New chassis

[elj221c]

There is a reason that the Lotus chassis is a well renowned piece of design ? don?t forget that during the elan production Lotus won six of their seven constructors titles, and are still the 4th most successful F1 constructor. I think they knew a bit about chassis design! (Without a CAD tube in sight!)

Yes, but look what happened when they tried the Elan chassis principles with the Lotus 30.

They didn't get everything right by any means!

[richardcox_lotus]

Hi Chancer

Don't delete this thread - it opens up good debate. I now know more about Triumph Herald chassis' than I did before. It may yet be expanded by those with more knowledge than me !

Rgds
Richard

[ecamiel]

In the 60's, before roll cages, we tested a race Elan chassis. The Elan (and Lotus 30) chassis is great torsionally but was very flexible in the horizontal plane. The body is supposed to make it stiffer but the lightweight body was less effective than the stock body. Ever wonder why the dash is so heavy? It's structural!
Roll cages solve these problems on current race versions.

Eric
64 S1 Hart

[pauljones]

To do full justice to this as a proper chassis to be put into production would take more time and skill than what I have to offer. I have almost finished my project and the finished CAD drawing is suitable for the assessment so im happy.

If anyone can "lend" me a copy of Pro Engineer Id be more than happy to spend a bit of time doing more work on it.

I think I will continue with this as and when, purely to see where the forum guides it.I dont nor did I ever intend to do a full redesign for comercial use,but im happy to play.

The next step will be to take a few measurments of the origonal and my spyder and then apply with a bit of maths to find things like I numbers off each and try to come up with somthing as good or better. I think what makes the lotus chassis good is its light weight.I could come up with somthing as strong,but probably more weight.

My background is in Kitcars so alot of what I know is based on the many problems I have had to over come and looking at other designs and thinking "what if" but as its soon xmas ill do more after. Firstly I need to buy aNRV and sort out my lights.

Happy Xmas all, see you after the break.

Paul

[Jas]

Hi

I know that this isn't an Elan chassis, but just to let you know what it could look like, I show you here what the Europa chassis looks like when done i 3d CAD and exposed to a FEM analysis.

I have been using some of these long cold winter evenings making a 3D CAD model of the Europa chassis and doing some FEM calculations.

I have used the drawings supplied by Eddie Kirby, found on the lotus-europa.com site:
http://www.lotus-europa.com/manuals/mis ... rawing.pdf

I have made some simplifications both because I'm lazy but also because it makes the FEA calculations easier and in some cases possible at all.
Eddie's drawing has a chassis thickness of 1.6 mm, but I seem to remember to have read some were that is was 16 gauge steel, and that would be nearer to 1.5 mm but I have used the 1.6 mm of the drawings.

I have looked at the torsional stiffness by supporting the chassis at the rear damper supports, fixed at one side sliding at the other. Then I applied a load (2.000N) upwards at the left suspension axles and down wards on the right side to give a torsional moment.

This moment gave a chassis flex of ~3 mm at the outer front corner witch translates to 0.45?.
Given the moment of 1.544 Nm this gives us a flex or stiffeners of 3.467 Nm/degree or 2.557 Lb ft/degree in old money.
If the right chassis thickness should have been 1.5 mm then the result will be a little lower.
This should be regarded as a relative figure given the simplifications mentioned earlier, but it can be used for comparing with modifications if one fancies.
One area witch looks like it could be worth strengthening is the chassis leg?s C-profile withs would be stiffer if the ?C? was partially or fully closed of with a sheet of steel, another area could be the transition from the front beam to the square backbone witch could benefit with some gusseting.
The front beam and the backbone looks pretty god, at least for torsional stiffness, but it could be different if we looked at bending, witch I haven't done yet.

I is fun though to compare the result with the figures given in e.g. Karl Ludvigsen's book ?Inside the innovator? where he mentions that the Lotus 24 has a stiffness of about 3.000 Lb ft/degree and the Lotus 30 should have experienced permanently set even before it reached 1.000 Lb ft/degree.

I could be a good exercise to do the same with the Elan chassis, and then compare a standard chassis to one with the AVO/TTR modifications.

[pauljones]

Jannik,

I cant thank you enough, that is fantastic work and something I will aspire to replicate with a standard chassis, a 26r and one of my own theretical designs. But please dont hold your breath. It will be a while. May I ask your expressed permission to use these in my project, due in very soon, with the correct aknowledgements being atributed.
Perhaps you could loan me a copy of you FEA programe?

Paul

[Jas]

Hi Paul

You are very welcome to use it in your project.

The modeling work has been done in Pro/Engineer and the FEM calculations were done in Mechanica which is imbedded in Pro/engineer.
I can?t lend you a copy of the program since it is one we have at work and you need a license to use it. But when I went to college there was always someone who had a ?copy? or you can get a student version at a reduced price, but you probably already know that.

[tract0rman49]

Hi Paul, I have long held the ambition to properly capture the early Elan, Elan +2 and Europa chassis data with a view to providing accurate working drawings to the community.

Can you please do a Pack and go from your ProE files and zip them up. I have my own fully licensed copy of SolidWorks Premium (which includes the embedded Simulation FEA package.) Bear in mind that with todays far more accurate (and readily available) CNC laser cutters and CNC Press Brakes it should be practical to create improved versions of these products. I know there are "Other Options" in this regard but it is my view (backed up by first hand experience of less than acccurate offerings ... i.e. 10mm out on certain critical dimensions), that better solutions should be made available to discerning classic Lotus owners.

Looking forward to your response: Michael Farmer - 1971 Elan Sprint DHC. Elan + 2 Zetec in rtebuild, and son with a 1972 Elan Sprint FHC.

[gus]

cnc anything does not make anything accurate. It is still the guy running the equipment and just as important on a production item, designing the production process. In the chassis, for instance, determining which bend you bend first is more important than how accurate the machine bending it is. And the welding is more important than the bending because you can have a good jig and weld crap into the right shape.

My +2 chassis had a lower suspension pin welded in at least 1/8in out of spec, but hey, that is why they have adjustable toe, right. We cut it out of the crossmember and welded it right, but when that chassis died, I put in a Spyder. It has now been in 6 years longer than the chassis was in it when I bought the car, and at least 10 years longer than when that chassis first needed attention.

I never read this thread, but IIRC the towers on the elan chassis are 16 ga but the structure is mostly 18, and as far as the dash being structural, it may stop a little cowl shake , but the top of it is screwed to decidedly non structural points under the dash pad, so I doubt it lends much. Were it bonded into the base of the windscreen, perhaps.............