Lotus Elan

Torsional rigidity of the Elan Chassis

PostPost by: MarkDa » Sat Apr 18, 2020 10:37 pm

Yes - of course I know that for a given mass torsional resistance increases as the material is spread out in a ring reaching a peak at an optimum diameter/thickness.
That's why we have hollow prop shafts and torque tubes.
It's also the reason why space frames chassis have skins riveted on to increase stiffness.

I'm not convinced that Stephenson's bridge was particularly a torsion tube ‐ they each carried a single rail track so the load was central with no nominal eccentricity.
Indeed when you look at Fairbarn's finished design you see very 'heavy' top and bottom cellular sub-structures with 'thin' side skins making it a box girder.
Apparently Stephenson's original 'tube' design was over-stressed in compression in the upper flange.

Britannia_Bridge_wrought_iron_section.jpg
Brittania Bridge Box Section
Britannia_Bridge_wrought_iron_section.jpg (39.37 KiB) Viewed 247 times
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PostPost by: vincereynard » Sun Apr 19, 2020 7:46 am

Frogelan wrote:The Elan interpretation was designed in one weekend by CC in 1960,and when the prototype was made, it showed enormous potential.
Andrew


I'm sure I read that Hickman originally designed the chassis simply to test the suspension layout. Chapman
saw it's potential (cheap) as a way to get over the difficulties he was having with the Elan not being able to be made a monocoque (like the Elite) and a convertible. CC grabbing the credit sounds par for the course!
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PostPost by: Mazzini » Sun Apr 19, 2020 7:51 am

vincereynard wrote:
Frogelan wrote:The Elan interpretation was designed in one weekend by CC in 1960,and when the prototype was made, it showed enormous potential.
Andrew


I'm sure I read that Hickman originally designed the chassis simply to test the suspension layout. Chapman
saw it's potential (cheap) as a way to get over the difficulties he was having with the Elan not being able to be made a monocoque (like the Elite) and a convertible. CC grabbing the credit sounds par for the course!


After the Elite I don't think Chapman had much interest in road cars. Over the years Chapman's devotees may have accredited the chassis to him. Perhaps he was the man with big ideas and others worked out the 'details'. I don't know, just ideas.
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