>Mark - do you have an update on your cam failure, >Rick Human The first part of the saga can be read at http://www.flykr2s.com/failedcam.html . As of right now, my engine is in three different parts of the country and I am basically waiting on a crankshaft to proceed with the rebuild. Under close inspection of the crankshaft which was being used when the cam gear failed, we found, using a high power magnifying glass, that the crankshaft with the gear installed had been cleaned with shot blasting prior to being turned to .020. Blasting a crankshaft and gear for cleaning purposes is acceptable if the correct media such as walnut shell is used. Media, for those who don't know, is the material which is being thrown against an object for cleaning and peening purposes. Steel shot is not a media which you would want to use for cleaning a gear. Steel shot does not have a smooth round surface but is a very tiny piece of metal with ridges and flat sides and not uniform at all. Under a magnifying glass you can easily see the shape of steel shot. This is a very abrasive media and upon being blasted on the crank gear, it left the surface on all of the teeth very damaged. There were pits and ridges on every tooth of the gear which could not be seen with the naked eye. In essence, the crank gear was turned into one big rotating file and it took only 4.5 hours for the steel crank gear to wear the aluminum cam gear down to failure. Considering the cost of a rebuild on an engine, I would say that was a very expensive 4.5 hours of flight. An inspection of a used gear of any kind should be done prior to it's use. A high powered magnifying glass should be part of everyone's tool box. This was yet another learning curve for me and an expensive one. Had I known this before the rebuild, I am sure I would be flying around enjoying the Wisconsin snow scenery especially on a blue sky day like today. I sure hope to be in the air soon as I do love winter flying.
Mark Jones (N886MJ) Stevens Point, WI
