Almost too hot to work this weekend but I've made a start on making a one piece idler like the one at the top:
The tank I'm representing for some reason acquired odd idlers. Given the amount of repetitive machining involved, one is enough.
Given the pattern of spokes, the idler will be made in two halves with interlocking hubs. First half underway, blank faced, turned to outside diameter using a custom mandrel for work holding:
Outer rim defined:
First profiling for the spoke webs:
More profiling:
Rear side profiled:
One weekend's work...
Regards.
Stephen