Chassis Musings...

[islandbloke]

I know that a new chassis for my car will probably run at around

[andydclements]

I would guess the zinc has removed the problem of rust, or reduced it to very low level issue, but I think metal fatigue will be the thing that causes us to replace the chassis on the Esprit.

Some people have already seen cracks / splits apearing and I guess (unlike water causing rust) the only thing you can do to prevent metal fatigue causing cracks is to not drive the car over anything other than a really smooth surface in a straight line, or in reality you can't avoid it.

I have a Europa, with an original lotus chassis, all stressed skin (as the Esprit ones are), I looked at fitting a brand new Spider one, mainly tubular design, instead I found an older spider one, it was strssed skin for most of it, with a tubular section at the front where the rust used to get in the old stressed skin design.

I guess some of the frive for the design change to tubular (can't really call it space frame) design is rust avoidance (less seams- less oportunities for water ingress), and partly added rigidity for the given weight.

Andy

[islandbloke]

Thanks Andy - of course, metal fatigue!

Despite tightening all the chassis/body bolts and renewing all the bushes and shox recently, mine doesn't seem as taut as she once did - maybe that's what was at the back of my mind when I started thinking of this. I imagine the backbone chassis does allow quite a lot of torsional flexing.

Smooth roads would be nice - but I live on the Isle of Man. Where you can drive as fast as you like on most of the roads, but the bumps tend to limit your progress...

The tubular hybrid chassis sounds like a good solution - wonder if Spyder have ever thought of doing one for the Esprit - with cars dating from the 70's I guess the market is growing?

[USAndretti42]

I'm not sure that a tubular chassis would necessarily be better. Of course, that depends on what "better" means to you. It would probably be heavier than a sheet metal structure. It will remove the stress raiser around the gearshift hole but adds one wherever two tubes meet.

The shape of the chassis isn't ideal for maximum torsional stiffness but what changes you can make to the shape are limited by the bodywork you have to sit on top of it.

Mine does not seem as taut as it once was, either. I think it's old age.

Moving on, being galvanized does not mean the chassis is going to be immune from rust for ever. The galvanization provides a sacrificial layer. When it's sacrificed, it's gone leaving the base metal to fend for itself. Over here in California, some builders had the bright idea in the 70's and 80's of plumbing houses with galvanized pipes. If you buy one of these houses nowadays, you budget for replacing the piping because it's a timebomb waiting to spring a leak.

[cbclotus]

Interesting one guys ,i just brush on wax oil and old engine oil over the chassis on my s3 n/a does not look pretty but hope fully protects the chassis ,mot guy i know said she is very good undreneath,mind you he owns a ferriai is it 355 race car ,must admit i never know which model it is when i go to his garage ,rather have my lotus . before that he had a fibre glass 308 nice car ,he also has a detamtso pantera that he wants to sell left hand drive ,sorry if ihave gone off the subject. cheers all .mike s3

[t70]

I wonder if the best possibility is to simply wrap the entire chassis in 2 or 3 layers of carbon fibre... I know this would increase weight, but the stiffness (assuming that you layer the carbon fibre with the correct orientation for torsional rigidity) would be much better. The other thought is to drill massive amounts of holes in the steel chassis and then layer it with carbon fibre... This would probably be the most effective at weight reduction and maintaining the torsional strength.

[islandbloke]

Trouble with that Otis is that you'd need to know something more than I do about carbon fibre ("ermmm, it's black and sexy"), but I take your point.

With many of us running old cars/high milers (Lottie's on 135k), I wonder if Lotus themselves ever considered a 'life' for the Esprit chassis? I know that if I had the space and the spare money, I'd probably buy one for the next time I need any major work doing, and swap it.

Probably after painting the whole thing in POR-15 or something.

[t70]

knowing nothing about carbon fibre shouldn't matter... i don't think it's actually that hard to use... you need a big bag to wrap the chassis in.... a vacuum cleaner to suck the carbonfiber to the surface... and some heat to cure it.... an over-sized blow dryer... you have to align the grain of the carbon fibre in about 5 different directions taking into account the torsional necessities at each location... I'm not suggesting a perfect job... just a little help to the chassis... alternatively... you could take the whole chassis and chrome plate it or something... hehehe... I'm sure it wouldn't be that difficult in the end...

actually... there's one other thing that you can do... never thought of this before... but you could re-heat-treat the whole chassis and then cryogenically freeze it. This process re-aligns the metal molecules better... it takes the carbon content within the steel and basically smashes it into little bits within the steel, then when it is re-heated after freezing the carbon is evenly distributed throughout the steel. This creates a very long lasting metal.