Bust-a-Crank?

Pmerems · #1 10-26-2009, 08:05 PM

Gents,

I thought you might find the following photos interesting.

A friend bought 3 C-150's at a flight school bankruptcy auction. One C-150 was out of annual and had a note in the logbook "rough running engine, alternator removed".

A few months after owning the C-150's my friend decided to start up the C-150 with a replacement alternator. The engine ran rough. He did some initial inspection of the engine and found play between the prop rotation and the accessory rotation. He pulled a cylinder and found the cause of the problem.

It is hard to believe the engine actually ran.

pierre smith · #2 10-27-2009, 05:29 AM

...but it wouldn't have run long that way. The oil was spilling out of the break...notice the blue/heat discoloration? Pretty soon, a rod would have been laying on the block.

Regards,

Brantel · #3 10-27-2009, 05:39 AM

Thats nothin, those airboat guys would weld that sucker up and run it for another 2000 hrs

LarryT · #4 10-27-2009, 12:17 PM

Quote:

Originally Posted by pierre smith

...but it wouldn't have run long that way. The oil was spilling out of the break...notice the blue/heat discoloration? Pretty soon, a rod would have been laying on the block.

Regards,

Note the "beach marks" on the face of the fracture surface. This crack progressed little-by-little until ultimate failure.

Personal note: I cracked a crankshaft in my Super Late Model Stock Car between the first crank throw and the counterweight cheek when I was running in the NASCAR Grand American Division. I had six cylinders running in time with the distributor and the front two that ran out of time due to crank flex. It only happpened at high engine speed and presented as an ignition break-up at the end of the straights. Spent all season trying to diagnose on an electronic scope. Replaced every part in the ignition and fuel system. Cost me a LOT of prize money because I was running pretty good at the time. Never learned what the problem was until the crank finally broke in half idling in the pits. Also learned why the Big Boys pull the motor out and tear it apart when they can't figure out what's wrong right away. Of course you have to have more than one motor for that to be a routine procedure.

Larry