Inside of the hubcap after I finished facing it off. It's got a 9 degree taper that I computed using a little trig. I left my scientific calculator at work so I did it the old fashioned way - did the math for a tangent function and then looked up the angle in one of my old books. The outside has a 5 degree taper on it. Likewise on the math. It's amazing what a guy can do with a bar napkin and an old machinist book.
It fits inside the hub just like it was made for it. I still need to drill some holes to fasten it to the wheel but that'll happen soon - maybe today. I can't clamp the hubcap into the three jaw chuck on my dividing head so I made a quickie mandrel to hold it while I drill and spotface the bolt holes. The holes are going to end up right about where the taper and the flat surface meet, hence the requirement to spotface for the bolt heads.
As soon as I get that finished up and I weld the nut on the one end of the axle, I can install the wheel. I should probably paint the parts of the wheel that are in the as cast condition before assembly. Everything else looks pretty nice - no point in half-assing it now. The main thing is - it's fast nearing completion. As soon as the sidecar is done I'll get started on jerking the motor out of the 900 and get busy on the bike itself.
Feeling pretty good about all the progress of late. Just need to keep the fire burnin'.