GT3 RSR start to form stress cracks in the unibody. I think they were going to go through and weld some of the seems up. This was also with a full cage built in, from Porsche. Although, this car was setup to pull over 2.0G's in the corners if I remember right. Quote Link to comment Share on other sites More sharing options...
johnc Posted March 16, 2005 Share Posted March 16, 2005 Jon, As you've learned, the rear frame rails really need to be done from the bottom of the car. Your work looks good and you might have a future in this... I meant to add that I was under a 1971 240Z the other day and saw stress cracks/tears where the rear trans tunnel turned up and met the rear bulkhead. Strange place to see them and I wonder if the car had been in an accident and was badly repaired. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2005 Author Share Posted March 16, 2005 Thanks for the compliment, means a lot coming from a quality fabricator. I need to shoot some more pics from below. The welds clearly went through the whole frame rail as evidenced from underneath, but it was a big PITA. Never again is my new motto. Or at least, never again without a rotisserie. Yeah I think I learned a lot about the car in general as you said I would. The whole rear of the car just isn't put together that well IMO. You've got so many seams and overlaps that it is scary, and once that dum dum comes out then it really becomes apparent that the seams aren't very tight, and it really makes you wonder about the structure of the car. My '70 might be worse than others, but some of my friends have taken to calling it the "Flexy Flier" so it obviously had issues. I've heard you talk a couple times about cars that had issues in the back, I remember once you were thinking that one car had lost the driveshaft, but I think that might be from the front diff mount and strap failing. That happened to a friend of mine and the diff tipped up and beat the snot out of the underside of the car with the rear driveshaft u-joint. Same thing happened to Mark Belrose. Can't say if that relates to your more recent 71 with the stress cracks or not. So far I haven't really found any chassis problems in my tub like torn spot welds or cracks, but I am doing the back, then I'm going to reinstall all the (new) suspension, then I'm going to strip the front and do it, so I still have a LONG way to go, plus I work like a snail which is why I don't wrench professionally anymore... Quote Link to comment Share on other sites More sharing options...
Moridin Posted March 16, 2005 Share Posted March 16, 2005 Check this out for a seam welding. My brother found this on corner-carvers.com website. I actually worked with the guy who is doing all the welding and prep in the pictures, when I traveled around with the ALMS. Might give you some ideas. Here's the link: http://rally.subaru.com/rally/servlet/CarBuilding?part=1&page=1 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2005 Author Share Posted March 16, 2005 WOW... check this one picture out! http://rally.subaru.com/rally/servlet/CarBuildingDetail?part=1&imageId=6 That's a lot of seams. That guy does some BEAUTIFUL work. Thanks for the link. That cage... OMFG... Quote Link to comment Share on other sites More sharing options...
2126 Posted March 17, 2005 Share Posted March 17, 2005 Isn't that a STITCHARU ??? Quote Link to comment Share on other sites More sharing options...
Moridin Posted March 17, 2005 Share Posted March 17, 2005 WOW... check this one picture out! http://rally.subaru.com/rally/servlet/CarBuildingDetail?part=1&imageId=6[/url'] That's a lot of seams. That guy does some BEAUTIFUL work. Thanks for the link. That cage... OMFG... I'm pretty sure that was Sean. He could do just about anything. Mainly, he did carbon fiber repair for the Porsches and did some wrenching. I'm surprised they didn't have him, Sean, do some of the welding on the Porsches. Anyway, that Subaru stuff is crazy. He used to talk about the pit crew support he used to run. Very dirty and very cold. He'd make fun of some of the ALMS mechanics, because they'd complain every once and a while. He just look at them and say "Try doing that in a foot of mud when its 32 F outside." Quote Link to comment Share on other sites More sharing options...
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