Primarily for general aviation discussion, but other aviation topics are also welcome.
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#1787656
To qualify about the sealed system. I am talking about the crankase and lubrication system which is the part of the engine being disussed isn't it?....Gurgling...aka oil.
Some people on here seem to just like arguing for the sake of it..!! :roll:
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By Miscellaneous
#1787658
@Shoestring Flyer yes I am in complete agreement. That's why @lobstaboy introducing open valves confused, since it is unrelated to sealed in this context. Seems he confused you too.

However I believe @oldbiggincfi was referring to crankcase and lubrication system in his request of an explanation of your statement.
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By lobstaboy
#1787669
Miscellaneous wrote:@Shoestring Flyer yes I am in complete agreement. That's why @lobstaboy introducing open valves confused, since it is unrelated to sealed in this context. Seems he confused you too.

However I believe @oldbiggincfi was referring to crankcase and lubrication system in his request of an explanation of your statement.


I thought we were talking about the advice not to hand turn an engine that isn't going to be run for sometime? My point being that even if air can't get into the crankcase, it can still get into the combustion chambers, so we need to avoid scraping off the coating of oil on the walls of the cylinders.

OKk not an issue in engines that don't have steel bores.

Anyway since I don't currently fly a Rotax powered aeroplane this is all rather tangential for me, so I'll stop trying (and failing, apparently) to contribute to this thread.
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By Miscellaneous
#1787751
lobstaboy wrote:I thought we were talking about the advice not to hand turn an engine that isn't going to be run for sometime? My point being that even if air can't get into the crankcase, it can still get into the combustion chambers, so we need to avoid scraping off the coating of oil on the walls of the cylinders.

I think I see where the wires are crossed.? My reference to Lycoming and Continental was pointing out that manufactures identify oil can be removed from surfaces which require lubrication by turning the prop. Whether the lack of lubrication results in corrosion over a long period of the engine being idle, or the effects of friction between surfaces requiring lubrication, wasn't my point. Sorry if that wasn't clear, but corrosion was never a topic in this thread as far as I understand. Come to think of it, the point of the thread was nowt to do with 'scraping' the oil off the cylinders either. :oops:
lobstaboy wrote:OKk not an issue in engines that don't have steel bores.

Well, as above, even if there is no iron present and therefore rust is not a problem, any surfaces requiring lubrication between them that don't have sufficient lubrication is not exactly ideal. So for the purposes of the thread the the fact, if it is a fact. the cylinders cannot rust is inconsequential. IF they lack sufficient lubrication it is problematic.
lobstaboy wrote:Anyway since I don't currently fly a Rotax powered aeroplane this is all rather tangential for me, so I'll stop trying (and failing, apparently) to contribute to this thread.

That does surprise me, I had it in my mind you instruct on microlights, I assumed Rotax would be in the mix. My bad, as they say.
By cockney steve
#1787770
Misconceptions abound..... Where do you think the "air" that's gurgling out from the scavenge-pipe, come from? A- from the crank-case, which, unlike a wet-sump engine, does not necessarily have sufficient capacity to take the contents of the "oil-tank" (the dry-sump) As an aside, the scavenge is usually designed to have twice the volume-capacity of the delivery (pressure) -pump)

Piston-rings , even just-fitted in fresh bores, have radial-clearance and vertical clearance. there is also a permanent end-gap, hot or cold. An imperfect seal, when a piston ascends the bore on a compression-stroke, the pressure in the cylinder "leaks" over the top of the ring and then behind it, thus augmenting it's natural spring and pressing it harder against the cylinder wall and the lower face of the ring-groove.

Rotating the engine slowly will allow much greater blow-by, thus pressurising the crank-case and forcing accumulated oil and leakage -gases into the reservoir . AIUI, the Rotax 9-series has no scavenge-pump, relying purely on crankcase compression to keep the oil returning to the reservoir. Even without a breather (or transfer-ports) the crankcase is not"sealed" Admittedly, when stationery, the air -change is low, but even the daily heating and cooling is enough to "pump " air/gas out and as things cool down, suck in atmospheric air which may have a moisture-content high enough to precipitate onto the cold metal.I haven't mentioned,- the "oil-tank /dry-sump / reservoir has to vent to atmosphere, for the system to work. It's a complex problem which Rotax solved and that's why they're now the probable leader in the 80-150 HP market.
cmoreflyer, oldbiggincfi, Sooty25 and 1 others liked this
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By Miscellaneous
#1787801
cockney steve wrote:Misconceptions abound.....

Don't they just. It's not so much the misconceptions I find worrying, we all have those, as their denial and the refusal to even consider that they may have an incorrect understanding. Never mind engaging in civil dialogue. Throw in the accusations and snide remarks directed at anyone questioning those misconceptions and trying to help and it makes me wonder. :roll:

Interestingly I have been having email dialogue with someone who is reading the thread, but not contributing and indeed a benefit of knowing exactly how much oil is in the system has been proposed. :thumright:
Aerials liked this
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