I've been reading bits and pieces about how adhesive technologies are becoming a desirable alternative to welding in some circumstances. In particular, GM apparently glues the seams of the new Camaros in addition to the usual spot welding to get things less flexy. Does anybody know much about this? Would seam gluing be something reasonable to do instead of seam welding, if one wanted to avoid having to do lots of metal prepwork and repainting? I wouldn't expect to match the improvement of proper seam welding, but perhaps there are adhesives reasonably accessible to Joe Average that would make a difference worth persuing?

What new camaros?

Joe UAW Worker with a glue gun: $35/hour
Robotic spot welder: $250,000 + programmers + maintenance crew

Okay, so call me cynical...

Joe UAW Worker with a glue gun: $35/hour
Robotic spot welder: $250,000 + programmers + maintenance crew

Okay, so call me cynical...
Cynical

Cynical

Well, I did ask for it.

Seriously though, the manufacturers use it because it's quick and cheap. IIRC, you can get 3M Panel Adhesive from body shop suppliers. Probably not the same stuff as is used to fill unibody seams though.

I CAN tell you for certain that rally teams go to great lenghts to remove the seam adhesive when prepping a shell for seam-welding. I'd guess that they feel welds are stronger than glue. Or at least easier to diagnose for fatigue.

Cars are spot welded and glued because it's cheaper and does the job for everyday driving. It's more forgiving on various surfaces hiding squeaks and rattles easier.

A rally/race car isn't build for comfort; it's build for speed and handling so seam welding is the way to go.

Welds will last longer than adhesive and you are correct that it's easier to see fatigue w/welds.

Having worked in an automotive assembly plant, an automotive metal stamping plant and now @ a rally shop I've seen both methods. I'd go w/welding personally.

IIRC, Mercedes Benz or some Euro manufacturer was experimenting w/a fully glued unibody a few years ago.


-mykr.

This is where I first saw mention of the new Camaro being seam glued:
http://www.autofieldguide.com/articles/089903.html
I found particularly interesting how the spot welding sort of bolsters up some of the glue's shortfallings, which would be something lost in a fully-glued approach.

I later chanced across a thread on usenet about common rigidity failure modes for older Camaros, and the final post was a musing on whether or not the glue for the new ones would keep things stiff for very long. Sounds like they're sufficiently new for that to remain unknown for a while, though.

Chromer and mykrrr, are you definately talking about structural glue that is intended to be a cheap alternative to seam welding, or merely something to squirt in all the seams to keep out moisture, discourage squeaking and rattling, and possibly even forestall the impact of a failed spot weld?

When I mentioned MBenz, I was talking structural glue.

When I mentioned glue and spot welding, I meant most other cars on the market. That's the way it's done. Not the most secure method but it does the job...

-mykr.

Thats all Lotus uses on the Elise. Pretty sure there's no welding envolved. Not sure if its the same sort of glue but its suppose to save weight.

"Seam gluing" is nothing new. Our 94 Impreza L shell had it...heck, even my 1967 Volvo 122 had it!

Gluing is cheaper, and adequate for street cars, but for stage rally cars, tho, it's not gonna hack it. We seam-welded the L shell more than 2 years ago (stitch welds about 1" apart along all seams we could reach). With probably 20 events on it since then, the shell is still straight (except where we've bent it, of course!) with good panel gaps, great door fit, etc. No doubt the full perimeter tubes on the cage and F/R strut bars help, but you get the idea.

On our 98 GC8 WRX project, we bought the car caged, and it had some seam welding but not enough. After half a dozen events, we found some panel migration--maybe 1/8" around edges of the footwells, for instance. That has since been rectified, and we'll be doing more next winter when the car is stripped for its periodic rebuild.

The panel adhesive is a pain to deal with, as is undercoating. The WRX shell had been extensively stripped of undercoating (by walnut media blasting I think), so it's been fairly easy to update. The L had none of this; where we stitch-welded the shell, the undercoating lifted and there are numerous rust-prone spots to deal with now. I've gone around and wire-brushed these and hit them with POR rust sealer...we'll see how well it lasts.

