Acceptable conrod cap deformation
Acceptable conrod cap deformation
(OP)
Hi all,
Does anyone know what would be acceptable conrod cap deformation. The big end details are 57mm ID, 30mm wide, 7500 rpm, max force on the cap 35kN. Thanks! Derek
Does anyone know what would be acceptable conrod cap deformation. The big end details are 57mm ID, 30mm wide, 7500 rpm, max force on the cap 35kN. Thanks! Derek





RE: Acceptable conrod cap deformation
RE: Acceptable conrod cap deformation
RE: Acceptable conrod cap deformation
In other words, if I gave you a number you should disregard it.
RE: Acceptable conrod cap deformation
http://fuelpumpsusa.com/AUTOPARTS_PICTURES/ford/f2...
RE: Acceptable conrod cap deformation
Mike Halloran
Pembroke Pines, FL, USA
RE: Acceptable conrod cap deformation
Here is a link to a Mahle presentation about con rod optimization.
http://www.mahle.com/C125708F0068F67A/vwContentByU...
It seems to say 1 or 2 thou of big end distortion is OK, depending upon direction.
But the rod was optimized with this in mind.
• Ideal for Range Extender/Hybrid Applications Ideal for Range
Extender/HybridApplications
• Light Weight Engine Applications
Sounds like engines limited to 3600 rpm or so, and unlikely to ever be allowed under the care, custody, and control of a child,
or someone who acts like a child once in a while.
RE: Acceptable conrod cap deformation
My FEA gave 10 times this which was a shock so I've either done it wrong or I need to beef up the cap a bit
RE: Acceptable conrod cap deformation
... or social- engineer your way into Federal-Mogul and ask a real expert.
Mike Halloran
Pembroke Pines, FL, USA
RE: Acceptable conrod cap deformation
RE: Acceptable conrod cap deformation
It sounds like 1 thou would be ok. I'm still hoping that someone who works in this area will pitch in. cheers, Derek
RE: Acceptable conrod cap deformation
How are you modeling the interface between crank journal and bearing insert?
I think to some extent the rod, especially the cap, will conform to the shape of the journal when highly loaded.
here's some almost useless info about the contours built into rod bearing inserts other than one purpose is to reduce problems when the bore distorts. Sounds like Within 3/8" of the parting line their may be LOTS of extra clearance, which might be helpful in starting the hydrodynamic oil wedge anyhow.
http://www.stealth316.com/misc/clevite-77-rod-main...
http://www.motorheadheaven.com/it_bearinginstall.a...
RE: Acceptable conrod cap deformation
We found the mistake. The deformation was measured from the fixed piston pin so included the stretching of the beam. Measured across the big end diameter, the deformation was 0.7 thou.
Thanks for the links Tmoose. From reading them I can see that I'll need to do some testing of these titanium rods to see how they wear and adjust the eccentricity of the bearings to suit.
cheers, derek
RE: Acceptable conrod cap deformation
Is the big end geometry similar to a successful steel rod? If so, is there room to beef it up a bit?
I'd be concerned that Titanium's lower modulus would automatically make life harder for the rod bolt unless the "foot print" of the parting face is larger
RE: Acceptable conrod cap deformation
RE: Acceptable conrod cap deformation
Bearing races are normally finished very flat and quite smooth. Often bearing seat features are ground, so are likely pretty flat and smooth as well.
I'd wonder about the potential for embedment of the EDM'ed parting faces.
Is there clearance provided at the tips and roots of the serrations?
Since it is unlikely that the final installation preload is just 1/3 of the capabilities of the bolt, I'd be tempted to do a few experiments with multiple tightening cycles or subjecting the rod and cap to clamp loads far greater than the bolts/screws will be able to provide.
FWIW Ford flat head V8 main bearings had a single, curved serration.
http://www.precisionenginetech.com/wp-content/uplo...
Looks like maybe it is created as a single diameter, so it is up to the bolts to keep the cap from skewing.