New adhesives - are they as good/better than welding?

[a310man]

As a new member of the forum, I wil probably ask many quite stupid questions, but as they say, if you don't ask, you don't get.

I had a discussion with my brother recently concerning new 'construction' adhesives. He says that Renault (he's worked for Renault for 35 years) uses adhesives to attach various panels onto their cars using new construction adhesives, including structural parts. It is said that these adhesives are at least as strong as welding. So, as I have a chassis section to repair.....you see where this is going....I have refused to use 'glue' on my chassis.

What does anyone here think? Are new epoxy products good enough? Lotus glued the Elise and all cars since with adhesive.

 

[Leedsutd]

Glue

They are in some cases better than welding, but if repairing then the "glue" only sticks on the surface whereas you get penetration with a weld therefore greater surface area of the bond rather than just the surface which could de-laminate.

 

[Shox Dr]

Cars held together with adhesives are designed to take that into account yours will not have been. While there are special adhesives that can do what you want they are expensive and require very tight adhesion to the instructions, that you will probably not be able to achieve underneath a xxxx yr old car

 

[Wozzaaah]

^ Wot ee says!
If it wasn't designed to be glued together then don't do it.
Non-structural panels are different, I think that's acceptable but anything that forms part of the structure needs to be repaired properly, in most cases, welded.

 

[madkayaker]

I can imagine what your mot tester will say when you take in your car held together with super glue! I bet most modern adhesives will require special kit for curing etc

 

[arthur]

Talking of cars etc I see Honda have just started to weld aluminium to steel!

http://world.honda.com/news/2012/4120906Weld-Together-Steel-Aluminum/index.html

 

[Leedsutd]

alusteel

Hows that work? does the pressure increse the molten temp of the ally?

 

[the snooper]

Talking of cars etc I see Honda have just started to weld aluminium to steel!

http://world.honda.com/news/2012/4120906Weld-Together-Steel-Aluminum/index.html

thats not a new process they have been doing it on expensive yachts for a few years to my knowledge

 

[CRB]

Adhesives have been evolving for years, but I fear it would be unwise to use them in less than optimum conditions.

Seymour Powell designed the frame of the MZ Skorpion to be glued, but it was felt that the lack of mechanical fixing may not inspire confidence. It was 1993 after all. It was diluted after this.

I am sure that some Audi wheels could have been bonded around the same time, but were also riveted due to consumer concerns. Cannot find a picture at present.

Mind you, Audi and MZ were the same company, way back when.

 

[Chickenjohn]

As a new member of the forum, I wil probably ask many quite stupid questions, but as they say, if you don't ask, you don't get.

I had a discussion with my brother recently concerning new 'construction' adhesives. He says that Renault (he's worked for Renault for 35 years) uses adhesives to attach various panels onto their cars using new construction adhesives, including structural parts. It is said that these adhesives are at least as strong as welding. So, as I have a chassis section to repair.....you see where this is going....I have refused to use 'glue' on my chassis.

What does anyone here think? Are new epoxy products good enough? Lotus glued the Elise and all cars since with adhesive.

I don't care what they say, a glue can never be as good as welding.

When you weld you make two pieces of metal into one piece, when you glue, it is still two pieces, but now stuck together with glue. And no glue is as strong as metal.

Modern car methods are bound to come "unstuck" if you know what i mean!

 

[octo0072000]

Hows that work? does the pressure increse the molten temp of the ally?

some alloy tipper lorry's body's have steel floors welded to alloy been doing it a few years now

 

[Chickenjohn]

From speaking to a welding supplier years ago who saw one demonstrated at a trade show, these welders that can "weld steel to aluminium" are really using a special Mig brazing wire that joins steel to Ali, so not really welding.....

 

[Cobs]

Normally joining dissimilar metals is a recipe for corrosion (as in Land Rover alloy panels to steel chassis) however is this just due to moisture between the two - which I assume is not present if they've been welded together?

 

[stormin]

I don't care what they say, a glue can never be as good as welding.

When you weld you make two pieces of metal into one piece, when you glue, it is still two pieces, but now stuck together with glue. And no glue is as strong as metal.

Modern car methods are bound to come "unstuck" if you know what i mean!

Got to disagree there.
A chap at the Northern Off Road Club, had a two wheel drive Cosworth powered buggy. The roll cage / space frame was glued together not welded. It of course had to pass MSA testing to the same standards as a welded cage. He raced it for years without problems.

 

[wrinx]

Normally joining dissimilar metals is a recipe for corrosion (as in Land Rover alloy panels to steel chassis) however is this just due to moisture between the two - which I assume is not present if they've been welded together?

My thoughts too....galvanic corrosion will be rampant, but I guess if it's protected properly it'll last.

Can't help wondering though...

wrinx

 

[TechnicAl]

Hows that work? does the pressure increse the molten temp of the ally?

Its Friction that generates the heat. You can doing by rubbing them together, very fast of course.
In this instance they use a tool to stir the joint. Its a bit like a router bit.

 

[TechnicAl]

Back on ahesives.

A few years ago 3M gave me 2 pieces of Ally glued together. I put it in a tensile testing machine. The aluminium broke before the joint. Oonly problem was that the joint had to be overlapped.

They have been gluing aircraft wings for donkeys years

 

[hotrodder]

I don't care what they say, a glue can never be as good as welding.

When you weld you make two pieces of metal into one piece, when you glue, it is still two pieces, but now stuck together with glue. And no glue is as strong as metal.

Modern car methods are bound to come "unstuck" if you know what i mean!

Gotta disagree there too. Lots of glued materials that offer better strength to weight and stiffness to weight ratios than welded metal. Lotus Elise versus the Renault Spider for example... the Elise is glued ally, the Spider welded ally and because welded joints can't take full advantage of complex extrusions the Elise chassis is 15kg lighter while being 1000 Nm/degree stiffer

Lotus used (posh) rivets too because one weakness of adhesives is peel. IIRC they're on the record as saying that the chassis worked without the ejot fasteners or without the glue- both were used as they complimented each other, covering the others weaknesses

As said the problem with glues for the likes of us lot is the cost of the right ones, the environment that's needed to use them and of course repairing damage/modifying things. Design approach is also very different as welded joints are very different to glued joints

 

[BoatBuilderDave]

Glues are Different.

Don't imagine that they are suddenly an Easier alternative.

They require different joint design. Surface area of joints is important. As is the type of stress. Some glues don't live with shearing forces, others can't cope with peeling forces.
Some can creep under constant loading.

Special preparation and cleaning will be required. Many glues are 2 part, and some require very precise measuring, proper mixing, and many require specific ranges of curing temperature.

Some glues don't live with heat, most epoxies are useless at any sort of high temperature.

Once you start to learn about welding, you realise there is more to it than meets the eye. Adhesives are much the same.

 

[Chickenjohn]

Got to disagree there.
A chap at the Northern Off Road Club, had a two wheel drive Cosworth powered buggy. The roll cage / space frame was glued together not welded. It of course had to pass MSA testing to the same standards as a welded cage. He raced it for years without problems.

Doesn't mean that gluing is better/ stronger than welding. Just means that on this case the roll cage met the standards and the chap had no problems.

Likewise Lotus versus Renault which is not a fair comparison as Lotus have been making composite and fibreglass cars with gluing for years. I still don't accept that a glue joint can be better, stronger than a welded joint.