The pulleys and shafts are fairly straight forward although there is some close tolerance required on the shafts.
Next up, the exhaust valve housing and mounting the cylinder block.
I turned the housing from some brass, I was hoping for bronze but none to be had when I was ready for it. This piece threads into the support plate, it will need some thread locker on assembly to keep it in place.
The cylinder block, which I made on my Taig in fall of 2014, was marked up for holes on 3 sides. 2 are tapped for the spark plug and carburetor, the other is the exhaust port.
With the shafts for the cranks ready, it is now time for the webs and crank pins.
The webs were machined to 25mm from 1” stock. The shaft hole was drilled to 5.5mm and then reamed out to 6mm to fit the shafts closely. They will be attached with Loctite 603 (or more likely the affordable alternative from Weicon). Cutting off went quite well, having a strong lathe makes this so much less traumatic. The webs gave me some challenges as they are only 6mm thick after cutting them off the raw stock. Holding these straight in the 3 jaw was not easy but I ended up using a piece of 6mm rod in the tailstock chuck to align the web. This let me face the second side and reach the 6mm target dimension.
With more parts to make, there are more tools to make 🙂
In making the main shaft, which mounts the flywheel and the exhaust valve, I needed to cut 3 flats 120 apart. From my stash of metals I dug out some hex and bored, then reamed for 10mm. A set screw finished that tool off. While cutting the 2.5mm slot in the end I broke the cutter.
After drilling the base plate, the next item was to drill the supports to the same pattern. This was a bit nerve wracking as there is not much wiggle room for ‘adjustments’.
To align the holes in middle of the supports I used a .375 rod in the mill arbor, and a parallel to make it align with the top surface of the support. The spindle was then in the middle, the vertical was then locked into place. The other position was aligned each time with a spotting drill and then drilled 4.2 for the m5 SHCS.