Wouldent say that now cnbrown, but hell, Im enjoying it!!
Onto the core pattern,
Much the same process again, blank of correct size, centres marked, centres driven home, corners knocked off with planer.
Next, the main points are marked out on the now round blank.
Not forgetting the extra material either end for the ''hanger spigots''.
Taking shape, care is needed at curve area to provide sufficient strength and wall thickness on the finished part.
Nearly done, diameters are checked and the ends narrowed down with the parting tool to make cutting off waste easier.
When held up against main pattern you can now see how the core will look inside the mould.
If you look at the plastic flange two dimples can be seen inside, these are clearance for the bolt heads holding flange to head, I have to make two hollows yet in core pattern to ensure there is sufficient material here after the pour for when I counter-bore the bolt holes. I could make the same two dimples in the main pattern doing away for the need to counter-bore, but Ill be boring the flange holes in a jig anyway so its only a matter of using a stepped counter-bore bit. That way, the flange holes are bored, and the clearance around them is also done at the same time using the stepped bit. You'll see that later anyway, its very simple.
Some of you may be wondering where the groove for the ''o'' ring is, I chose to omit it for a reason, on some heads pitting can occur at the flange area making sealing a problem when using an ''o'' ring, this way, I can face the flanges flat and use a gasket or sealer, or I can machine the groove with a simple mill jig. That way I have options. If you wanted to mould the groove you could very easily by inserting a removable core on that end, but doing it this way I wont need to.
Next up, transferring the core mould to a core box. The core box is basically a box with the shape of the core I just turned inside it. You then pack sand into this box tightly, the box is separated and you then have the core shape replicated, but in sand and ready to place inside mould.
(more to follow)