Just back from vacation, and right into the workshop. After riding my motor bike two weeks across Sardegna it's time to be productive again I'm continuing the build process with a not to difficult part. The connecting rod. Made of C45 with RG7 bushes.
Finally I found some time to continue with the Felgiebels. I started making the piston rings. According to the book, Felgiebel itself bought them from a model store, made of cast iron. After finishing a first try ring, it turned out, that the ring must be bent very far to slip over the piston. This is too much for a normal, untreated cast iron. The ring will not spring back into its original position. It will remain deformed and the pressure to the cylinder will be too much, in my opinnion. Fortuntely I used GGG60 cast iron which can be excellent hardened and tempered. The termpering temperature is suprisingly high at about 550°C.
Some time was left, so I continued building the piston. I modified the inner construction compared to the original. Felgiebel turned the inner side, leaving less bearing surface (about 1.5mm each side) for the piston pin and some kind of Pilz (german word) to fix them. I milled an oval to the inner side to give more bearing surface and used the usual clips to fix the pin.
Not finished to far, next step will be to mill the nose.
Next step is to build the contact breaker. I start with the holder, made from 1.5 steel. I welded a package of 4 pieces together for better mechining and to save some time, too. This would be a job for a EDM. But I don't have one. Therefore a mill must do the job.