Don.
On page 143 of your Skizzenbuch I am afraid you have misunderstood the luboil system as you have connected the gravity drain from the main engine to the suctionside of the stb.attached lubeoilpump. I guess a description of the luboilsystem would clarify the matter.
The luboil system is based on two independent systems, for each engine, being able to interconnect if needed. It works on a dry sump principle, meaning each engine have a separate systemtank under the engine. Below is an image of the normal and alternative operations. Normal operation of the port engine is as follows: the port systemtank holds the lubeoil for the port engine and the attached lubeoil pump takes its suction (green) via a normal NR footvalve in the tank. The discharge ( red having a reliefvalve with drain (blue) to the systemtank), goes to the distribution box between the engines passing a NR valve b. Valve a1 is open and allows the oil to flow via the main oilfilter with differentialmanometers to the port oilcooler having a dirty oil pipe(blue) via cock f to the port systemtank. After the cooler the oil passes a selector cock c1, in this case normally selecting the port engine. After that cock is a small pressureline to the servomotor for the governor on the camshaftdrive side (aft) of the engine. The servomotor shuts down the engine in case of lubeoilpressure failure and assists the governor in moving the fuelrack. The discharge pipe continues on the front of the engine to a pressure reductionvalve,( rembember the small red wheel?) reducing the pressure from 3kg/cm2 to 1,5 kg/cm2 before it branches off to the main bearings, camshaft drive and supercharger. When the lubeoil has passed the enginecomponents, gravity takes the oil through drainpipes (blue) to a selectionbox to port or stb systemtanks, where port in this case, normally is selected. The attached lubeoilpumps can not take suction via the drain system.
In case of an attached luboil pumpfailure, the quickest and easiest way of an alternative would be to use the aux. electric driven lubeoilpump. The system on my image is self explaning, I guess, and as a last alternative you are able to use the stb. attached lubeoil pump, which system you`ll find on my image as well.
Tore