> Oiling problems have been mentioned when racing MGB's and many failures
> attributed to lack of oil pressure.But is that so ? How much pressure is
> really needed to avert collapse of main or conrod bearings ?
Um, more than zero, I assure you. :-)
> The other example (tenuous LBC connection ) is of course the Chevrolet
> inline six cylinder ohv engine,made from 1932 to a few years ago,as truck
> and passenger car engine, in countless versions and derivatives all over
> the world.
One derivative of which, BTW, is the very BMC B Series engine we're talking
about.
> is history, as Fangio won 3 times the F1 championship
Five, actually. I've got the years on the T-shirt from the Historics
the year that Fangio was the guest of honor, but they were if memory
serves 1952 (Ascari won in 1951, the first year), 1953, 1955, 1956, and
1957. It might have been '54, but I know that he won at least the last
three of his five championships in succession, and that he retired after
the 1957 season. What was left to win? :-)
As for the rest of your interesting article, I'll note only that there
were also several corresponding developments after the period of time
you mention, notably the thin-walled lead-indium bearing replacing
the babbitted white-metal bearing of the vintage you describe. The
thin-wall bearings were pioneered by Vandervell, and used what was at
the time considered to be a ridiculously thin layer of lead-indium on
a copper shell. Earlier engines used bearings which were in many cases
poured ("babbitted") in place; the Ford Model T, for example, used
such bearings. They were designed for use in low-pressure oiling
systems, or in splash-fed systems, which are characterized by low
brake mean effective pressure (BMEP) and low RPM.
After WWII, engine development has moved consistently toward the goal
of maximizing RPM and BMEP. The Vandervell thin-wall bearing is one of
the enabling technologies (to use a Nineties buzzword) that made this
possible, because with the addition of a high-pressure oiling system,
the thin-wall bearing makes possible higher BMEP and higher RPM than
the otherwise sturdy babbitted/white-metal bearing. The Hirth roller
bearing crank is another way to achieve high BMEP and RPM levels, but
at a very high cost.
I don't know exactly why the earlier bearings worked so well without
constant pressure, whether they just lived with the friction, whether
the crystal structure of the metal was better suited for absorbing
oil, whether the softer metal was effectively sacrificial with very
large tolerances, or whether the RPM and BMEP levels were low enough
to make it livable. I suspect a combination of all these features.
But I can assure you that in a BMC B Series engine of the late Sixties
and up, you *do* need more than 0 PSI of oil pressure to keep the
con rods from eating all the lead-indium off the copper backing plates.
And if you don't want to take my word for it, I'll be glad to send
you a bearing from the #2 connecting rod of a 1972 MGB 18V engine that
suffered momentary oil starvation for your inspection and enlightenment. :-)
--Scott "How much would it cost to mail this to Tasmania, anyway?" Fisher
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