I need a break from timing gears, so I am going to turn to the Crankshaft.
I import a scaled drawing and build a crankshaft on top. Notice in the drawing that the two center cylinders are pushed towards the two ends of the bock to make room for the center crankshaft bushing. Also the conrods are offset from the center of the crankshaft journal as well, again to make space for the crankshaft bearings.
As shown below, In my Wallaby engine I used two ball bearings in housings mounted to the end of the crankcase and a bronze bushing mounted in the center of the crankshaft screwed to the upper crankcase half. The ball bearings do not need oil delivered to them, but the center bushing does. This scheme worked well and I am going to use it again and see if I can fit everything in.
My Wallaby engine and its crankshaft and bearing arrangement
I need to add some features to the crankcase for the crankshaft. These are shown in the picture below:
Then I create a sketch to define the dimensions of the crankshaft. Not sure if this diagram is going to make sense to anyone else but me.
I am offsetting the connecting rod journals on the crankshaft 1/16″ to allow for more room for the crankshaft bearings. That is, the center of the connecting rod journals are offset 1/16″ with respect to the center of the cylinders. If I can get rid of this later, I will.
I draw up the crankshaft according to my napkin sketch and drop it in the crankcase. I have to clear some material inside the crankcase to clear the crankshaft webs. The bearing at the back, flywheel end, looks good. The bearing at the front of the engine is going to be a challenge because I also have to deal with the timing gears at the front of the engine.
I am designing a model of the 97 cu In Midget Offenhauser. It was the larger 255 and 270 cu inch Offys that were used in the Indy cars. The MIdget Offy was used in the Midget Racers of the 1930s and 1940s. I guess they still race them today, but that was the heyday.