Thanks guys. I find Elmer's engines fun to do while considering "What's next" questions.
Eric - I started with a 1" wide, over length piece of 1/4" aluminium flat bar. Simply used a length of 1" diameter rod as a form/mandrel, my vise and dead blow hammer to bend the arc. As the sides got closer together, I clamped the rod into the "pocket" being formed to ensure the circular shape was maintained. As the sides approached the intended distance apart, I used a couple of blocks machined to the inside dimension to gauge and control the bend.
Once the plan view shape looked good, I put the part in the milling machine vise with the above blocks used as spacers and the part "level". Then the top and bottom surfaces could be surfaced back to be flat and to the target height all around. (I didn't have any 5/8" material suitable for the base so used 1/2" for the base and made the U-shaped piece 7/8" tall.)
The bearing block locations were machined and drilled after the U-shaped piece and outboard bearing support were bolted to the base. The assembly could be clamped in the vise and this ensured a consistent height and alignment at all 4 bearings.
Charlie
