Hi all
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/misc/Lotus%20europa%20chassis%20drawing.pdfI have made some simplifications both because I'm lazy but also because it makes the FEM 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 degrees.
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.
