I have been reading some of these emails with interest from an engineer stand point and find that flight testing is laborious way to test.
Why not simply test the cranks in a physical lab where gradual eccentric dynamic loads can be placed on the shafts and record loaded failure? Some fan shafts geometries have critical harmonic RPM's that will cause failure if the shaft rotates at that RPM for extended time periods. The solution is to stay out of this RPM range i.e. above or below. I think the problem may be fatigue failure due to critical harmonic loading caused by the prop. This would require solids modeling the shaft and stress analyzing. When I worked for John Deere I learned that Deere folks stress relieved all rotating parts in their engines after each machining operation and nitrating all bearing assemblies. The process was similar to the one explained at this web site. http://www.440source.com/crankshafts.htm Ronald R. Eason Sr. President / CEO Ph: 816-468-4091 Fax: 816-468-5465 http://www.jrl-engineering.com Our Attitude Makes The Difference! -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Colin Rainey Sent: Tuesday, January 17, 2006 8:46 AM To: [email protected] Subject: KR> Corvair info post Glenda and Oscar I do not want to sound out of line, and I am obviously not privy to all the information gathered at the testing site. However, I find it alittle pre-mature to declare all non-nitrided cranks as having a problem simply because the only example of that did not have a crack in it. Bill Clapp's did not either, but WW's language was such that he was going to examine it until he found one. The test appears from a distance to be more of an attempt to support the need for nitriding, then to prove that it is truly necessary. Personally, before I go to the trouble to teardown my engine, I would want to see several more examples of cranks run for similar times like Bill's and have no damage, while more of the cranks without showing signs. To draw the conclusion that nitriding will correct the cracking tendency at this point is premature. IMHO for it to be scientific, the test should have been performed with (5) 2700cc cranks nitrided examined, and (5) 2700cc cranks w/o nitriding examined for similar use engines and those results compared. The 3100cc engine is a throw away invalid, because rods and psitons are different which contaminate the accuracy of the information. I have nothing against safety or being cautious, but drawing conclusions this way only means the possibility of unnecessary work being done on engines, and the real problem may not have been found. I do not deny the importance of the testing, but feel the results lack credibility at this time to draw the conclusions that they have. More factors must be considered in order to properly prevent this from occurring with other engines. >From the (4) 2700cc engines, 50% cracked and 50% did not. Why? What was the same about them, and what was different? How were they used differently or the same? What was the fuel type used, base timing settings, carbs, props, compression ratio? How were the 2 engines used that did not crack vs. the 2 that did suffer cracks? We could all change out our cranks for billet steel racing cranks and still develop cracks in them if the true cause of the cracks is not determined. Until you establish the control group correctly, you are just guessing.... Colin Rainey First National Mortgage Sources Lending Solutions in All 50 States 386-673-6814 office 407-739-0834 cell [email protected] _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to [email protected] please see other KRnet info at http://www.krnet.org/info.html
