Inverted engine oil system

[Wobbley Orange]

I have a question regarding inverted engines e.g. Gypsy Major and the like, but the same question applies to the lower cylinders of a radial engine.I can understand the pressure side of the lubrication system and how the scavenge system returns oil from the valve rocker/cam shafts. However, how does the designer prevent the lubrication oil "pooling" in the pistons?
Effectively this type of engine has a set of cups ideally placed to collect oil from the main beaings etc. Does the system depend on the oil being thrown out and collecting elsewhere, or is there a more elegant solution?
Any answers gratefully received.

 

[kmccut]

I had hoped someone might answer this, but since no one did I'll take a crack at it.

What you must understand is that the pistons are moving at something between 2,000 and 3,000 fps, which converts any oil that falls onto the bottom cylinders into a mist. The crankcase interior is designed to accumulate this mist and route it to the scavenge pump(s).
When the engine shuts down, a relatively small quantity of oil may invade the lower-cylinder compression space, which is why the engine is pulled through prior to starting. Normally, unless there is a high-pressure oil pump leak or other path between the oil tank and lower cylinders, the oil quantity is small and the pulling-through process ejects it into the exhaust, forming the gray smoke that accompanies radial and inverted engine starts. In abnormal circumstances, the lower spark plugs must be removed to clear any excessive oil (i.e. hydraulic lock).

 

[Wobbley Orange]

Thanks very much for answering my question, it's much appreciated. I have spent a lot of time peering into sectioned engines in museums trying to work this out - now I know! Thanks for your time.

 

[riggerrob]

Some radial engines also have special oil drains in their lower cylinders.
A few radials even have systems to hold exhaust valves open - during the first few revolutions - to allow excess oil to drain and reduce back-pressure on the starter.

 

[Wobbley Orange]

Thanks Riggerrob, that makes sense, I've not heard about the exhaust valves being held open. I watched a YouTube video on starting a DHC Beaver that had been standing and the pilot took out a sparkplug from the bottom 3 cylinders to drain any oil, which seemed a lot of fuss - a drain plug makes more sense.

 

[kmccut]

Some radial engines also have special oil drains in their lower cylinders.
A few radials even have systems to hold exhaust valves open - during the first few revolutions - to allow excess oil to drain and reduce back-pressure on the starter.

Can you be more specific on both counts?