The error in reasoning here (7075 is twice as strong as 6061 so it can be half as thick) is that the bending strength of a plate is far more influenced by its thickness than by material strength.   This is in addition to the fit problems pointed out by Dean.

 

Just not a good idea.

 

Tracy



> My bellhousing is to heavy. Dave McC is considering buying it for his
> Europa, so I've been researching what it would take to replace it. I
> think Tracy' s adapter plate is a very elegant solution for the
> homebuilder (ie, those of use without a foundry).
>
> His adapter plate uses 1/2" 6061. I've been considering at 7075
> aluminum. It has about twice the cost but also twice the yield
> strength. If I could use 1/4" plate instead of the 1/2", the cost would
> be comparable, but I would have the very large benefit of saving
> something on the order of 4lbs in a very weight sensitive area. I don't
> have the expertise to run the numbers with confidence. All I can do is
> a static analysis following the directions outlined on PL's website,
> just like I did for the engine mount.
>
> Any advise of stuff to look for that might no be so obvious and not show
> up in a static analysis? (the three axis and torsional forces are obvious)