dxhall Posted March 30, 2012 Posted March 30, 2012 When a motor lets go because of a rod bolt failure, the bolt doesn't usually fail all at once. There's usually a nick or something where the failure starts, and then "beach marks" radiating from the nick. When the break gets far enough through the shaft of the bolt, the remainder of the bolt then lets go all at once. The break in this bolt shows a consistent texture across the whole shaft of the bolt. That indicates to me that the bolt broke all at once, which suggests that the cap failed first, then, when the cap was completely cracked, the bolt snapped.
gstallons Posted March 31, 2012 Posted March 31, 2012 Can you post pics of this rod "assembled" and indicate which is forward as far as the rod/piston relation in the block.
gstallons Posted March 31, 2012 Posted March 31, 2012 When a motor lets go because of a rod bolt failure, the bolt doesn't usually fail all at once. There's usually a nick or something where the failure starts, and then "beach marks" radiating from the nick. When the break gets far enough through the shaft of the bolt, the remainder of the bolt then lets go all at once. The break in this bolt shows a consistent texture across the whole shaft of the bolt. That indicates to me that the bolt broke all at once, which suggests that the cap failed first, then, when the cap was completely cracked, the bolt snapped. There is very little stress on the rod cap other than when the rod is being pulled down during the intake stroke of the crankshaft rotoaion.
68C Posted March 31, 2012 Posted March 31, 2012 Have a look at the Wikipedia entry for crank acceleration, I think you will find the rod cap is most loaded as it slows before getting to TDC and as it accelerates away from TDC, remember this is a four stroke so not always under load from combustion pressure in the cylinder and is pulled down by the other cylinder pressure. http://en.wikipedia.org/wiki/Piston_motion_equations
Orson Posted April 13, 2012 Posted April 13, 2012 Any updates? I'm curious, as I thunked the V11 engine was fairly bullet proof (minus the single-plate clutch issue). 76,000 km (+/- 47,000 miles) on my Tenni.
HaydnR Posted April 13, 2012 Author Posted April 13, 2012 Any updates? I'm curious, as I thunked the V11 engine was fairly bullet proof (minus the single-plate clutch issue). 76,000 km (+/- 47,000 miles) on my Tenni. There is a little more discussion on the wild guzzi forum with the end opinion being that the end cap suffered a fatigue fracture resulting in catastrophic failure. http://wildguzzi.com/forum/index.php?topic=52988.0
luhbo Posted April 13, 2012 Posted April 13, 2012 ... with the end opinion being that the end cap suffered a fatigue fracture resulting in catastrophic failure... That's what it looks like. You can nicely see the rest lines. Nevertheless, such a big lump should be really far away from any fatigue failure. Hubert
Chuck Posted April 13, 2012 Posted April 13, 2012 No production manufacturing process is perfect. This is truly a weird failure, though. You would *expect* the rod bolt to fail, but this doesn't appear to be the case. I don't think I'll be worrying about Rosie or the Mighty Scura doing the same thing..
luhbo Posted April 13, 2012 Posted April 13, 2012 No production manufacturing process is perfect. ... Notch effect?
pete roper Posted June 18, 2012 Posted June 18, 2012 And I for one am happy it wasn't just parted out. Pete
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