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Discussion Starter #1
For the bonded aluminium chassis of the Elise Lotus use an epoxy glue made especially for this application by Ciba Polymere.( Their glues-.some of the are also PU resigns- are sold under the trade name Araldite )

Since many years bonding of aluminium profiles and plates is a very common method in aircraft industry.

Why was it necessary to develop a special epoxy glue for the Elise and which aircraft glue could be used in case you need to repair a damaged Elise chassis ?

For me the ideal repair glue should not need curing in a furnace. Some sunny summer days should be sufficient.

Somebody reading this is working in or for aircraft industry or knows somebody to ask ?
 

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Ruediger,

I suspect Lotus developed a special formulation to support both processing cycles (getting cure in a certain amount of time) and the gaps / tolerances which will exist between elements of the chassis. Special formulations are generally common, and are usually derivatives of a standard compound. Adhesive suppliers are happy to sell you what you want, as long as you buy enough to make it worth their while.

As to standard aerospace adhesives, check out Dexter-Hysol EA9394. It is an extremely strong aluminum filled adhesive, and has very forgiving curing properties. I have seen it used (and used it myself) for very thin structural bondlines (.005 thick) to use as a structural filler an inch thick. The main limitation to thickness in use is strength of the bonded joint (thicker is weaker), and if a large volume of material is mixed together, the adhesive can "exotherm" or get too hot during its curing process. The only thing to not is these adhesives are expensive, they are not like PC-7 you get in home depot. The formulations are not that different, it is more the level of quality control in the material.

I hope that answers the question.

Steve
 

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Discussion Starter #3
Steve

Yes this helps perhaps also in finding another source here in Germany.
Some years ago I repaired a cracked and leaking oil pan in situ (only the oil was drained before)
For this I also used an aluminium filled epoxy resin.( After cleaning with acetone ad grinding the crevice to get something like a V-notch )
I drove the car - it was a Miata- still a long time thereafter without loosing oil again. Only problem was that I am allergic against these resins.
Thank you for the info.

Ruediger
 

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Maybe I don't understand, but this glue is holding the frame together, right? What sort of frame damage do you envision yourself gluing back up?
 

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Discussion Starter #5
Paul

In UK and also here it `s not too difficult to get a damaged frame .
Just imagine you damaged your frame one day and you do not get a new one from Lotus or they charge you round about 8000 $ ----Then -----??? :)
 

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Ruediger said:
Paul

In UK and also here it `s not too difficult to get a damaged frame .
Just imagine you damaged your frame one day and you do not get a new one from Lotus or they charge you round about 8000 $ ----Then -----??? :)
I suppose that I'd wait or pay the $8k. Once Al is bent once its strength drops considerably. The frame is too important not to be able to trust completely.
 

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Discussion Starter #7
Heeeeelp!!!!!!!!

Somebody else may explain to Paul that 2 undamaged parts of a whole when separated properly from the damaged sick or even dead other parts may be recombined to a sound and nearly perfect new whole.

Therefore Paul the surgeons specialised in transplantations would enjoy to get your young and still undamaged heard one day after your smashed your head on some racetrack to glue it into some other person s body who needs it to survive you for some years.:D

But this reminds me to ask here:

How is it possible to separate the sound parts of a bonded aluminium chassis from those which have to be binned because they are bent?

These epoxy resins when treated with liquid nitrogen may be like glass .

How do they do it in aircraft industry where similar tasks certainly are known, too?
 

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Ruediger,

To answer your question, generally bonded parts are separated using heat. Typical epoxies soften at 250 to 350F. However, at temperatures somewhat higher there can be a potential for some loss of strength for stronger alloys (but not much). I had some 6061-T6 which lost 20% after exposure to 600F.



I suspect that the alloys used for the frame not all that strong. The stiffness doesn't change when you bend (plastically deform) aluminum. In aluminum, strength is inversely proportional to ductility, which is important in the formig process. (I haven't seen the technical specification for the hydroformed frame members). I personally would not be worried about doing bonded repairs to the frame - but I am sure it is impractical for an automaker to do this. It takes proper skills and precautions to do this job correctly, and you only get one shot at it. I would not want my corner mechanic doing bonded repairs.

Also, to do these repairs right, it would take $$$ if they are complex. The $8k for a frame is peanuts compared to what a major repair could cost.

Steve
 

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Discussion Starter #9
Steve,

Use of heat to separate the bonded aluminium parts of the Elise chassis may be rather critical too. Aluminium being a very good heat conductor you risk that not only the seam you want to separate is weakened but others too. (There have been fires in the Elise / Exige engine bay – and at least one recall because of these-. After such a fire very similar questions arose )

Therefore I asked whether instead of heat the opposite COLD may be helpful.
( Once I saw a sandblasting equipment using granulated (solid ) CO2 instead of sand in action:
It was able to separate some incrustations and glues from the surface they where sticking on.
And old tyres instead of burning them can be granulated when being dipped into liquid nitrogen before )

But I agree with you that discussing such questions is not worthwhile as long as Lotus is willing and able to supply a spare chassis for a fair price and without undue delay.

If not ? Then dear Elisefans over there open your eyes to see this bonded aluminium chassis under different aspects.

Andere Väter haben auch hübsche Töchter! In the other thread the ATTACK frame was mentioned.

Ruediger
 
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