[Diy_efi] Ball Bearing vs. Plain Bearing

[efi student]

"They do; as do other transient consitions where there is insufficient =
oil
flow or shaft speed to sustain a hydrodynamic film.

Ball-bearings are much less susceptible under those circumstances and =
have
low turning resistance from static."

And this would have what net effect on our crank, rods, pistons, cams, =
etc.?
I'm sure lots of people on this list can recognize the symptoms of
lubrication failure on a rod bearing or a piston skirt or in cam =
journal.
We all know that modern engines running modern lubricants have far more
service life than anything built in the 30's.  Start up wear is a really
minor consideration in bearing selection.

Again, I find it impossible to believe that any ball bearing has less =
drag
than a properly sized and  pressurized plain bearing in service, and =
since
this discussion is about turbochargers in service, it seems pointless to
describe situations under which all engine components suffer.

So, I'm back to my original request.  Does anyone (outside of Garrett's
marketing department) have hard data to support the claim that a ball
bearing turbo spools faster than a plain bearing turbo?

Lance

-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On =
Behalf
Of Bernd Felsche
Sent: Wednesday, January 01, 2003 5:04 PM
To: diy_efi at diy-efi.org
Subject: Re: [Diy_efi] This turbo assist stuff, suggestions


On Wed, Jan 01, 2003 at 02:35:20PM -0500, Grant Beaty wrote:
> > Ball-bearings indeed do have lower friction than under-lubricated=20
> > hydrodynamic bearings.

> Yes, we are aware of that. I think more people are worried about=20
> friction during opperating conditions. Or are you implying that=20
> cold-starts can eventually take their toll on plain bearing turbos?

They do; as do other transient consitions where there is insufficient =
oil
flow or shaft speed to sustain a hydrodynamic film.

Ball-bearings are much less susceptible under those circumstances and =
have
low turning resistance from static.

It might be instructive to look at the high-performance engines of the
1930's and 1940's built in Europe. The Auto Union race cars had =
ball-bearing
conrod ends; as did the DB601-engines (IIRC) used in tens of thousands =
of
aircraft - until ball bearings could no longer be obtained. Only then =
did
they change to plain bearings.

--=20
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