I made a thing.
I had some communications with a writer at Model Engineer, and was discussing the shortcomings of the base casting on this model. In the end, rather than wait until later, I went ahead and completely removed the circular boss and the two rails next to it. Those features are way off center and will look horrible if left in place.
As a result, I needed to either make the boss as a new disc on its own - or do as I ended up doing and incorporate the disc into the outboard head.
The head is a circular wedge shaped item - you can see it here in cross section, at the bottom of the cylinder.
I made mine like this, to replace the boss at the same time.
Before I go any further, I want to make it clear that the approach I have taken is one of achieving best accuracy I can, because I felt like it. The wedge feature can be achieved by simple marking out perfectly well - in fact I'm sure the engine would run fine if the head was just made with a flat, non angled face. I just decided to go this route because I find it satisfying.
So first off a piece of 2" steel rod went into the lathe. 2" is the largest diameter I can fit through the chuck and spindle, but that's pretty good - saved me having to saw off a lump and make more scrap. That was turned to a top hat shape at final OD of the part that fits in the cylinder - at .0005" under the nominal diameter of the mating bore (when I get to that).
Incidentally - and this is a bit extravagant but
REALLY nice - the domestic authority desired a new TV in the house so I repurposed the "old" one as a monitor. It is in full view of lathe and mill. I didn't really think it would work out so well but it is unbelievably nice to have drawings magnified right there in view.
So then that was parted off, turned around and the dowel hole put in the back side.
And there is the top hat - all very simple. A fun bit of turning.
The next bit is the more interesting bit. But I have to take the dog for a walk first.
