Wasting time constructively
FARM BOY HIT AND MISS ENGINE
How it was built
This engine is typical of small portable power plants that were used on farms before electric motors became widely available in the early 20th century. This particular engine was designed by Jerry E Howell.
Making a start
The engine is built entirely from bar stock. Some of the machining is complex and requires a bit of thought, I drew and 3D printed this section of the frame before cutting metal.
CRANK SHAFT
The crank shaft is made from a single piece of gauge plate (01 tool steel), this was left in its unhardened state which should be fine in this application. The danger with hardening is that the part is likely to distort. An alternative would be to make it oversize, harden and finally grind to size. Another approach is to fabricate from several pieces and glue and pin together.
The pictures below show the process.
The finished item had runout of less than 0.002".