Oil Delivery System
Today I worked on the oil delivery system, including the oil pump and the oil galleries required to deliver oil to top end (Camshafts) and to the crankshaft middle bearing. The engine will have a wet sump oil system, that is oil will be stored in the sump of the engine and then pumped from there to where it is needed. The original engine was of a dry sump design with an external oil reservoir. A dry sump in a model engine is more complicated to implement; it would require two oil pumps, one to return oil to the reservoir and another to deliver oil to the engine bearing surfaces that need it.
Since I have chosen to use a wet sump I will provide an oil splash guard in the sump that separates the rotating crankshaft from the oil sump. The engine has two breathers on the side of the crankcase, I will use one of the breather top caps as a dip stick/oil-fill and the other as an operational breather.
The image below shows the flow of the oil from the sump, through the oil pump, up through a gallery in the crankcase bottom, through a gallery in the crankcase top. At this point the oil can travel one of two ways, continue straight up through the gear tower to supply oil to the camshafts or back through the crankcase to the main crankshaft bearing.
Below the image shows the channel on the back of the timing gear tower that routes oil up from the crankcase to the head. The block forms the other side of this oil gallery, an o-ring surrounds the channel in an attempt to minimize oil leaks as the oil is under a fair amount of pressure.
Below is a diagram showing how the oil makes its way from the crankcase to the internal camshaft gallery.
Today I figured out how get oil distributed throughout the engine. However, I still have a few design issues I need to resolve. Above I show a couple of items that still need to be worked out. Due to the direction of the engine rotation, the oil pump wants to deliver oil to the left side when viewed from the front, but it is difficult to bring oil to the top end on this side because of the gears that drive the distributor in the gear tower are in the way. So the oil pump needs to deliver pressurized oil to the right side of the engine when viewed from the front. There is a loopy path that creates an interference between the oil pump and the front crankshaft bearing holder mounting screws.
Below is a cutaway showing some of the issues still to be resolved. Again, as always, I would like to thank Terry Mayhugh as I have derived many of these solutions from his Offy build.