Oil tanks: Rotaries vs inline & combat damage

[EdStevens]

Another comment in respect of the original question and damage to the oil tank -- looking at the Camel image you posted as representative, the position of the oil tank makes it a very difficult target. It is shielded from the front by the engine and at the rear by the pilot and fuel tank. Only a deflection shot from the side would have much chance of hitting it. I don't think they were actually hit very often.

[FlyXwire]

Romani,

Here's a drawing showing a typical dry sump oil system for an inline engine:

[Dave_Watts]

Hi all,

I'll chime in on the Mercedes D.IIIa as I'm personally familiar with it.

The oil pump does the following;

1. Pump oil (from the oil reservoir in the crankcase of the motor) to the main bearings (of the crankshaft), and up to the camshaft housing.

2. Pump oil into the crankcase reservoir from the auxilliary oil tank. This oil tank was sometimes part of the fuel tank or was a separate stand alone tank.

3. There is a maximum level tube in the crankcase reservoir, any oil that supercedes that level is pulled into the oil pump and pumped out to the auxilliary oil tank. If you had a "tight" motor that consumed very little oil, the action of the oil pump would constantly bring fresh oil into the system and "overfill" the crankcase causing the excess oil to be pumped back out to the auxilliary oil tank, or in other words circulate the oil constantly to and fro from the crankcase reservoir and the auxilliary oil tank.

When Romani started this thread he showed where the Sopwith's rotary had a "pressurized fuel system". The Fokker Dr.I, E.V and other rotary powered Fokkers never had pressurized fuel systems. As I recall, on a Dr.I your instruments as from the factory were ultra-basic consisting of tachometer, compass, and main fuel gauge; there were no fuel pressure gauges.

Did other rotary powered aircraft utilize a pressurized fuel system?

A long time ago I did a thread on the robustness of a rotary powered Dr.I as compared to an in-line powered D.VII, with regards to the D.VII having much more susceptibility with a radiator, pressurized fuel system, and more vulnerable oil, water, air, and fuel system.

As well, all things being equal, when fabricating a replica there is more cost and infrastructure with an in-line water-cooled powered aircraft over a rotary powered aircraft; say a Fokker D.7 as compared to a Fokker D.6.

Best wishes,
Dave

[j ferguson]

Dave,
that's quite a pump you describe. It pulls oil out of the reservoir and sends it to the bearings. Doubtless it has a presssure relief valve like an automobile oil pump so that when the backpressure gets to wherever it's set for, the extra oil goes somewhere else, in this case apparently the crankcase.

Now we get to the part I couldn't understand. If the level in the crankcase gets high enough, the pump sends it back to the reservoir. Is it possible that this pump has two chambers? One scavenges oil out out of the crankcase whenever the level gets high enough and the other chamber feeds the journals?

I ask because I can clearly remember the D3 Crankcase which was in the shop in Glenview Illinois that I worked in in the late 50's and it seemed immense at the time. I always assumed the D3 was a wet sump engine but for all of the many good reasons which have been divulged in this thread, I can see that a wet sump was not a good idea and the system you describe and the one shown on the drawing above would be much more reliable.

Help me with how the pump itself is constructed. Does it have two chambers or are there two pumps bolted together?

best regards, John Ferguson

[Machinbird]

Mr Ferguson, The Mercedes DIIIA oil pump system has four pistons and 3 circulating loops. I am attaching a page from a WWI British exploitation report on the engine which describes the lube system.
Best wishes.
Sid

[j ferguson]

Many thanks for the report. I knew it had to be complicated.

When I used to rebuild cameras I used to think that to a German designer, no problem could not be solved without the application of complex macnhinery. I do love that pump. Tour de Force (sp?)


john Ferguson