Subject: plugs up
From: ACRE NL
Date: 8/22/2001, 9:29 PM




All right, I 've stood by the side lines long enough.  What ever the
problems there may be with the Plugs Up orientation, oil drain back is

not

one of them.  Consider it for a moment, if anything restricted the

return

oil flow from the central housing to the pan,  to the point that it

"backed

up", then it would only be a matter of moments before the the building

oil

pressure in the center housing would blow past the oil seals.


What pressure Ed? Nobody said anything about pressure.  It is only the oil
level in the rotor we are concerned with. And that, as Jon pointed out,

affects

the cooling of the rotor. Also the oil squirter itself could be affected.


Since it does
not, then there must be a sufficient path for oil return to the pan.

Either

there is an adequate path for oil return or there is not.  If not, then

the

oil will eventually fill the center housing and push past the seals.


I don't think so. I think the main concern with the drain back has always
been the level of the oil in the rotors. Nobody ever mentioned blowing
by the oil seals on here as I recall.


Indications would be copious amounts of smoke just as there is when the

oil

ring seals fail. I have run a Plugs Up installation for 160 hours and no
smoke, others have run them much longer and none have enougher any

problem

with oil drain back.  Other problems perhaps, but not oil drain back.

There

is simple no emperical evidence/data to indicate a problem with oil

drain

back.

 The biggest draw backs of a Plugs Up from my perspective (and I have a
Plugs Up installation) are:



1.   You have to fabricate a special oil pan and suck oil through a

longer

pick up tube.



 2.   Another drawback, is that if you are considering a turbocharger

(and I

am), yes it hangs nicely on the bottom away from other things, BUT, you

will

have to have a scavenger pump to pump the turbo oil back to the oil pan.
Another possible point of failure



3.   An additional, draw back is Tracy Crook's PSRU won't fit (at least

not

without some modifications to the mounting plate).

With the engine in its normal orientation, you do not have to deal with

any

of the above, good enough reasons in them selves to question whether any
perceived advantage of plugs up is worth the effort.  Right Paul? {:>}

So I agree with Paul that there are drawbacks, but from my perspective,

the

only proven draw backs are  installation related.
The reason most of us rotated the engine in the first place was to:



1.  Gain better cowl clearance for some high profile items (such as the

old

distributor and water pump) Not necessary with crank angle sensor  of

today

and if you are willing to trim the water pump housing nozzel - depending

on

your particular airframe requirements.



2.  Place hot exhaust on bottom - ideal for exiting the cowling on an

RV(at

least)



3.  That is the way Lou Ross recommended (and where most of us early

guys

got our PSRU) and at the time had no better source of information.

So bottom line, ask yourself whether you really need to go Plugs Up?

Best Regards

Ed Anderson




Ed, you forgot to mention that engine you cooked. I think your
subconscious is suppressing that memory :-) It was your experience
that really turned me off on plugs up.

Also I might add a tangential muffler replacing the exhaust manifold and a
side exit for the exhaust pipe is ideal for a rotary. Tracy flew for years
with a .035 (0-too thin :-)) stainless steel tangential muffler under the

cowl.

An .049 SS muffler would not be that much heavier and a side exhaust would

allow a

single rad under the engine. A side exhaust is ideal for a turbo needless
to say.

Paul Lamar




You are probably correct about suppressing the cooked engine (one shrunk

rotor), however, many others have now confirmed that getting all the air out
of a rotary (regardless of orientation) is something to pay attention to in
your plumbing design.  I believe Lynn indicated it takes several trips
around the track to get all the air out.

    By the way, I just got a Sony Digital camera like the one you have and
took it on a trip to visit my Great Great Great Great Grandfathers resting
place in Northern North Carolina (circa 1788) and took great photos.  So
nice to see what you have right after you shoot it while you have another
chance to take a better photo.  Should pay for itself in saving development
of film.  Thanks for the suggestion.

   Any word on first article?

Best Regards

Ed Anderson


Not only must you get the air out but the engine must be designed such to vent
any vapor build up. (Notice I did not say "air".) That is where the water outlet
of the block comes in and that is why the outlet must be on top of the block.
Sure you can vent it with auxiliary lines but then you are defeating the design 
of the cooling system in the first place.

They are definitely going to publish it from the sounds of it. Since we mentioned
Reno I think they will try to coordinate it with that report.

Paul Lamar
 
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