In article <vines.FRl8+@?>, rtgetzinger@scif.com writes
>Michael,
>I had a spit crankshaft turned down to 0.040" because it was already at
>0.030". I had to drive 1200 miles round trip to get the block that had the
>crank in it and didn't know the condition. I wasn't happy but needed a crank
>at less than catalog prices. I did not have the crank hardened but was warned
>about the life of a crank with 0.040" journals. I suspect maybe 20,000 miles
>of easy driving.
Why? The crankshaft journal has been reduced in diameter by about
0.02% - hardly a major change in its capacity to handle the stress
factors. The depth of the whitemetal bearing material is either
unchanged or increased (normally the latter). Crankshaft journals need
regrinding because foreign matter gets between the bearing surfaces and
scores them, not because they wear unevenly in normal use. The whole
point of whitemetal bearings is that they take up the wear. I don't
understand how having an undersize crankshaft can significantly reduce
its life - but I look forward to being enlightened. :-)
> At 0.050" I don't think you can even get bearings that size.
>Other than use as an anchor I believe its value is that someday it could have
>more metal welded to the journals and then turn that down to have a useable
>crankshaft. Sounds like a last resort though to me and very spendy.
There is a process called Selectron Plating that is specifically
designed to build up undersize journals on shafts - see
http://www.brushplating.com/process.html for details. It is used
extensively in heavy engineering, and provides an excellent and 100%
effective solution, which is a damn sight cheaper than a new shaft (at
least on medium-speed diesel engines and steam turbines!). I am not
sure how the costs would compare to building up a shaft with weld, and
then turning it down, (I'm pleased to say that I have never tried that),
but the quality of the resulting bearing surface would be greatly
superior.
> Have you
>found a source for 0.050" bearings?
I don't know a retail source, but the manufacturer's labels on the box
containing the remaining three pairs read, "COUNTY (R), ENGLAND - CB
6013 050 - MADE IN ISRAEL 01/01" and "CR 448AM 050 CB6013" and the
bearings themselves are stamped "COUNTY REGD. UK C448 050 3E".
ATB
--
Mike
Michael Hargreave Mawson, author of "Eyewitness in the Crimea"
http://www.greenhillbooks.com/booksheets/eyewitness_in_the_crimea.html
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