FWIW, there is very little difference in the modulus of
elasticity of the three most commonly available AL alloys:
2024, 6061 & 7075.  Thus, for any given thickness, they're
all going to flex about the same amount.  Moreover, the
fatigue endurance limit for 7075 is only 23Kpsi.  2024, if
you can get it, is a better choice, but it will still need
to be thicker than 1/4", so why pay the higher prices?

Dale R.


> From: "Tracy Crook" <lors01@msn.com>
> Date: 2005/06/22 Wed PM 04:43:30 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: PSRU adapter plate
>
> 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)
>
>