On 18/8/19 10:25 am, rbowman wrote:
On 08/17/2019 01:06 PM, micky wrote:
Worth noting that car engines have only sleeve bearings, but they get
long life out of them by making them of special material and by
inserting oil under pressure between the bearing and the rotating
shafts.** My guess is that roller bearings and ball bearings wouldn't
work at the high rpm of car engines, or at least they wouldn't work
better, though maybe i'm wrong and some engines I'm not acquainted with
do use them.

FWIW, sleeve bearings are used up to 150,000 rpm. Think turbochargers.
In operation, hydrodynamic lubrication keeps the metallic components
separated by a thin oil film.

Consider what an automotive crankshaft looks like. How do you get the
ball bearings on the journals?

https://www.bmwclassicmotorcycles.co.../crankshaft-2/

Some motorcycles use roller and ball bearings but you are essentially
building the crank out of pieces and the crankcase splits perpendicular
to the centerline of the crank.

They were generally two stroke engines and cars also used them, like the
Goggomobile, early Suzuki LJ 50s and several other Japanese marques of
the same era. Not sure if Saab 2 strokes used built up crankshafts. The
difference was the lack of pressure lubrication so the more usual
hydrodynamic lubrication systems wasn't an option. Two strokes also
needed to fill up dead space in the crankcase so it could be used more
efficiently as a pump. This meant the crankshaft webs were quite bulky
lending themselves to press fit crank pins. roller and ball bearings are
known as anti-friction bearings so were a benefit in small two stroke
engine in reducing the parasitic losses associated with friction.


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)