Incidentally, babbit bearing don't just need oil under pressure to cool them,
they require pressure to build a wedge on the leading edge of the load area.
And Babbit bearing are not primitive, they are often the best choice for
modern high load applications.
On Sep 15, 2010, at 8:00 AM, Bill Babcock wrote:
> I really doubt that residual oil is sufficient, for the same reason: These
are
> babbit bearing, not rollers. They require oil under pressure to work. A
> residual film doesn't do much, and under the weight of the crank it drains
> away to nearly nothing in a short time. The oil passages seem to do a good
job
> of draining too. Without an accusump there is always a few seconds waiting
for
> the oil pressure to show. I can't see a reason to rely on faith that it's
> sufficient, when all the evidence at hand tells me it isn't. Especially
when
> there's a ready alternative. I don't do many things because "I've always
done
> it that way". I generally have a reason, and in this case it's hard for me
to
> understand where you are headed with this notion.
>
> Seriously, which would you rather do, turn your ignition on and immediately
> see 20 pounds of oil pressure before you start the engine, or turn it on
and
> see no oil pressure for five seconds after the engine started?
>
> On Sep 15, 2010, at 1:21 AM, Randall wrote:
>
>>
>>> While I certainly have not done any scientific testing, I am
>>> completely
>>> convinced that running an accusump greatly extends the life
>>> of my engines.
>>
>> I have no doubt of that. When running under load, those primitive babbit
>> bearings require a constant flow of oil to keep them cool.
>>
>> My question was solely about pre-lubing before startup. Unless you have
>> just assembled the engine without assembly lube, IMO there is plenty of
oil
>> leftover to cover a second or two of idling (meaning very little bearing
>> load, and very little heat generated through bearing losses).
>>
>> OTOH, I understand that you've "always done it that way", and it certainly
>> does no harm. Wouldn't want to take a chance on it actually having some
>> benefit. So carry on, and don't mind me.
>>
>> Randall
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