whats the latest on chassis repairs?

[bordseye]

I know that the factory say that a bent chassis cant be repaired, presumably because of the glue and rivet assembly. Maybe because the extruded bits arent available as spares. But I have been told that racers do repair bent chassis substituting welding for glue.

So factory backside covering apart, just how repairable in reality is an Elise / Exige chassis? Note - repair not bodge.

[Hugh Jarse]

Mine is a cat C, with a lower wishbone front rear bracket ripped off and reattached by welding, plus a small tear also welded. Im happy with it. I couldnt tell you about dealloying etc however in my vaguely considerable experience small brackets attached by glue and rivetting (small contact area) wont be weaker welded (assuming the metal is weld friendly). Glueing becomes advantageuos in larger contact patches. Obviously when you are large company like Lotus you cant accept a weld locally a glued chassis, so thats how you fall between two stools and get a cat C. Hopefully other people will chip in to explain which grade of ally is in the chassis, then ill be wiser.

[Jodele]

Lotus had the option of welding the chassis...tried it, tested it and rejected it! The aerospace industry does NOT use welded aluminum structures either. The problem is that the joint can not be heat treated after welding. I would not weld repair this chassis even though the chassis is made from "weldable" aluminum. Bonded aluminum structures are constantly repaired in the aviation industry...so it can be done. The engineering would probably be the most expensive part, but aviation qualified technicians (in England and most of Europe, they are called engineers also, so very confusing) aren't cheap either. The 6000 series aluminum was chosen for its mass produce-ability properties, not for its weld-ability properties or its strength properties. Lotus (and all of the automotive industry) has sacrificed strength for mass produce-ability. Sad, but a fact of life.

Lotus just flat out stated that the chassis is not repairable because the aerospace expertise is just not available in the automotive industry and by the time you've hired the right, qualified people to design and execute a proper repairs on a bonded aluminum structure, you might as well just purchase a new chassis for about the same money...

I am an aerospace structures engineer and design structural repairs on aircraft every day...including bonded aluminum structures.

[bordseye]

Are both the sheet and the extrusions used in the chassis heat treated. If so, how and at what sort of temperature? My working life was in the steel industry so I understand heat treatment as it is used for steel but not for non ferrous.

And what about my F430. That has a welded ally chassis. Presumably from what you say it is a different grade of aluminium. Or maybe just thicker to give strength - it isnt a light car.

last question. I had thought that the Lotus chassis after glueing went into an autoclave to really fully cure the epoxy glue. Is that correct?

[Jodele]

The Ferrari is ALL aluminum and the whole chassis is put into a heat treat oven after welding. The Lotus is BONDED and the glue will be destroyed in a heat treat oven... You can heat treat every individual part but not the whole assembly once bonded.

All of the extrusions are made out of a 6063 aluminum alloy - probably in a -T6511 temper. The pan of the Lotus is made from recycled aluminum... so garbage...