Today I will be working on the front cover, this is indicated by the arrow in the picture below:
The early Midget Offy’s like the one above hard mounted the front engine mounting plate to the engine as can be seen above indicated by the red circles. The flat plat with the wings on it mounted the engine to the frame. A similar plate is on the rear of the engine. This was a problem because the race cars had flexible frames and the twisting of the frame imparted a twisting load to the engine block and caused them to crack.
The picture below represents a later version of the Midget Offy with the front engine mount removed. It it can be seen that it is no longer bolted to the front of the engine, but is allowed to pivot on the crankshaft cover. This allowed the race car chassis to twist without imparting that twisting load to the engine.
Source: The Miller/Offenhauser For Sale Page
However, we are modeling an earlier vintage Midget Offy so we will have the larger boss for the motor mount rigidly mounted to the front of the engine.
The crankcase needs a little work to blend into the front cover. Below is a wonderful picture of the crankcase without the block and we can get a good view of the shape of the crankcase where it meets the front cover.
Source: In the Shop: 1934 Offenhauser Engine – Update
I create a cocktail napkin sketch of the front cover, more to capture the features I want to create than to get the dimension correct.
Then I start working on the 3D model.
This front cover and crankcase will require some more work. As I add more parts into the assembly model, there are more interactions among them and more time is spent making them all work together.
Here is where I ended up today. It is going to be raining the rest of the week, so I hope to be spending a little time each day continuing the work on the Midget Offy.