Not that there is anything at all wrong with John's method, I just decided
I wanted to try a slightly diferent approach.
It came to me while making my hardwood bearing blocks that the same design
can be modified to suit a conrod top. So I went about making them.
I also had some 4mm mild steel rod sitting around so used this to make the
two conrod shafts. I tapped an M4 thread at the bellows end to provide an
adjustable fitting, cushioned by cork washers.
I also picked up some little brass collets with grub screws from a model
shop, which are perfect to finish the half crank for the front bellows.
And I also fitted two of these at the handle end of the crank, one
either side of the end wall to prevent any back and forth movement while