HCI's design utilizes anti-friction bearings for all rotating assemblies. The advantage of this is that oil requirements are low and the engine doesn't react adversely to interruptions in oil flow. The crankshaft's front half rides in a setup similar to an automotive wheel hub. A nut in front of the prop flange keeps the tapered roller bearings firmly on their races.
This is one of the simpler parts to make for this engine, however it requires careful attention to tolerances and detail. On HCI's castings this bearing carrier is integral with the front half of the crankcase. If you were to make a mistake while machining the bearing carrier of a casting you'd end up having to buy an entire front case! Since castings for the seven are not yet available and I'm making the case from billet I chose to make my bearing carrier separate to avoid such a possibility.
After cutting the aluminum round to length I used the four-jaw chuck to face and clean up the work. It's nice to have reliable surfaces to run a dial indicator on should the need arise. Next I drilled a half inch hole through the center of the work. This hole coincides with a half inch dowel on my rotary table. This method allows quick setup of the work while maintaining bore alignment. (Remember I need to bore hole on either side for the bearing cups)
One thing that has delayed me in the construction of my engine is research. Strangley enough, I've developed an intuitive sense of when to proceed. An excellent example of this is the tolerances and finish required for the bearing carrier and the crankshaft. Something kept bugging me about these parts so I kept looking into it. Thank God I didn't jump in and make them! The information I gleaned from the Timken catalog and other good references told me that there is to be a certain degree of interference fit on these parts and their respective bearings. If I would have made the parts to match the bearing's dimensions a sloppy fit would eventually occur. Most of us don't think about the possibility of a bearing's seat turning in it's bore or on it's shaft but it can happen resulting in galling and/or wear. Furthermore if a bearing rides on a shaft with a finish that is rougher than called for it can eventually wear down the microscopic ridges of that part and make it smaller resulting in a poor fit. The same goes for the cup bores in the bearing carrier. Attention to such details make the difference between an engine that lasts or fails prematurely.
I'll have pictures of the finished product soon, For now this exciting round of turned aluminum is it!
