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Engine basics => Engine set up tips => Topic started by: frank mccune on October 30, 2020, 08:39:58 AM

Title: Damaged OS .35 Stunt!
Post by: frank mccune on October 30, 2020, 08:39:58 AM

         Dave Eshelman’s post concerning a crashed OS .35 Stunt reminded me of a crashed OS .35 Stunt that a club member brought to a club meeting years ago.

     This engine had the crankshaft pushed out of the rear of the backplate.  To this day, I can not understand how this happened!  That meant that the prop nut threads failed along with con rod and backplate.  This engine was in a stunter so was not going at a fast speed. 

      If anybody has ever seen engine damage that drove the crank through the crankcase, kindly post your experience.

     Be well,

     Frank

Title: Re: Damaged OS .35 Stunt!
Post by: Dave Hull on October 31, 2020, 10:33:23 PM

McFrank,

The threads would not necessarily have had to fail to cause this. For example, if the propeller hub crushed an 1/8th of an inch, the shaft could move back that far. There isn't that much clearance to the backplate, so the crank pin might come thru.

When I was first learning the reverse wingover--the third one I think--I hesitated on the controls and went straight in. Lots of scattered metal in that privy dance. The end of the road for an OS .35FP with only 50 flights on it. And the Lightning Streak it was attached to. That was my first plane in maybe 25 years...?

The Divot
"Scattering debris throughout the finest flying fields in Southern California"

Title: Re: Damaged OS .35 Stunt!
Post by: Brett Buck on October 31, 2020, 10:37:09 PM

Quote from: Dave Hull on October 31, 2020, 10:33:23 PM

McFrank,

The threads would not necessarily have had to fail to cause this. For example, if the propeller hub crushed an 1/8th of an inch, the shaft could move back that far. There isn't that much clearance to the backplate, so the crank pin might come thru.

When I was first learning the reverse wingover--the third one I think--I hesitated on the controls and went straight in. Lots of scattered metal in that privy dance. The end of the road for an OS .35FP with only 50 flights on it. And the Lightning Streak it was attached to. That was my first plane in maybe 25 years...?

The Divot
"Scattering debris throughout the finest flying fields in Southern California"

Also, the case itself could have failed and pushed the entire front housing backwards .Those engines were pretty fragile.

     Brett