[LRRCobradreamer]

D-Cel you asked:

"What is your position on the net affect of the significantly higher tensile strength/lower ductility of the QT housing?
My belief is that it is more resistant to deformation and therefore transfers a larger portion of the total energy into the block mounting points."

My reply:
The short answer is no. The best material selection would be high strength and high ductility. That is one reason why the block bolts material failed in the photos, i.e. low ductility of cast iron. The reason is you want the material to absorb the most energy. Think of it as similar to the crush zone in our modern cars, absorbing the energy of a crash in the least distance.

If I were to design a bell housing, my goal would be to contain all parts within the bell housing. However that may mean the supports, if cast iron, may fail. As long as the casting and the bolts do not become projectiles then that would be acceptable. Holes in walls or injury to people are not acceptable.

I am reminded of an old saying about design. The main issues are to design for performance, reliability and cost. If you only concentrate on two of the three, then it is like designing a three legged stool with two legs. It does not work. I say this because the above are very simplest points to designing a bell housing, many many more issues have to be determined and the company must make money to stay in business also.

D-Cel, that is a good question and thanks for the chance to reply. I hope this helps explain the reasoning why hi strength and ductility are the better material for this application.

Note, where I work we must do containment analysis in case our rotors fail. Think of a 78 lb rotor at 16000 rpm and what could happen.

Jerry, no problem. I did not see anything you said that could possibly bother me. I will not likely be there Thursday, but am going to car show Sunday and likely the one on May 15. Hope to see you soon. Oh yeah, I know that airplane and am very familar with some of the parts, like the IDG.

Lee