Neil Clayton wrote:

I'm trying to read everything I can on Lyc engines, since a dinosaur (an
O-360-A4A) has recently taken up residence in my workshop.

The books say that the prop thrust translates into an axial crankshaft
force, which is then transferred to the engine casing via a flange on the
forward end of the crankshaft, just behind the front bearing shells. The
flange runs against a machined face in the crankcase (amazing - no thrust
bearing at all!)

Anyway....all is OK as long as the engine is in the tractor configuration.
But in a pusher config, the prop thrust will have the effect of OPENING

the

space between the thrust flange and the crankcase thrust face.

So....my question is; how is the crank axial thrust transferred in a

pusher

config?

"Perry J. Mick" wrote:

Paul, can you clarify this, an aircraft engine
has no thrust bearings?  Nat's answer lacks any
specifics.

Nat Puffer wrote:

Neil,
Burt Rutan checked this out back in 1980 and determined that there was
no
problem with any model Lycoming in a pusher configuration, and no
problems
have been reported (to my knowledge) in the following 21 years.
Nat

Most piston engines have symmetrical oil pressure fed plain thrust bearings
on the crank so the clearance and size between the front part  and the
back part is the same. This is done because small forces due to minor
machining imperfections  and the oil pressure feed itself might cause
the crank to go one way or the other. I cannot guarantee this however
for the O-360-A4A but I would guess it still applies.

Paul Lamar

The "no thrust bearings at all" is VERY wrong.  All aircraft engines I have seen
have a hydrodynamic thrust bearing at the very large prop bearing.   The
only issue
is whether a pusher aircraft needs a special engine.  At one time Continental
made a "pusher version" of the O-200, but has said that the std engine is OK
for pusher.  This has been proven to be true for all engines tried.   The prop
end main bearing has flanges front and rear, with a thrust flange machined on
the crank in all the cases I know of.  The front side of the first crank cheek
is polished at the bearing and serves as the thrust surface on the crank for
tractor loads.

Bill

Long EZ builder & pilot
BSME, MSME

 
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