Cheers, hope this helps.

Dave G
Serial Scooby Thrasher
Last Ditch Racing

Glue wears out after a long time. Seam welding is not used because it is really expensive nd time consuming. Almost all unibody cars are glued.

Yep... The new Lotus Elise chassis is composed of glued aluminum extrusions. The "tub" chassis weighs only 150 lbs!!

Here are some pics... the red stuff is the epoxy.

http://www.roadandtrack.com/assets/image/1072003163729.jpg

http://www.roadandtrack.com/assets/image/1072003163713.jpg

I had a pre-order reservation, but had to put the order on hold due to business and family obligations. I'm hoping to be back on track for a new Elise in a year. Maybe they'll turbo-charge that baby by then??

Mike

BMW in all their wisdom is now using structural glue and rivets to attach the entire aluminum front section to the steel body on the 5 and 6 series.

Using that type of adhesive for seam sealing would probably improve chassis rigidity somewhat, like a poor man's seam welding. I believe Dow Corning makes the glue used for the BMWs. As clyde has said, the seam sealers used by OEMs for a completely different purpose would be worthless for this.

BMW in all their wisdom is now using structural glue and rivets to attach the entire aluminum front section to the steel body on the 5 and 6 series.

Using that type of adhesive for seam sealing would probably improve chassis rigidity somewhat, like a poor man's seam welding. I believe Dow Corning makes the glue used for the BMWs. As clyde has said, the seam sealers used by OEMs for a completely different purpose would be worthless for this.

Structural type rivets (the ones used in aircarft construction) are a good way to connect aluminum with steel from a structural point of view. Glueing it with epoxy will not only further enhance the rigidity but also will act as an insulator between the steel and aluminum, thus minimizing electrolytic corrosion, always a problem when steel and aluminum meet. BMW has got it right.

Structural type rivets (the ones used in aircarft construction) are a good way to connect aluminum with steel from a structural point of view. Glueing it with epoxy will not only further enhance the rigidity but also will act as an insulator between the steel and aluminum, thus minimizing electrolytic corrosion, always a problem when steel and aluminum meet. BMW has got it right.

I've no doubt that's the best way to join the two metals, but I'm just saying from a servicing standpoint it's just not practical for an automotive application. It's a joke to have to remove the dash, motor, complete front suspension, etc (everything on the front of the car, and I mean everything) even for minor front end damage.

Yep... The new Lotus Elise chassis is composed of glued aluminum extrusions. The "tub" chassis weighs only 150 lbs!!

Here are some pics... the red stuff is the epoxy.

http://www.roadandtrack.com/assets/image/1072003163729.jpg

http://www.roadandtrack.com/assets/image/1072003163713.jpg

I had a pre-order reservation, but had to put the order on hold due to business and family obligations. I'm hoping to be back on track for a new Elise in a year. Maybe they'll turbo-charge that baby by then??

Mike
Where can I find more of these pictures?

Thanks,
Dustin

One of the reasons Lotus uses glue on the Elise is probably because aluminum losses alot of its strength from the heat of welding. Most welded aluminum parts are heat treated afterwards which is a bit tricky and time consuming. It would be super difficult if not impossible to heat-treat and age an entire auto chassis and have it come out right. As I recall, most car companies which use joined aluminum for structure go with rivets or glue.

I've no doubt that's the best way to join the two metals, but I'm just saying from a servicing standpoint it's just not practical for an automotive application. It's a joke to have to remove the dash, motor, complete front suspension, etc (everything on the front of the car, and I mean everything) even for minor front end damage.

Since the front end of the Lotus is a single piece fiberglass clam shell any minor front end damage would probably in most every case mean replacing the entire piece. It may not be practical but who in their right mind would buy a Lotus for practicality?

Since the front end of the Lotus is a single piece fiberglass clam shell any minor front end damage would probably in most every case mean replacing the entire piece. It may not be practical but who in their right mind would buy a Lotus for practicality?

I was referring to the new BMW 5, which uses this technology.