Bent conrod / low hardness / connection?
Bent conrod / low hardness / connection?
(OP)
I've got an engine (diesel) with a bent conrod. Somebody measured the hardness of the rod in the bend region, and found it to be considerably less than spec. I don't generally associate hardness with resistance to buckling, but I'm curious to see whether anyone has another view on the subject (one besides mine and that of the guy who told me the rod bent because the hardness was too low). If you agree with the idea that hardness plays an important role in the bending of a rod, please advise as to how I might incorporate this figure into future buckling cover factor calcs (rod in question had a buckling CF over 2, even at zero speed with exaggerated cyl pressure, by my calcs)...
If, alternatively, you believe that that cylinder probably hydraulically locked, I'd appreciate suggestions regarding where to look for corroborating evidence (pin boss? valve seats?)...
If, alternatively, you believe that that cylinder probably hydraulically locked, I'd appreciate suggestions regarding where to look for corroborating evidence (pin boss? valve seats?)...





RE: Bent conrod / low hardness / connection?
Liquid ingestion from water is possible, but that usually happens to more than one cylinder. Head gasket failure is another, but my first inclination is a leaking injector. Tell tale indicators would be the obvious ones. Check head bolts for stretch, heads for warpage, piston pin bores for egg shape. Check wet sleeves (if equipped) for proper sealing.
Repairing the engine is only part of the service, diagnostics is just as critical.
Franz
RE: Bent conrod / low hardness / connection?
Thanks for the suggestions about items to inspect.
RE: Bent conrod / low hardness / connection?
RE: Bent conrod / low hardness / connection?
The other thing that might be worth checking is that heavily loaded members have a reduced stiffness (and hence a reduced elastic buckling strength) but it is 20 years since I worked on that and don't even have a name for the technique. Tangent modulus comes to mind?
So far as the metal properties of the failed rod, I don't see why failure would cause a softening of the material, I can't remember having come across that before.
Cheers
Greg Locock
RE: Bent conrod / low hardness / connection?
I would have a metallurgist look at the failed rod vs spec, and I would also look for coolant or fuel leaks into that cylinder.
I guess that's stating the obvious
Regards
pat pprimmer@acay.com.au
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