[Ant]

Thanks for the replies,

I spoke to the certifier today and he has asked me to supply information on the Rectangular front lower suspension arms 40mm x 25.40 x 2mm WT, these arms have been used for the best part of 25 years on cars the same as mine that ran in the Cobra Bardhal series early 1990's in France. We have a Hobby manual with minimum sizing and we are able to build aslong as the material selected meets the minimum standard, what I am wondering is why are the asking me to come up with a yield analysis of the rectangle steel when I am paying them to do a job and they must have some basis or knowledge to approve or reject a submission.

One option might be as I did with my single hoop roll bar I had to spend considerable money etc with a consultant Engineer.

Vector1 1.25" appears to be a good diameter for a lower wishbone for an approx 950kg cobra like mine, I guess your arms would be 2mm wall thickness minimum.