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Aerolitellc(at)aol.com
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 Posted: Tue Jan 29, 2008 1:33 am Post subject: Clarification of the Ocala crank replacement |
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In the interest of the Corvair aircraft engine community and the integrity of the information on this list I need to clarify “case three” of the WW crank update, Part #1.
I, too, am very concerned with the most serious challenge facing the Corvair engine, crankshaft breakage. This problem has led me to investigate better ways to improve the crankshaft’s durability through improved preparation and nitriding as well as possible sources of new crankshafts incorporating changes to reduce the transmission of prop forces.
The circumstances of “case three” follow.
The very first attempt to start the engine resulted in the cylinders firing totally out of sequence because of a misinterpretation of the spark plug wiring as described in the green Corvair Chassis Shop Manual. My second attempt that same day was even more disastrous, with a large backfire occurring through the intake. It was at this time that damage occurred to the engine. Spark plug wiring resolved, the engine fired smoothly but was exhibiting blow by. A compression check showed the #2 cylinder with very little compression, and upon further examination, a crushed ring was found. Replacement of the rings of #2 cylinder was attempted, but a crushed skirt on the piston made the entire piston replacement necessary.
It is obvious to me that the violent counteracting forces the engine experienced at this time started the crack in the crankshaft, and possibly the beginning of the crack in the case as well. Mr. Bradner’s aircraft functioned smoothly until he began to notice a vibration on a trip between his home in Ohio and his Florida residence. The trip encountered bad weather and terminated in Ocala when the vibration became very pronounced. It is probable that the breakage occurred at WOT on takeoff from his prior stop for fuel, Waycross, GA. Ben contacted me upon landing in Ocala and after our discussion, I drove down from Louisville, KY, to Ocala where the plane was temporarily hangared with enough parts to build another engine while Ben continued his return to his Florida residence by car. Inspection of the engine showed oil leakage and prop movement. Complete disassembly of the engine revealed the broken crank and a hole in the case above the #6 cylinder. I have pictures of the case and crank and have been promised return of the crank by Mr. Wynne after a complete examination and analysis by Embry-Riddle. I retained the broken case. Careful inspection of all pistons by Mr. Wynne and me revealed no signs of on-going detonation, and the only parts of the engine requiring replacement were the broken crankshaft and the engine case. The obvious misunderstanding regarding timing marks was because I use a digital timing light which only uses the ‘0’ degree TDC mark as all other settings are electronically adjusted for within the timing light allowing it to use only the ‘0’ degree mark. This engine did not operate outside of the timing that William Wynne’s Engine manual states and was built completely with parts from William Wynne and his designated suppliers.
The bottom line is that this crank failure cannot be attributed to unusual engine timings but to its initial startup with incorrect engine firing sequence and therefore should not be counted as a crankshaft failure, at least not a normal or unexplained crankshaft breakage. The crankshaft damage started with the abnormal forces it experienced at the time of the #2 piston damage that caused its replacement.
It does, however, accentuate the need for crank examination when a problem of this nature or a prop strike is experienced.
Mr. Bradner had flown his 601 for approximately 105 hours before his landing at Ocala and has flown an additional 50 hours since the replacement of the crank and engine case. I think that he should be commended for his recognition of the vibration and the subsequent abrupt ending of his flight plan to Bradenton. It would seem to me he demonstrated the same good judgment that Chris did in case #2, and his flight was not just for pleasure or for performance checks, but had a specific destination /time schedule need that he over rode to investigate the vibration experienced after takeoff from Waycross, GA..
As a matter of record, the only personnel contacted for advice/consultation during the build were William Wynne’s trusted mechanic and test pilot, Gus, and our supplier of reworked heads. I did not, do not, use engine advice from unknowledgeable, unproven individuals where the Corvair engine is concerned, and I have flown in Mr. Bradner’s Corvair powered 601 as well as 0-235 powered 601s, and quite frankly, prefer the smoothness of the Corvair and its lighter weight/better weight distribution within the 601 airframe..
As a result of the crank problem, I have learned that the haste I exhibited and the pressures I felt trying to make up for a two month delay caused by Fire Wall Forward parts unavailability caused costly mistakes, and that my delivery commitment to a customer can not be allowed to affect work quality. I intend to always have spare parts/engines available in any future endeavors to remedy any unexpected difficulties I might encounter.
I hope this answers any questions regarding this specific broken crank incident and satisfies my obligation to the Corvair community of thorough, factual reporting on those occurrences that can impact all of us.
Aerolitellc, Jeff Garrett
Start the year off right. Easy ways to stay in shape in the new year.
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Ben52425(at)aol.com
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| Posted: Tue Jan 29, 2008 7:51 am Post subject: Clarification of the Ocala crank replacement |
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HI GROUP
I FLEW MY PLANE FROM OHIO TO OCOLA FL. WITH NO ENGINE PROBLEM
EXCEPT FOR A OIL LEAK I COULD,T FINE AT THAT TIME LANDED AT OCOLA
TOOK OF AFTER FUELING UP . ON DOWNWIND LEG LOST POWER LANDED
AND GROUNDED THE PLANE.
CALLED JEFF AND HE CAME TO THE RESCUE
THE REST YOU READ IN JEFF,S STATEMENT
WHAT I,M TRYING TO SAY IS THE ENGINE RAN GREAT TILL TAKE OFF
AT OCOLA
PILOT AND OWNER BEN
N524B
**************
Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489 [quote][b]
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