Wiped Rod Bearings
Wiped Rod Bearings
(OP)
I recently found some connecting rods for an engine that is out of production, and finding spares is very difficult. The rods are a cast aluminum alloy, without bearing inserts. The rods are OK, except the big end bearing surfaces are scored badly.
Is it possible to rebuild these rods, by machining the big ends and inserting new bearings? Is this ever practiced?
Thanke in advance for any help.
Is it possible to rebuild these rods, by machining the big ends and inserting new bearings? Is this ever practiced?
Thanke in advance for any help.





RE: Wiped Rod Bearings
RE: Wiped Rod Bearings
RE: Wiped Rod Bearings
RE: Wiped Rod Bearings
I see no reason why the rods cannot be resized or machined for modern inserts as long as there is enough material so as not to compromise the strength.
If these old Al rods have been abused, at least have them checked, NDT or Zyglo tested. Even then, it's a crap shoot.
Rod
RE: Wiped Rod Bearings
I assume you are saying that the new bearing surface might just be machined into the existing aluminum without any new insert.
This would be accomplished by milling a few thousanths off the rod to rod cap gap, giving enough metal for machining the new journal surface. Is that correct?
RE: Wiped Rod Bearings
Regards
Pat
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RE: Wiped Rod Bearings
My old Triumph motorcycle had aluminum rods. Caps were steel, though. Bolts were tightened to a stretch value, not torqued. This was a -67 model. Regular bearing inserts.
Dan
RE: Wiped Rod Bearings
RE: Wiped Rod Bearings
RE: Wiped Rod Bearings
You say that the bearing surface has suffered and your description suggests an overheating condition which must have had an effect on the rest of the rod. I would very much advise against remachining old aluminium under such circumstances. If the engine you are rebuilding is rare or expensive my advice would be to install steel rods either forged or cast, here in England there are a number of organisations who can make them for you.I have even heard of rods being converted from one application to that of another but please take great care to do sufficient calculations to ensure reliability.
RE: Wiped Rod Bearings
They were certainly used in the Tiger Moth aircrat engine and I think in the 30/98 Vauxhall.
Many engine bearings are aluminium and many camshafts run directly in an aluminium head or crankcase. Almost every modern 4 valve DOHC engine springs to mind as does the VW beetle.
Regards
Pat
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RE: Wiped Rod Bearings
I can remember boring the big ends of some smaller twins larger for inserts for some customers, or maybe to convert to more common inserts. It cut a long shallow scallop into each of the rod bolts, but those customers said it was a well proven, successful mod.
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RE: Wiped Rod Bearings
Is the Onan engine even pressure-lubricated?
RE: Wiped Rod Bearings
Only problem would be if the rods used studs or bolts to holt the cap on. As the studs will have to be removed before machining properly.
RE: Wiped Rod Bearings
Mike Halloran
Pembroke Pines, FL, USA
RE: Wiped Rod Bearings
there is generally a ramp cut into the upper half which directs the oil so it can effectively form the hydraulic wedge as the crankpin turns
if your resizing removes this ramp, you may not get adequate oil hydraulic wedge formation.
bob g
www.microcogen.info
RE: Wiped Rod Bearings
Hardly seems worth the mess trying to come up with something else.
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RE: Wiped Rod Bearings
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kind of like modern PM rods created by "cracking" a finished rod.
Some US Ford engine had a circular grooved finish cut in main bearing caps and block that looked to locate the cap nicely in 2 directions