By Jason Ballamy 
Part six - making the crankshaft and flywheel
M4. C4n

I decided to make the crankshaft next so that it could be used to gauge the bore of the flywheels. Two pieces of 1 x 1/2” bar were machined down to 0.875 x 0.45 x 2.625”.

These were then bored 0.625” for the shaft and 0.563” for the reduced ends of the pin.
Holding them in the 4-jaw a small raised area was formed on opposite sides 0.0125" high giving a finished web thickness of 0.425"
I then popped them onto the rotary table to add a radius to the ends.
I used 5/8" precision ground mild steel for the shaft and pin. These are all the bits ready for silver soldering.
You can see below that the solder was applied to one side only which had a 1/16" deep chamfer around the hole to stop the solder wicking all the way onto the working surfaces and save clean-up time.
A little bit of work with a file and it cleaned up quite well.
For added security some 1/8" holes were drilled and rods inserted ready to be peined over into shallow countersinks
After bashing them over a bit of draw filing restores the surface and makes the rods all but invisible.
With that all done the middle can be cut out and filed flush.
With the crank done the next items are the two 10" flywheels. I just managed to hold them with the 4-jaw chuck bearing onto the inner face of the rim. First operation was to turn the outside face, as the tool overhang was a bit long to start with I used a 16mm boring bar as it was thicker than my largest L/H tool but had to mount it upside down and run the lathe backwards.
Next the side was machined from the inside outwards using the same boring bar but running the lathe in the conventional manner. I took off approx half the waste which equated to 0.100" which seems to be the usual allowance that these iron castings have.
It was then a simple matter to advance the tool to clean up the recessed edge of the rim and counterbalance.
The hub was then trued up using a button tool to give a nice fillet to the internal corner. I always prefer to turn the rim before the hub/bore as if anything is likely to move it will be while the rim is being machined.
The hole was opened out with ever increasing drill sizes to 9/16" and then bored out to the required 5/8" using the crankshaft as a plug gauge for a nice fit.
The flywheel was then turned around to machine the other side, I used two DTIs, one at the top to get it concentric and the small one at the bottom to make sure there was no wobble.
The face of the rim and recess were then machined. The governor side flywheel also needs the area around the hub skimmed smooth. On this flywheel there were a lot of small holes and inclusions which took a lot of effort and one blunted tip to get through but luckily by the time I got down to finished sizes there were very few pits left visible.
The remaining cast surfaces were then given a going over with the Dremel to remove flash and the worst of the cast texture and the governor flywheel drilled and tapped for the weight pivot and spring post.